Usage of Three-Terminal Regulators UM
Contents
1. The GND pin of each three terminal regulator is driven in Vout common by the operational amplifier output t Favorable tracking characteristics are obtained by B making Ri Re Moreover bias current errors also can uPC741 be canceled if the resistor R1 Re is added between the non inverting pin of the operational amplifier and GND R Re Re Vout O 14 Positive and negative dual power supply circuit This is a positive and negative dual power supply that using positive voltage three terminal regulators uses two positive voltage three terminal regulators D and De are low forward voltage diodes that are absolutely necessary They prevent output voltage Pate pulldown due to discrepancies in the startup timing of O each regulator ZI AD O GND zz D E Vour 15 Wired OR When connecting the outputs of two or more three terminal regulators do it so that voltage from outside is not added to the regulator output at D1 and Ds Vint Di Vour De and D are connected to compensate for the lowering bi gt i t o of output by D and Da De Vine Ds Da User s Manual G12702EJAVOUM 21 5 PRECAUTIONS ON APPLICATION Do not use a three terminal regulator under temperature conditions or voltage conditions that exceed the ratings Other precautions that are specific to three terminal regulators are shown below 5 1 Shorting Input Pins and Ground Pins When a capacitor with a2. Cour Dz Caution Make sure that no voltage is applied Set this value according to the length of the line between the regulator and INPUT pin Be sure to connect Cin to prevent parasitic oscillation Use of a film capacitor or other capacitor with excellent voltage and temperature characteristics is recommended If using a laminated ceramic capacitor it is necessary to ensure that Cin is 0 1 HF or higher for the voltage and temperature range to be used Be sure to connect Cour to prevent oscillation and improve excessive load regulation Place Cin and Cour as close as possible to the IC pins within 2 cm Also use an electrolytic capacitor with low impedance characteristics if considering use at sub zero temperatures If the OUTPUT pin has a higher voltage than the INPUT pin connect a diode If the OUTPUT pin has a lower voltage than the GND pin connect a Schottky barrier diode to the OUTPUT pin from external Users Manual G12702EJAVOUM 13 Figure 4 2 is an example of a standard connection for obtaining a positive and negative power supply The diodes between output and GND are for preventing latchdown at startup and are absolutely necessary in the case of loads shown by solid lines Without the diodes current flows in the separation regions between elements as described in chapter 2 and the output voltage does not rise refer to Figure 4 3 Figure 4 2 Sample Standard Circuit Connection Dual Power Supply
3. without short circuit protection Using the fact that the current flowing out from the GND pin of the three terminal regulator is practically constant add Zener diode to the GND pin to raise only the Zener portion of the voltage R supplies idling to the Zener It also is possible to use a resistor but this is inferior to the Zener from a stability standpoint D is needed as load short circuit protection In addition the input voltage must be set within a range that holds the voltage difference between input and output to the ratings even on a short circuit 6 High input high output voltage circuit Note with short circuit protection Vout O D2 Vin Q2 Vompoe Re Qi 1kQ Ri K Ci 4 7 kQ i 4 Di A ZD TT This circuit combines circuits 4 and 5 The circuit made up of Q Q2 and D is a preregulator The output voltage is as follows Maur VOREG VD 4d ud e e pens ree gend 4 7 De protects against reverse bias in the GND and OUT pins on a load short circuit Note D or ZD must be selected so that the voltage difference between input and output of the three terminal regulator is kept within ratings even on a load short circuit In addition D2 must have low forward voltage 18 Users Manual G12702EJAVOUM 7 Remote shutdown circuit Control the output voltage using a preregulator set up ahead of the three terminal regulator The control input is as follo
4. 0 C W By substituting Pp max VDIF max x lo max 3 6 W in expression 6 3 find the thermal resistance Gis needed in the radiator Ts TA D as Rit c Gu Determination of size of radiation board From expression 6 4 the design objectives can be satisfied using a radiator of 6 1 C W Figure 6 5 shows the relationship between the thickness surface area and thermal resistance of an aluminum board By using a 3 mm thick 60 cm aluminum board here we know that the radiation board will have the necessary thermal resistance Sample use without radiator The junction temperature T in the used state when not installing a radiation board is the following Tu Rthi A X Ppcfa nnt n nnen AEAEE RR EE EEEEEEESAEEEEEEEE EEEE EEEE Ennen EEEa 6 5 Dua Thermal resistance between junction and ambient air still air natural convection Pp Power consumption TA Ambient operating temperature Setting Tu to 100 C or less in the used state is recommended Users Manual G12702EJAVOUM Precautions when installing in a radiator e Make the convexity or concavity of the part installation surface of the radiator 0 05 mm or less e Spread silicon grease to a uniform thickness between the radiator and part Determine the kind of grease on consulting the maker of the radiator e Painting the radiator black increases its effectiveness in radiating heat However if it is close to a heat source it has the re
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6. A startup circuit therefore is set up and it biases the active load at power on to cause normal operation to begin whether the temperature of the transistors is low or high Overcurrent protection circuit This is a protection circuit for preventing the load current from exceeding the current capacity of the output stage power transistor It restricts the base current of the output stage power transistor by biasing the current restriction transistor more deeply in accordance with the voltage drop in the current detection resistor inserted in the load current route Stable operation area SOA or ASO restriction circuit The stable operation area restriction circuit operates to squeeze the output current if the voltage between input and output voltage between the collector and emitter of the output stage power transistor becomes large so that the stable operation area of the output stage power transistor is not exceeded If the voltage difference between input and output exceeds the breakdown voltage 7 to 8 V of a Zener diode connected between input and output it restricts the base current of the output stage power transistor by biasing the current restriction transistor more deeply using the breakdown current Since the larger the voltage difference between input and output the more the base current of the output stage power transistor is restricted the load characteristic is a foldback type drooping characteristic as a result Figure 3 4
