PAM2841 EVB User Guide PAM2841EV Board User Guide AE Department 1. Revision Information Date 2008/03/19 2013/01 Revision V1.0 V1.1 Description Initial Release Update EVB Schematic and View Comment 2. EV Board Schematic Figure 1 3. EVB PAM2841 EB7CFA Description PAM2841 EB7CFA evaluation board is a fully assembled and tested circuit board that evaluates the PAM2841 white LED driver. The circuit operates from 2.5V to 5.5V and drives white LEDs in series with a constant current. This application note contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice. No liability isassumed as a result of the use of this product. No rights under any patent accompany the sale of the product. PAM2841 EVB User Guide 4. EV Board View LED+ LED- Figure 2 EV board operational sequence: a. Connect ENA to high (Vin) b. Preset the power supply to between 2.5V and 5.5V. c. Turn off the power supply. d. Connect positive power supply terminal to Vin. e. Connect power supply ground to EV board GND. f. Turn on the power supply and verify that the LEDS are lit. This application note contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice. No liability isassumed as a result of the use of this product. No rights under any patent accompany the sale of the product. PAM2841 EVB User Guide 5. EV Board BOM List Item Value Type Rating Description C1 10µF X5R/X7R,Ceramic/1210 10V Input coupling CAP C2 1µF X5R/X7R, Ceramic/0805 10V Vin coupling CAP C3 1µF X5R/X7R, Ceramic/1210 50V Output CAP C4 10nF X5R/X7R, Ceramic/0805 10V Comp CAP C5 1nF X5R/X7R, Ceramic/0805 10V Comp CAP R1 R2 R3 R4 L1 D1 Q1 White LED 910K 27K 10 2K 22µH 0805 0805 0805 0805 1210 1210 SOT23 3.2V(typ) 3.5V(max) at 20mA 5% 5% 1% 5% 1A 1A OVP Resistor OVP Resistor Iset Resistor Comp Resistor Inductor Schottky diode Nmosfet Vender and Part No. Murata GRM21R71C106B Murata GRM21R71C105B Murata GRM21R71C105B Murata GRM21R71C103B Murata GRM21R71C102B Murata LQH32CN220K NihonES11QS04 6. External Components Selection Input Capacitor (C1) and Output Capacitor (C3) (1) C1 Low ESR needed, 10uF, X5R/X7R ceramic recommended; (2) C3 Low ESR needed, 1µF, X5R/X7R (rating 50V) ceramic recommended. Coupling Capacitor (C2) and Comp Capacitors(C4,C5) (1) C2, Low ESR needed, 1µF, X5R/X7R ceramic recommended; (2) C4, Low ESR needed, 10nF, X5R/X7R ceramic recommended; (3) C5, Low ESR needed, 1nF, X5R/X7R ceramic recommended. Iset Resistor (R3) (1) R3 set the string’s LED current , Iled=0.2/R3; (2) R3, 10±1% recommended; OVP Resistors (R1, R2) (1) Vovp=V *(R1+R2)/R2; ov (2) R1, 910K±10% recommended; R2,27K±10% recommended; Inductor (L1) (1) Low DCR needed, 22µH (rating 1A) recommended. Schottky Diode (D1) (1) NihonES11QS06(1A, 60V) recommended. (2) B140 (1A, 40V) recommended. Mosfet (Q1) (1) 2N7002 recommended. This application note contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice. No liability isassumed as a result of the use of this product. No rights under any patent accompany the sale of the product. PAM2841 EVB User Guide 7. PCB Layout Guidelines Decoupling Capacitors (1) The capacitors (C2) need to place very close to the PAM2841’s pins. Grounding (1) The decoupling capacitors C2, C4 should each to be grounded to analog ground AGND; (2) The capacitors C1, C3, R2 and R3 should each be grounded to power ground PGND; (3) Connect the AGND and PGND islands by connecting the GND pins directly to the exposed backside pad. Make no other connections between these separate ground planes. Others (1) Connect L1, SW, D1, C3 with short and wide connections; (2) Place the OVP voltage setting-divider resistors (R1, R2) as close to the OV pin as possible. The divider’s center trace should be kept short; (3) Minimize the size of the SW node while keeping it wide and short. Keep the SW node away from the feedback node and ground; (4) Place the Iset resistors (R3) as close to the Iset pin as possible. 8. PCB Layout Example Top Layer Bottom Layer This application note contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice. No liability isassumed as a result of the use of this product. No rights under any patent accompany the sale of the product.