AME5150 Evaluation Board User Guide
Contents
1. Vinis input voltage Vout is output voltage TorF is the duration of switch off for AME5150 Torr is fixed 400ns Voiope is the forward voltage of Schottky Diode Vsw is switch current limit times switch on Resistance See the datasheet to have Lis the inductance f is the switching frequency ILOAD max means the maximum ability of output driving 3 5 Rev A 01 2010 AX AME Inc Z2HEFEOSRAA oo EE O E E S AA 7 2 Capacitor Selection 4 7uF 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 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 AME5150 application is 2 2UH 10uH L gt Vov Crew V ope xT OFF 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 PC2. AX AME Inc Z2HEFEOSRAA EE O E E S ANA AME5150 Evaluation Board User Guide 1 General Descriptions The AME5150 is a fixed off time inverting 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 Output voltage Up to 28V e Duty ratio Fixed 400ns Torr PFM Control e Oscillation frequency Various Base on I O Spec e Current Limit and Enable Function e Thermal Shutdown Function e Input Under Voltage Lockout e Small SOT 25 Package 3 Applications e Electronic Information Organizers e Palmtops e Cellular and Portable Phones e Portable Audio Systems e Various Multi function Power Supplies 4 Evaluation Board Schematic 4 1 AME5150 Typical Schematic D1 R2 Vout U1 AME5150 NFB Figure 1 1 5 Rev A 01 2010 4 2 AME5150 Typical Schematic for 25V Application L1 c3 R7 3 3V 4 7uH 0 47uF OR 25V D3 D5 R6 30V 0 2A 2 OR Figure 2 5 Bill of Materials BOM for Item 4 2 PartNo Manufacturer Package c1 1 4 7uF 6 3v Ceramic Capacitor 1206B475K6R3C c3 1 0 47uF 25V Ceramic Capacitor 0805B474K250C 15pF 50V Ceramic Capacitor 0805B150K500C 1 RM10FTN4703 RM10FTN2492 2 RM10JTNO 0805 SD52 4R7 R 4 7uF 50V Ceramic Capacitor _1206B475K500C WALSIN 1206 Schot
3. B layout could make AME5150 working perfect to achieve the best performance 7 5 PCB Layout Example The PCB layout example is for standard Inverting converter application with AME5150 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 C8 signal path should be kept extremely short 7 5 4 The feedback components R4 R5 and C7 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 4 5 Rev A 01 2010 AX AME Inc Z2HELFEOSRAA a oO a ea oO zZ o m so a oE HE Vout O GND 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 AME5150 to
4. minimize noise coupling due to trace inductance 5 5 Rev A 01 2010
5. tky Diode RB520S 30 ROHM EMD2 PFM Micro Power AME5150AEEVADJZ ME SOT 25 Inverting Boost ME Blank PCB TM091101 Rev A Vin Vout Copper Pillar Vout GND 3 YD TECH _ 1x40 12MM Pare Plastic Screw S 306 PINGOOD ae a Spacer Support H 6 pincoop 2 5 Rev A 01 2010 AX AME Inc Z2HEFEHOSRAA oe EES O E E S ANA 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 AME5150 Logic high Ven gt 1 5V switches on AME5150 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 R4 and R5 in Figure 2 from the output to the Vnes pin and is determined by R Vour Vara x 50 Ry x veg 5 Where Vyrfg equals 1 23V and InFB equals 2uA for AME5150 7 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 ae V prone Vin p Voor T Vbrope Vow Vow Leryp X Rps Oonymav Dx Vin Voy 2 fL LAD max 1 D x H croin Where
Download Pdf Manuals
Related Search