7. Output Positive voltage 3 terminal regulator Negative voltage 3 terminal Load regulator Cm Co Cin Co As in the sample circuit for a single power supply load these are needed Absolutely necessary for loads shown by solid lines in which a load current flows from 14 Dit Dit Diz Di Vout toward Nour This is to prevent regulator output on either side from being latched down by differences occurring in the rise of regulator output voltage due to smoothing circuit capacitor capacity differences or the like Note that these are not specifically needed in the case of only those loads shown by dashed lines As in the sample circuit for a single power supply load these sometimes are needed depending on the application circuit Users Manual G12702EJAVOUM If the output pin becomes a lower potential than GND the P type separation region and n type output pin NPN transistor enter a forward bias state and the parasitic transistor shown with dashed lines is formed When this occurs it is connected to the adjacent transistors and does not operate normally Figure 4 3 Sample Power Supply IC Cross Section Diagram Latchdown Separation Output region Q NPN transistor NPN transistor 2 Variable output voltage type When a voltage not included in a fixed output voltage type is needed or the output voltage is to be adjusted and used even a fixed output volta
8. and also includes its majority owned subsidiaries 2 NEC Electronics products means any product developed or manufactured by or for NEC Electronics as defined above M8E 02 11 1 2 Users Manual G12702EJAVOUM The mark shows major revised points Users Manual G12702EJAVOUM CONTENTS INTRODUCTION BE 5 BASIC STRUCTURE OF A POWER SUPPLY IC s eeseeeseseeeeeeeeeee ener nnn nnn 5 2 1 Str cture of a Bipolat IG rect e a Reseed e tt Tet ie aedes 5 2 2 About Power Supply IC Equivalent Circuits nennen nene 6 BASIC CIRCUITS OF A POWER SUPPLY IC eese ENNEN seen nnne nnne nnn nnn 7 3 1 Basic ere 7 3 2 Operating Principles of Variable Output Tvpes nemen nennen nennen nnn nnns 11 3 3 Operating Principles of Low Saturation Tvpes rennen nnns 12 POWER SUPPLY IC APPLICATION CIRCUITS eeeesee eee esses eese enne nennen nnn 13 WANNE Elte Mee Tee DEET 18 4 2 Application Circuit Set i eee ea e etd 17 PRECAUTIONS ON APPLICATION eeeeseeeeeneeeeeeen eese nenne nena nnne REENEN nnmnnn nnmnnn nnn nnn nnn 22 5 1 Shorting Input Pins and Ground PINS seise ienien e aaa e nennen nennen neret e nnns 22 5 2 We due Kee NEE 22 5 3 Applying Transient Voltage to Input Pims eene nnne nnne 23 5 4 Reverse Bias Between Output Pin and GND Pin 23 5 5 Precautions Related to Low Saturation Tvpes nennen nennen nnnm nnns 24 5 6 Thinking on Various Protection Ci
9. circuit protection Lu PC7805A Vomeoi 210 Q RD6 2EB 11 Variable output voltage circuit 7 to 30 V 12 Tracking regulator circuit ViNn O Splits the fixed output voltage Voreq of the three terminal regulator using Ra and Rs and compares with the output voltage Vout value split using Ri and Ra The output voltage can be represented as follows Ra Vout x VoREG X Ra Rs This is analogous to the circuits shown in 5 and 8 Since it uses op amplifier PC741 with a single power supply the lowest value of the output voltage can be no lower than the sum of the output saturated voltage of the 4UPC741 and the output voltage of the three terminal regulator A tracking regulator is configured using a power transistor with one positive voltage three terminal regulator The positive voltage is the fixed voltage of the three terminal regulator The negative voltage can be changed arbitrarily by the split ratio of R and Rz Thus the negative voltage output is as follows Vout D protects against reverse bias between the base and emitter of the transistor at power on 20 Users Manual G12702EJAVOUM 13 Tracking regulator circuit This power supply has superior tracking characteristics due to using an operational amplifier and one positive and one negative voltage three terminal regulator
10. current at which the overcurrent protection circuit operates It is defined as the output current when the output voltage is lowered by 2 or 5 from its initial value As described in chapter 3 the overcurrent protection circuit operates together with the stable operation area Moreover note that lopeak decreases as temperature increases negative temperature characteristic Figure 6 4 shows the lopeak Vin Vo characteristics of the PC7800A Series For a nonlinear load such as a motor or lamp select a power supply IC that has sufficient leeway 5096 or less of normal characteristic graph Output short circuit current loshort This is the current that flows when output is short circuited to GND Since most NEC Electronics power supply ICs have an on chip stable operation area restriction circuit the following relation holds if input voltage is high loshort lOpeak Like lopeak loshot displays a negative temperature characteristic Refer to Figure 6 4 for temperature characteristics of the output short circuit current and changes with respect to input voltage Figure 6 4 Sample lopeak Characteristics uPC7800A Series lopeak Vin Vo characteristic Peak output current lopeak A 0 5 10 15 20 25 30 35 Voltage difference between input and output Vin Vo V 6 4 Design Methods 28 A Input circuit design Determine the capacity of a smoothing capacitor of an input circuit using
