PDF《X RP 7 6 1 8》

X XR RP P7

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8 8- -C Ch ha an nn ne el l C Co on ns st ta an nt t C Cu ur rr re en nt t L Li in ne ea ar r L LE ED D D Dr ri iv ve er r W Wi it th h S Sm ma ar rt t T Ta al lk kT TM M August

2011 Rev.

2.2.0 Exar Corporation www.exar.com

48720 Kato Road, Fremont CA 94538, USA Tel. +1

510 668-7000 C Fax. +1

510 668-7001 GENERAL DESCRIPTION The XRP7618 is an 8-channel, high voltage, constant-current sink LED driver capable of sinking up to 100mA current per channel. With outputs rated at 30V, the XRP7618 can control strings of multiple LEDs with better than ±1.5% channel to channel current matching. LED channel current is programmed via an external resistor within a 10mA to 100mA range. Dimming is supported up to 25kHz or through an analog signal. Featuring Exar'

s Smart TalkTM technology, when combined with a boost converter, XRP7618 maximizes the overall system efficiency by dynamically reporting the minimum LED voltage necessary to maintain current regulation mode. STANDARD CONFIGURATION The XRP7618EVB evaluation board is configured to operate under the following conditions and parameters: Input voltage range VCC:4.2V C 5.5V Input voltage range VLED:30V Number of LED strings:16 (2x8) LED current per string:

3 selectable pre-set levels 20mA-60mA-100mA Adj. Level 10mA to 100mA E EV VA AL LU UA AT TI IO ON N B BO OA AR RD D M MA AN NU UA AL L FEATURES ?

8 Constant-Current Channels ? Adjustable up to 100mA per Channel ? Channel Paralleling for higher Current ? ±1.5% Current Matching Accuracy ? Up to 30V LED Channel Voltage Range ? 5V Biasing Voltage and Control ? Smart TalkTM Power Optimization ? Parallel Operations Support ? PWM and Analog Dimming ? UVLO, Open LED &

Over Temperature protection ? 20-pin TSSOP (EP) Package EVALUATION BOARD SCHEMATICS Fig. 1: XRP7618 Evaluation Board Schematics X XR RP P7

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2011 Exar Corporation 2/7 Rev. 2.2.0 PIN ASSIGNMENT Fig. 2: XRP7618 Pin Assignment PIN DESCRIPTION Name Pin Number Description CHx 1, 2, 3, 4, 7, 8, 9,

10 CH1 to CH8 pins Connect an LED between each pin and LED supply rail voltage (VLED). Current value is controlled by RSET. Connect unused channel(s) to GND. NC

12 Not Connected PWM

11 PWM pin This must be held HIGH to enable the output drivers. It can be used for PWM dimming up to 25kHz. If not used, connect to VCC. FBX

13 FBX input pin Used in parallel configuration as an interface terminal by connecting it to FB pin of the next XRP7618. If not used, leave it unconnected. ISET

14 ISET pin Connect resistor RSET from this pin to ground to set LED channel current as per ICHANNEL=1.194x400/RSET FB

15 FB pin Samples the LED cathode voltage on each channel and outputs the lowest voltage to the step-up converter. SDB

16 SDB output pin SDB signal is synchronous with the PWM signal during PWM Dimming. SDB pin outputs low logic to the step-up converter under conditions such as shutdown or when all channels are inactive. SDBX

17 SDBX input pin Used in parallel configuration as an interface terminal by connecting it to SDB pin of the next XRP7618. If not used, connect it to GND. AGND

18 Ground pin VCC

19 Input Voltage pin Must be closely decoupled to GND pin with a 0.1μF ceramic capacitor. EN

20 Enable pin This pin must be held HIGH to enable the XRP7618. PGND 5,

6 Ground pin EP Exposed Pad Exposed Pad Connect to ground ORDERING INFORMATION Refer to XRP7618'