AMC7140 AMC7140 EVM User Guide Circuit Scheme: VLED＋ Jumper VIN = 5V~50V Switch LED＋ ON CIN + OE OFF VDD VLED AMC7140 ISET GND LED－ OUT Light Bar VR R VF >880Ω GND Picture Output Port VLED+ Jumper Input Port Slide Switch Variable Resistor: VR Copyright © 2006, ADDtek Corp. http://www.addmtek.com DA026-2 － November 16, 2006 1 AMC7140 Bill of Material C.R No. Q’TY Description PCB 1 PCB-AMC7140 (version: 060912) IC 1 AMC7140DL CIN 1 E. C. Cap. 10uF / 63V R 1 R= VR 1 Variable Resistor / 20KΩ Switch 1 3P, 180° Slide Switch I OUT , MAX 1.2V ; I SET = I SET 500 Description 【 1】 The recommended range for input voltage V IN is: V LED +0.35V≦ V IN ≦ V LED +1.5V. Where, V LED is the total forward voltage drops of the LED string (V LED =nxV F , where, V F is the forward voltage of one LED, and n is the number of LEDs in the string). Too large input voltage will result in too large voltage drop between OUT pin and GND pin. In such condition, additional heat sink is necessary and appropriate size of copper foil on EVM is required. 【 2】 The slide switch is used to turn ON or OFF the output stage of the chip. 【 3】 The resistor R is used to set the maximum allowable LED driving current. The value of R is calculated by the following formula: I SET = I OUT , MAX 500 , R= VSET 1.2V = I SET I SET 【 4】 The dimming function can be accomplished by variable resistor VR. The current ratio between I OUT and I SET is 500. Reference PCB Layout Top Layer Copyright © 2006, ADDtek Corp. http://www.addmtek.com Bottom Layer DA026-2 － November 16, 2006 2