11. even momentarily under any usage conditions or test conditions Moreover it is a mistake to think that use at the absolute maximum ratings is possible Design should be performed so that even in an abnormal state the equipment being considered leaves room for the absolute maximum ratings In addition it is assumed that GND is the lowest potential in the case of a positive output power supply and that INPUT is the lowest potential in the case of a negative output power supply see chapter 2 6 2 Recommended Operating Conditions If used under these conditions it is possible to obtain output voltage precision as expected Think of this as a criterion for selecting a power supply IC 24 User s Manual G12702EJAVOUM 6 3 Electrical Specifications NEC Electronics guarantees the minimum values and maximum values of electrical characteristics at the time of shipment Therefore whether or not it is possible to satisfy the specifications of the power supply to be designed must be determined by adequately investigating each rating and condition in each item of the electrical characteristics Each item of the electrical characteristics is described below Since the explanations below are mainly for positive output power supply ICs reread them while reversing polarities for negative power supply ICs 1 Output voltage Vo This item is the most important rating in using a power supply IC Pay attention to measurement conditions If power supply specific
12. large capacity is connected to the load of a three terminal regulator if the input pin is shorted to GND or the power supply is turned OFF the voltage of the capacitor connected to the output pin is applied between the output and input pins of the three terminal regulator Figure 5 1 a b Discharge current Vout The withstand voltage between the output and input pins of a three terminal regulator is approximately 0 7 V for a low current with the output transistor base emitter voltage Therefore a diode like the one in Figure 5 1 b is effective against the reverse bias of the input and output pins Figure 5 1 b is for a positive voltage regulator The diode direction is reversed for negative voltage 5 2 Floating Ground Pins Do not make the GND pin of a three terminal regulator floating in the operating state If it is made floating an input voltage that has not been stabilized is output unchanged This is because the output stage power transistor is biased by an overvoltage protection Zener or current mirror transistor leakage current Since IC internal overheat protection and the like do not operate normally in this case there is a possibility of destruction if the load is short circuited or on an overload Be particularly careful when using a socket 22 User s Manual G12702EJAVOUM 5 3 Applying Transient Voltage to Input Pins A three terminal regulator is destroyed if a higher voltage than the rating or a vol
13. operation cannot be expected since the PN junction enters a forward bias state and the separation state between the elements cannot be maintained For example when using a positive output three terminal regulator the GND pin always must be made a lower potential than the potential of other pins 2 2 About Power Supply IC Equivalent Circuits Equivalent circuits that are shown in data sheets are so designated assuming the premise of the preceding section that separation regions and substrate are made the lowest potential Be careful not to reference these when this premise is violated 6 Users Manual G12702EJAVOUM 3 BASIC CIRCUITS OF A POWER SUPPLY IC 3 1 Basic Circuits Although the basic circuits that make up a power supply IC differ according to the product type the following elements are necessary 1 Reference voltage circuit 2 Error amplifier 3 Active load constant current circuit 4 Output stage power transistor 5 Startup circuit The following protection circuits also are on chip lt 6 gt Overcurrent protection circuit lt 7 gt Stable operation area SOA or ASO restriction circuit lt 8 gt Overheat protection circuit Figure 3 1 shows a block diagram of a power supply IC Figure 3 1 Power Supply IC Block Diagram 0O INPUT Y Y Y source P circuit Y Output power Startup Reference transistor circuit voltage NN 1 O OUTPUT Error ampli
14. shows the parts of a general overcurrent protection circuit and stable operation area restriction circuit Figure 3 4 Sample Overcurrent Protection Circuit and Stable Operation Area Restriction Circuit uPC7800A Series Stable operation area restriction circuit o INPUT PEN aV l l l TTN l l 4 K A T dw Qie SSN N D St Qv NS SA 4 V Output transistor Ld Qis Current restriction transistor R11 Current detection resistor e e O OUTPUT Users Manual G12702EJAVOUM 8 Overheat protection circuit The overheat protection circuit prevents destruction of the IC by cutting off output if the temperature of the chip itself increases too much Figure 3 5 shows the parts of an overheat protection circuit Q12 which is biased to the extent that it is not ON in a normal operating state is completely ON at 150 to 200 C accompanying a decrease in Vse when the temperature of the chip increases When Q12 is ON it cuts off the output voltage by absorbing the base current of the output stage power transistor Figure 3 5 Sample Overheat Protection Circuit PC7800A Series ig O INPUT K ou C Ee d O OUTPUT GE Q12 Overheat protection transistor e e O GND The overheat protection circuit is designed to operate at temperatures exceeding the absolute maximum rating generally 150 C Therefore if the overheat protection circuit has operated the IC should b
15. PNP Transistor NPN transistor PNP transistor Separation region Separation region E Separation region Collector Base Emitter AE poete p Emitter kc x I r r 2 1 a F H aL x P type substrate Users Manual G12702EJAVOUM 5 Figure 2 2 Structure of Resistor Base diffused resistor Base pinch resistor Separation region O A O Separation region Resistor EPitaxial layer Resistor d diffusion Resistor P type diffusion en ayer deet fetch electrode Bee electrode electrode layer l C IND i i i Bech region region e P type substrate Figure 2 3 Structure of Capacitor Junction capacitor MOS capacitor i i i i i Thin Separation region Separation region T ie Separation region x Al electrode X P type substrate P type substrate There is a point to heed in applying power supply ICs It is that a method known as junction separation is used as the method of electrically separating each of the elements above By connecting a separation region so that it is formed by a P type semiconductor and is the same lowest potential as the substrate the element region and the separation region are electrically separated and insulated by being in PN junction reverse bias states If for some reason the potential of this separation region becomes a higher potential than the element region for example the NPN transistor collector region in Figure 2 1 normal
