AME5170 Evaluation Board User Guide
Contents
1. current higher efficiency and reducing stress on the internal MOSFET Low DCR inductor also can increase average efficiency Calculate the required inductance by the equation below The recommended value of inductor for AME5170 application is 2 2uH 22uH L gt tour m men V bronE Tor F CL min 7 4 Board Layout Considerations High frequency switching regulators require very careful layout of key components in order to get stable operation and low noise A good PCB layout could make AME5170 working perfect to achieve the best performance 7 5 PCB Layout Example The PCB layout example is for standard step up converter application with AME5170 device It proves this EV board can achieve reliable performance It follows the layout guidelines below 7 5 1 Use a ground plane under the switching regulator can effectively minimize inter plane coupling 7 5 2 Using 20mil wide track for GND as wide as possible and all GND nodes are as close as possible 7 5 3 The SW node schottky diode and output capacitor Cout1 and Cout2 signal path should be kept extremely short 7 5 4 The feedback components R1 R2 R3 and C1 must be kept close to the FB pin of U1 to prevent noise injection on the FB pin trace and keeping far away from SW node crac l4 T So S3029 2 ERI 2F 302 Rui Guang Road Nei Hu District Taipei 114 Taiwan Tel 886 2 262 868 Fax 886 2 2659 2989 886 2 2659 9 5 Rev B 01 2010 AX AME Inc Zcie2. 1 2 Duty Cycle amp Output Current According to input and output voltage to calculate duty cycle and switching frequency Selecting feasible inductance can calculate output current by following equations m Vo UT V piopk a Vin Vo UT V piopE i Vow Voy cLayp X ps ony max Dx Viv Vow Load max 1 D x U croi E 2 fL Where j VIN is input voltage Vour is output voltage Torr is the duration of switch off for AME5170 Torr is fixed 400ns VpioDE is the forward voltage of Schottky Diode Vsw is switch current limit times switch on Resistance See the datasheet to have L is the inductance f is the switching frequency ILOAD max means the maximum ability of output driving i L4 PT RAE 302 HR HE 2F 302 Rul ae Road Nai Hu District Taipei 114 Taiwan Tel 886 2 282r 8687 Fax 886 2 25559 2889 856 2 2659 975 Rev B 01 2010 ax AN AME Inc zz 3 ALAGIRA Bl 7 2 Capacitor Selection 4 fuF input capacitor can reduce input ripple For better voltage stability to increase the input capacitance or using LC filter is able to achieve 1uF output capacitor is sufficient to reduce output voltage ripple For better voltage filtering ceramic capacitors with low ESR are recommended X5R and X7R types are suitable to select because of their wider voltage and temperature ranges 7 3 Inductor Value Calculation A larger value of inductor will reduce the peak inductor current resulting in smaller input ripple
3. AX AME Inc ZiteTfE Z Brod RA 9j AMEN om snm ERI M AME5170 Evaluation Board User Guide 1 General Descriptions The AME5170 is a fixed off time step up DC DC converter with integrated N channel Power MOS It s ideal for LCD panels requiring high efficiency with light load condition as well as LED application for cellular phone back lighting PDAs and other hand held devices 2 Features e Input voltage 1 5V to 5 5V e Duty ratio Fixed 400ns Torr PFM control e Current limit and Enable functions e Built in internal SW N channel power MOS 3 Applications e LCD Bias Supplies e Handheld Devices e Portable Applications 4 Evaluation Board Schematic 4 1 AME5170 Typical Schematic Cin1 Cin2 EN i I rad 11941 e Output voltage Vin to 28V e Oscillation frequency Various base on I O spec e Thermal shutdown function e Small SOT 25 Package e White LED Back Lighting e Digital Cameras 2 Vout R1 C1 R2 Cout1 Cout2 R3 Figure 1 E 8 pii y 23027 re i 2F 302 Rui Guang Road Nai Hu District Taipei 114 Taiwan Tel 886 2 262 868 Fax 6886 2 2659 2889 886 2 2659 9757 Rev B 01 2010 A AME Inc zziz 4 2 AME5170 Typical Schematic for 20V Application D1 L1 30V 0 2A 10uH 20V R1 REN FLA U1 SW SOS 100K AMES170 Cin R2 Cout1 4 7uF FB 33K 1uF EN R3 OR Figure 2 5 Bill of Materials BOM for Item 4 2 Component Qty Value D
4. escription PartNo Manufacturer Package Cin Coutt Ren R R2 1 33ka ChipResstr RMIOFTN330 TAI 0800 R3 1 om ChipResistor__ RMIOJTNO TA 085 GaNEWNEC CUEN ANW WEZ w D EPE 30V 0 2A PFM Micro Power AME5170AEEVADJZ SOT 25 Boost Converter BlankPCB BlankPCB TM080104 Rev D Rev TM080104 Rev D Vin Vout Copper Pillar GND GND Switch TS 0068 5 190g HSUAN YI o Plastic Screw S 306 PINGOOD 4 Spacer Support PINGOOD Emi LIA MADE 230259 2 HH 2F 302 Rul iux Rond Nai Hu Dietrict Taipei 114 Taiwan Tel 886 2 262 7 868 Fax 886 2 2659 2989 886 2 2659 9757 M Rev B 01 2010 AN AME Inc Zeist Rein RA n ll et ERR M 6 Operating Instructions 6 1 Connect Vin to the positive point of DC power supply and GND to supply ground 6 2 Connect Vout to the positive point of E load and GND to supply ground or parallel an appropriate resistor to pull up the loading 6 3 Importing a logic signal to EN pin will enable the AME5170 Logic high VEN gt 1 5V switches on AME5170 logic low puts it into low current shutdown mode 7 Application Information 7 1 Setting Output Voltage amp Current 7 1 1 Output Voltage The regulated output voltage is set by an external resistor divider R1 and R2 in Figure 2 from the output to the Veg pin and is determined by R 1 Vour Vig X X Where Veg 1 23V for AME5170 2 7
5. fS z Brod RA 9j GND n mT ULE ER Test Pin GND GND Cin2 Vout Vout FB R3 1 feno GND R3 1 C1 7 esl R2 SW D Vout R3 D1 vout Q Screw amp Spacer 4 Places Figure 3 7 6 Freewheeling Diode Selection The freewheeling diode conduction time is longer than the N channel Power MOS off time Therefore the diode parameters improve the overall efficiency Using schottky diodes as freewheeling rectifiers reduces diode reverse recovery time and the voltage drop across the diode is lower For this design choice RB520S 30 with 30V reverse voltage 0 2A forward current and around 0 4V forward voltage drop The freewheeling diode should be place close to the SW pin of the AME5170 to minimize noise coupling due to trace inductance CAETH 14 mE See 302 ee 2F 302 Rui Guang Road Nei Hu District Taipei 114 Taiwan Tel 886 2 262 868 Fax 886 2 2659 2989 886 2 2659 9757 UU Rev B 01 2010
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