16. To our customers Old Company Name in Catalogs and Other Documents On April 17 2010 NEC Electronics Corporation merged with Renesas Technology Corporation and Renesas Electronics Corporation took over all the business of both companies Therefore although the old company name remains in this document it is a valid Renesas Electronics document We appreciate your understanding Renesas Electronics website http www renesas com April 1 2010 Renesas Electronics Corporation Issued by Renesas Electronics Corporation http www renesas com Send any inquiries to http www renesas com inquiry 24 NC S AS 10 11 12 Notice All information included in this document is current as of the date this document is issued Such information however is subject to change without any prior notice Before purchasing or using any Renesas Electronics products listed herein please confirm the latest product information with a Renesas Electronics sales office Also please pay regular and careful attention to additional and different information to be disclosed by Renesas Electronics such as that disclosed through our website Renesas Electronics does not assume any liability for infringement of patents copyrights or other intellectual property rights of third parties by or arising from the use of Renesas Electronics products or technical information described in this document No license express implied or otherwise is g
17. an O H Shade graph or simulator so that the minimum value of the input voltage is not lower than the measurement conditions of output voltage At this time connect a film capacitor between input and GND of the power supply IC separate from the smoothing capacitor to prevent abnormal oscillation refer to the data sheet of each product type for capacitor values Users Manual G12702EJAVOUM B C Output circuit design Check whether the load current used is a current no greater than the peak output current Connect a capacitor for abnormal oscillation prevention between output and GND of the power supply IC If transient load stability becomes a problem make sure the capacitor is connected in parallel Radiation design The junction temperature can be calculated using the following expression IP Ese EE M bdo KEE 6 1 Duo Thermal resistance between junction and case 6c Hs Contact thermal resistance includes thermal resistance of insulation sheet when using insulation sheet KI Thermal resistance of radiator Pp Internal power consumption of IC Pp Viu Vo x lo Vin x Ipias TA Ambient operating temperature Expression 6 1 is the calculation expression when using a radiator When not using a radiator such as in the PC78L00J Series use the following expression EHE REA qni E EE 6 2 Use the values in the data sheets for Rin c and Rtnw a in expressions 6 1 and 6 2 Since Tu Rinu o Pp and Ta are give
18. ations are within this range of conditions the expected precision for example 5 is obtained see Figure 6 1 Figure 6 1 Output Voltage Conceptualization For PC7805AHF Guaranteed Range Inside Broken Lines Output voltage Vo V 50 0 50 100 150 Junction temperature T C 2 Input stability REGiN When the input voltage increases the output voltage also increases This item shows how much the output voltage changes when the input voltage Vin is varied within the measured conditions As shown in Figure 6 2 output voltage changes nearly linearly with respect to input voltage Therefore it is possible to infer how much the output voltage will change from the initial period when the initial input voltage is changed to a given input voltage Users Manual G12702EJAVOUM 25 26 Figure 6 2 Input Stability REGin Conceptualization For PC7805AHF Vin 10 V Standard 30 20 o E x E E z 10 z mt ol LLI tr Ke 5 ze 0 5 a E 10 Ta 25 C lo 500 mA 205 5 10 15 20 25 Input voltage Vin V 3 Load stability REGL Whereas REGm is the change in output voltage with respect to input voltage load stability REGL shows the change in output voltage with respect to load current output current When load current increases output voltage decreases nearly li
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20. e considered to have been exposed to an abnormal state and positive use of the overheat protection circuit should be avoided so a separate circuit is needed to perform power supply overheat protection 3 2 Operating Principles of Variable Output Types A variable output type uPC317 uPC337 differs from a fixed output voltage type in that it uses a method for configuring an output voltage setting voltage circuit externally so that an arbitrary output voltage can be set externally Figure 3 6 is the block diagram of a variable output voltage type The output voltage is controlled by comparing the voltage between external resistors Ra and Ra and the reference voltage Vrer in the error amplifier Moreover each block is connected between INPUT and OUTPUT and the current needed in each block circuit operating current is output from the OUTPUT pin Therefore the outflow current from the ADJ pin becomes negligible and its affect on the output voltage value can be ignored User s Manual G12702EJAVOUM 11 Figure 3 6 Variable Output Type Block Diagram M O INPUT Current Protection Source circuit Startup circuit OUTPUT Reference voltage source VREF Gen Rs See 2 setting Vo Ra circuit 3 3 Operating Principles of Low Saturation Types All of the power supply ICs discussed so far use Darlington connected NPN type transistors in the output stage Therefore the voltage difference between input and output that is n
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22. eeded to operate these power supply ICs cannot be lower than the voltage between the base and emitter of the Darlington connected output transistor 0 7 V x 2 1 4 V A low saturation type power supply IC makes it possible to operate with a small voltage difference between input and output by using a PNP transistor as the output stage transistor refer to Figure 3 7 Figure 3 7 Differences Between General Power Supply IC and Low Saturation Type Output Stage Configurations a General power supply IC b Low saturation type power supply IC IN O O OUT INO A ME ae V ae ps Oo GND Oo Oo GND Configurations other than this are nearly identical to a general power supply IC Figure 3 8 shows a block diagram 12 User s Manual G12702EJAVOUM x Figure 3 8 Low Saturation Type Block Diagram 4 POWER SUPPLY IC APPLICATION CIRCUITS 4 1 Standard Circuit Connection 1 Fixed output voltage type t O INPUT Stable operation area restriction puni circuit a Output power circuit Drive transistor circuit OUTPUT Qyerneat protection 5 1 circuit Overcurrent restriction circuit 4 A A o GND Figure 4 1 shows an example of a standard circuit connection Check the data sheet for each product type for the values of input and output capacitors Figure 4 1 Sample Standard Circuit Connection Single Power Supply Output D Cin
23. ertain use conditions Further Renesas Electronics products are not subject to radiation resistance design Please be sure to implement safety measures to guard them against the possibility of physical injury and injury or damage caused by fire in the event of the failure of a Renesas Electronics product such as safety design for hardware and software including but not limited to redundancy fire control and malfunction prevention appropriate treatment for aging degradation or any other appropriate measures Because the evaluation of microcomputer software alone is very difficult please evaluate the safety of the final products or system manufactured by you Please contact a Renesas Electronics sales office for details as to environmental matters such as the environmental compatibility of each Renesas Electronics product Please use Renesas Electronics products in compliance with all applicable laws and regulations that regulate the inclusion or use of controlled substances including without limitation the EU RoHS Directive Renesas Electronics assumes no liability for damages or losses occurring as a result of your noncompliance with applicable laws and regulations This document may not be reproduced or duplicated in any form in whole or in part without prior written consent of Renesas Electronics Please contact a Renesas Electronics sales office if you have any questions regarding the information contained in this document or Renesas Electro
24. fic quality grade applies only to NEC Electronics products developed based on a customer designated quality assurance program for a specific application The recommended applications of an NEC Electronics product depend on its quality grade as indicated below Customers must check the quality grade of each NEC Electronics product before using it in a particular application Standard Computers office equipment communications equipment test and measurement equipment audio and visual equipment home electronic appliances machine tools personal electronic equipment and industrial robots Special Transportation equipment automobiles trains ships etc traffic control systems anti disaster Systems anti crime systems safety equipment and medical equipment not specifically designed for life support Specific Aircraft aerospace equipment submersible repeaters nuclear reactor control systems life support systems and medical equipment for life support etc The quality grade of NEC Electronics products is Standard unless otherwise expressly specified in NEC Electronics data sheets or data books etc If customers wish to use NEC Electronics products in applications not intended by NEC Electronics they must contact an NEC Electronics sales representative in advance to determine NEC Electronics willingness to support a given application Note 1 NEC Electronics as used in this statement means NEC Electronics Corporation
25. fication circuit Re lt Split resistor Ra 77 GND Users Manual G12702EJAVOUM 7 The operation of each block is explained in simple terms below 1 Reference voltage circuit The reference voltage circuit which determines the output voltage of the power supply IC is an extremely important part within the circuit The method for configuring this circuit is as follows e Band gap reference method Use the forward characteristic between the base and emitter of the transistor The possibility of making the reference voltage 2 V or less is a feature of this method Figure 3 2 shows the principles of the band gap reference method Figure 3 3 is a simple circuit diagram of the band gap reference reference voltage used in the PC7800A Series Figure 3 2 Band Gap Reference Circuit V l H2 KT Re Vrer Vaga Bs q In el Wack SO Rs Co Ko Ri R2 Rave O GND The reference voltage is as follows Vrer Vees Ic2 IB3 x R2 R VBE3 AVBE IB3 x Re R3 R VBE3 ee KT wf pp PPP T TEE E 3 3 3 q Hi The temperature coefficient is as follows K R Nrer Nees ee In Re pr 3 2 4 aT aT q Rs Ri By optimally choosing the ratio of B x P2 a temperature compensated reference voltage is known to be obtained Rs Ri Users Manual G12702EJAVOUM Figure 3 3 Simplified Band Gap Reference Circuit of PC7800A Series O ViN 0 VREF rR EK
26. ge type can be used by floating the GND In a low saturation type case it cannot do as described later but voltage precision and drift become a problem A variable output voltage type is useful in such cases Figure 4 4 shows an example of the standard connection Since a bias current for the operation of each block inside the IC flows from INPUT to OUTPUT as described in section 3 2 be careful of the load current By selecting 240 Q as R1 as in the sample standard connection even when there is no load no problems arise since a current of 1 25 V 240 Q 5 2 mA flows to OUTPUT Users Manual G12702EJAVOUM 15 16 Cin Co Caps Ri R2 Figure 4 4 Sample Standard Connection Circuit Variable Output Power Supply Remark This example is for a positive voltage For a negative voltage uPC337 D1 and capacitor polarity are reversed Since there may be oscillation if the wire leading from a smoothing circuit to a three terminal regulator is long 15 cm or more add a capacitor near the input pin For an application in which the load current changes suddenly add a 10 wF or more capacitor for output voltage transient response improvement and add 10 xF to Cap at the same time Connecting a 10 wF capacitor parallel to Re can improve the ripple removal rate approximately 20 dB and increase oscillation stability In this case diode D1 is needed for to prevent application of backward voltage on an output sho
27. has an actual range that is 5 to 6 times the three terminal regulator rating 2 High output current circuit This is an expansion of circuit 1 Current detection is with short circuit protection performed using Ra Therefore since the current at Q1 is restricted by VBE2 limax R2 the output current is as follows Ri 6 Q Qe M QUT Jonas H MAX IREG MAX s GND Ci ji Ce SC IBEG MAX oireann eorr xa he rape 4 3 2 3 High output current circuit D cancels Ver at Q1 with short circuit protection Q and three terminal current distribution is determined by R and R2 Vin Ri 0 4 Q Qi lo Vour O o aZ Re 29 R692 Je Ri Re loqax R X IlREG MAX ANEN 4 5 1 gt IN OUT D GND Cic C2 Caution Absolutely do not connect output pins in parallel to increase the current capacity of a three terminal regulator If the output voltage becomes unbalanced certain ICs operate in a restricted current vicinity and current hardly flows in certain ICs and furthermore the current may flow in reverse Also refer to 15 Wired OR Users Manual G12702EJAVOUM 17 4 High input voltage circuit ViN Ri This circuit can be used when the input voltage exceeds the rating Vin Van Ris eo ee EE 4 6 lout max IBlAS MAX NFeE1 MIN Moreover if the load current changes little a resistor can be used 5 High input high output voltage circuit
28. ie lt 2 gt Error amplifier o GND This circuit controls the output voltage by detecting and comparing the reference voltage created by the reference voltage circuit and the resistor split output voltage If Vout is the output voltage and Vrer is the reference voltage refer to Figure 3 1 the following relationship holds VOUT SmrCOVREFhceeececeucccueccesneveucccueecnsueveuescneecusueveseseusecs B 1 A Here A is the open loop gain of the error amplifier and G Ra Ra Re lt 3 gt Active load constant current circuit Expression 3 1 becomes the following if the open loop gain A of the error amplifier is sufficiently large compared to 1 Vout Vner B A small bias current and high resistance are realized by using a constant current circuit in the error amplifier load to make A 60 to 80 dB 4 Output stage power transistor The output stage power transistor supplies current to the load Although normally a Darlington form NPN the low saturation type of power supply IC uses a PNP single transistor Users Manual G12702EJAVOUM 9 10 5 6 lt 7 gt Startup circuit A power supply IC has an on chip constant current circuit for use as an error amplifier load or for biasing the reference voltage circuit A constant current circuit which consists of paired transistors does not begin to operate as long as the diode connected transistors are not in a steady bias state
29. lam com Europe NEC Electronics Europe GmbH Arcadiastrasse 10 40472 D sseldorf Germany Tel 0211 65030 http www ee nec de Sucursal en Espana Juan Esplandiu 15 28007 Madrid Spain Tel 091 504 2787 Succursale Francaise 9 rue Paul Dautier B P 52 78142 Velizy Villacoublay C dex France Tel 01 3067 5800 Filiale Italiana Via Fabio Filzi 25 A 20124 Milano Italy Tel 02 667541 Branch The Netherlands Boschdijk 187a 5612 HB Eindhoven The Netherlands Tel 040 2445845 Tyskland Filial P O Box 134 18322 Taeby Sweden Tel 08 6380820 United Kingdom Branch Cygnus House Sunrise Parkway Linford Wood Milton Keynes MK14 6NP U K Tel 01908 691 133 Document No G12702EJAVOUMOO 10th edition Date Published June 2005 NS CP k NEC Electronics Corporation 2000 Asia amp Oceania NEC Electronics Hong Kong Ltd 12 F Cityplaza 4 12 Taikoo Wan Road Hong Kong Tel 2886 9318 Seoul Branch 11F Samik Lavied or Bldg 720 2 Yeoksam Dong Kangnam ku Seoul 135 080 Korea Tel 02 558 3737 NEC Electronics Shanghai Ltd Room 2509 2510 Bank of China Tower 200 Yincheng Road Central Pudong New Area Shanghai P R China P C 200120 Tel 021 5888 5400 NEC Electronics Taiwan Ltd 7F No 363 Fu Shing North Road Taipei Taiwan R O C Tel 02 2719 2377 NEC Electronics Singapore Pte Ltd 238A Thomson Road 3112 08 Novena Square Singapore 307684 Tel 6253 8311 G04
30. n find the thermal resistance of the radiator amp 4s from them using expression 6 1 Figure 6 5 shows the thermal resistance of an aluminum board Since the makers of radiators produce radiators suited to power supply ICs also consult the radiator maker Figure 6 5 Thermal Resistance of Aluminum Board radiation board Gus C W Thermal resistance of 1 10 20 50 100 200 500 1000 Surface area of radiation board A cm If T is not within the design values return to A or B and recalculate An example of radiator design is shown next Users Manual G12702EJAVOUM 29 1 2 3 Design objectives Positive power supply using uPC7805AHF Maximum output current lo max 0 6 A Maximum voltage difference between input and output Vor max 6 V Maximum ambient operating temperature TA max 60 C Maximum junction temperature TJ max 100 C Radiation board thermal resistance calculation In a used state the junction temperature Tu is the following Ty m Pin ecy s 648 X PD TA geste tise tii Ere ee il erie ten acelin deta 6 3 Rinu c Thermal resistance between junction and case amp s Thermal resistance between case and radiator Gus Thermal resistance of radiator Pp Power consumption Here TJ max 100 C Ta max 60 C amp c us lt lt 1 C W and Rinu c 5
31. nearly The output voltage for an arbitrary load current can be inferred in the same way as REGin see Figure 6 3 Users Manual G12702EJAVOUM Figure 6 3 Load Stability Conceptualization For uPC7805AHF lo 500 mA 10 i e 0 E z iri uz 6 E S 2M xv 10 gm g oc o Ee 9 d 20 gt 30 Ta 25 C Vin 2 10V 0 0 5 1 0 1 5 Output current lo A 4 Circuit operating current Ibias This is the bias current needed for each internal block of a power supply IC to operate It flows from input toward GND Applications that adjust output voltage by inserting a resistor in GND take this item into account 5 Circuit operating current change Alsias This shows the change in Isias when the input voltage or load current changes 6 Ripple removal rate R R The ripple voltage that appears in the output when a 120 Hz sine wave minimum value and maximum value of sine wave are noted in measured conditions is input in the input is represented by the following expression R R 20 log Vin Vorippie dB If the frequency increases R e R decreases mainly due to the frequency characteristics of the internal error amplifier of the IC lt 7 gt Output noise voltage Vn This shows the noise that occurs inside a power supply IC mainly thought to be thermal noise Users Manual G12702EJAVOUM 27 8 Peak output current lopeak 9 This is the
32. nics products or if you have any other inquiries Note 1 Renesas Electronics as used in this document means Renesas Electronics Corporation and also includes its majority owned subsidiaries Note 2 Renesas Electronics product s means any product developed or manufactured by or for Renesas Electronics 434 NE SAS User s Manual Usage of Three Terminal Regulators Document No G12702EJAVOUMOO 10th edition Date Published June 2005 NS CP K NEC Electronics Corporation 2000 Printed in Japan The application circuits and the circuit constants in this document are only examples and not intended for use in the actual design of application systems for mass production The information in this document is current as of June 2005 The information is subject to change without notice For actual design in refer to the latest publications of NEC Electronics data sheets or data books etc for the most up to date specifications of NEC Electronics products Not all products and or types are available in every country Please check with an NEC Electronics sales representative for availability and additional information e No part of this document may be copied or reproduced in any form or by any means without the prior written consent of NEC Electronics NEC Electronics assumes no responsibility for any errors that may appear in this document e NEC Electronics does not assume any liability for infringement of paten
33. ranted hereby under any patents copyrights or other intellectual property rights of Renesas Electronics or others You should not alter modify copy or otherwise misappropriate any Renesas Electronics product whether in whole or in part Descriptions of circuits software and other related information in this document are provided only to illustrate the operation of semiconductor products and application examples You are fully responsible for the incorporation of these circuits software and information in the design of your equipment Renesas Electronics assumes no responsibility for any losses incurred by you or third parties arising from the use of these circuits software or information When exporting the products or technology described in this document you should comply with the applicable export control laws and regulations and follow the procedures required by such laws and regulations You should not use Renesas Electronics products or the technology described in this document for any purpose relating to military applications or use by the military including but not limited to the development of weapons of mass destruction Renesas Electronics products and technology may not be used for or incorporated into any products or systems whose manufacture use or sale is prohibited under any applicable domestic or foreign laws or regulations Renesas Electronics has used reasonable care in preparing the information included in this document
34. rcuits nennen nennen nnne nenne nennen 24 POWER SUPPLY IC DATA SHEET APPEARANCE AND DESIGN METHODS 24 6 1 Absolute Maximum Ratings ane eri RENE CERE EEN EES FEE ERR Enn 24 6 2 Recommended Operating Conditions 24 6 3 Electrical Specifications ete ctun detache redeo deed e Ee ve dee yea 25 6 4 Design Methods 2 o one i HE e ce cep irt e HP IO be A ee 28 User s Manual G12702EJAVOUM 1 INTRODUCTION NEC Electronics produces a variety of ICs for power supplies that differ in their on chip functions and usage Within these large quantities of three terminal regulators have come to be used to configure stabilized power supplies easily using few external components However the occurrence of unexpected irregularities when designing power supply circuits also has increased Therefore this manual starts with the basic structure of the main bipolar process that is used in ICs for power supplies and gives precautions pertaining to actual applications 2 BASIC STRUCTURE OF A POWER SUPPLY IC As mentioned in chapter 1 a power supply IC mainly uses a bipolar process Understanding the structure of an IC that uses a bipolar process also is useful for applications 2 1 Structure of a Bipolar IC The following elements can be made into an IC in a general bipolar process NPN transistor PNP transistor Resistor Capacitor Figures 2 1 through 2 3 show the structure of each Figure 2 1 Structure of NPN Transistor and
35. rt circuit These are resistors for setting the output voltage The output voltage Vo is determined as follows v d x VREF lap x R2 1 x VREF Ri Table 4 1 shows the relationship between typical output voltages and Re Table 4 1 Settings of Output Voltage Setting Resistor R2 Output Voltage Vo V Re Setting Q Note TYP values 3 Low saturation type The standard method of use is the same as for a general fixed output voltage type see Figure 4 1 However the capacitor connected to the output must have a greater capacity than in a general power supply IC In addition note that the output voltage cannot be adjusted by inserting a resistor or the like in the GND pin as described later Users Manual G12702EJAVOUM 4 2 Application Circuit Set This circuit set mainly is filled in for positive output voltage three terminal regulators However the circuits also can be applied to negative voltage three terminal regulators by changing the polarity of parts employed In the case of the circuit which has connected an element to GND pin it is inapplicable to a low saturation type 1 High output current circuit Drives the base of an external transistor using a three without short circuit protection terminal regulator Here Ri is determined as follows Veet IREG MAX hFEKMIN Ve RB InEe vax 4 2 lo NFE1 MIN IREG MAX In this circuit the output current
36. tage more than 0 5 V lower than the GND pin is applied to the input line In cases in which such voltages are superimposed on the line add a surge suppressor using a Zener diode or the like Figure 5 2 a b 5 4 Reverse Bias Between Output Pin and GND Pin Figure 5 3 a b External protection diode In the sample application shown in Figure 5 3 a the voltage of the Zener diode is applied between the output and GND pins of the three terminal regulator when the load is short circuited Inside the three terminal regulator a diode like that shown in Figure 5 3 b apparently is formed but if a current flows in this part the three terminal regulator is sometimes destroyed Therefore when using a GND like that shown in Figure 5 3 a in a floating state it is necessary to add a low forward voltage diode from the GND pin of the three terminal regulator toward the output pin Users Manual G12702EJAVOUM 23 5 5 Precautions Related to Low Saturation Types Since a low saturation type of power supply IC uses a PNP transistor in the output stage particular care is needed In a low input state before the output voltage enters regulation state such as at startup a large circuit current flows because the output stage transistor is saturated Depending on the product the circuit current is decreased at startup by an on chip rushing current prevention circuit but even in this case a relatively large circuit current flows compared
37. to normal operation For details refer to the Circuit operating current at startup lsias s rating of each product Thus care is needed in the following matters e On startup be careful of the output capacity of the power supply on the input side and the output impedance since a circuit operating current flows in the input superimposed on the load current e t is not possible to adjust the output voltage by inserting a resistor or the like in the GND This is because the circuit operating current increases at startup Be sure to connect a low impedance type capacitor to the output to increase stability against abnormal oscillation 5 6 Thinking on Various Protection Circuits NEC Electronics power supply ICs which have on chip overcurrent protection circuits stable operation area restriction circuits and overheat protection circuits are very difficult to destroy in their normal operating state Nonetheless you should not design circuits that put too much confidence in these protection circuits These protection circuits are for protection against sudden accidents To the best of your ability avoid operating protection circuits for long stretches of time In particular be careful using the overheat protection circuit since this is like operating at a temperature exceeding the absolute maximum rating 6 POWER SUPPLY IC DATA SHEET APPEARANCE AND DESIGN METHODS 6 1 Absolute Maximum Ratings This item shows values that must not be exceeded
38. ts copyrights or other intellectual property rights of third parties by or arising from the use of NEC Electronics products listed in this document or any other liability arising from the use of such products No license express implied or otherwise is granted under any patents copyrights or other intellectual property rights of NEC Electronics or others e Descriptions of circuits software and other related information in this document are provided for illustrative purposes in semiconductor product operation and application examples The incorporation of these circuits software and information in the design of a customer s equipment shall be done under the full responsibility of the customer NEC Electronics assumes no responsibility for any losses incurred by customers or third parties arising from the use of these circuits software and information e While NEC Electronics endeavors to enhance the quality reliability and safety of NEC Electronics products customers agree and acknowledge that the possibility of defects thereof cannot be eliminated entirely To minimize risks of damage to property or injury including death to persons arising from defects in NEC Electronics products customers must incorporate sufficient safety measures in their design such as redundancy fire containment and anti failure features e NEC Electronics products are classified into the following three quality grades Standard Special and Specific The Speci
39. verse effect of absorbing heat e Use one of the insulating board bushings shown in Table 6 2 e Cuta screw in a radiator and absolutely do not use self tapping screws to install one When installing a radiator if the tightening torque of a screw is too great the fins can be distorted and the IC damaged Drive screws using a torque driver that can manage the tightening torque Table 6 1 Three Terminal Regulator Tightening Torque TO 126 0 2 to 0 4 TO 220 0 3 to 0 5 MP 45G 0 3 to 0 5 Figure 6 6 Standard Installation Method for Radiation Board Insulation 3 M screw 3 M screw Flat washer eee c Flat washer cp DE Insulating board 7 p Insulating bushing c Spring washer Radiation board Radiation board lt Flat washer Mk 3M nut Spring washer LLII 3 M nut MP 45G TO 220 Table 6 2 Recommended Insulating Bushings and Insulating Board Product Name Quality of Materials Incombustibility Insulating bushing 25K bushing U Gelanex 3310 Light brown UL 94V 0 Insulating board MP 25 insulating board A Colorless transparent px Users Manual G12702EJAVOUM 31 For further information please contact NEC Electronics Corporation 1753 Shimonumabe Nakahara ku Kawasaki Kanagawa 211 8668 Japan Tel 044 435 5111 http www necel com North America NEC Electronics America Inc 2880 Scott Blvd Santa Clara CA 95050 2554 U S A Tel 408 588 6000 800 366 9782 http www nece
40. ws At H Output At L Output interruption In addition D1 is added to prevent reverse bias between the input and output pins of the three terminal regulator Remark H High level L Low level Control ow Rs This circuit moderates the rise time of the output voltage At power on this is the three terminal regulator s specific output voltage after which it gradually rises to its final value The initial output voltage is Vo REG Vo VorEo The output voltage after stabilization is A Vo REG Vo final value Vos Vorec Hi lgias RSR Furthermore the delay can be represented as follows if expecting up to 9996 of the final value Vo REG T amp CR In 0 01 s Delay time T Power on 9 Variable output voltage circuit The Zener diode in the circuit shown in 5 is replaced by without load short circuit protection a resistor Vo REG Vo REG Vout Vonggg Ri lpas 2 C2 Use a voltage difference between input and output that li is within the three terminal regulator ratings For a load short circuit or capacity load the diode shown using dashed lines is needed and in particular a low forward voltage is needed Note that applications using the variable output three terminal regulator PC317 are superior in output voltage precision and stability Users Manual G12702EJAVOUM 19 10 Variable output voltage circuit 0 5 to 10 V without short
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