Programmable, Four-String HB LED Driver with

Output-Voltage Optimization and Fault Detection

8

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Pin Description

PIN

NAME

FUNCTION

1

PGND

Power Ground

2, 3

GND

Analog Ground

4

RTCT

RTCT and a capacitor C33, from RTCT to GND set the oscillator frequency. See the Oscillator section to

calculate RT and CT component values.

5

SYNC/EN

Synchronization and Enable Input. There are three operating modes:

SYNC/EN = LOW: Low current shutdown mode with all circuits shut down except shunt regulator.

SYNC/EN = HIGH: All circuits active with oscillator frequency set by RTCT network.

SYNC/EN = CLOCKED: All circuits active with oscillator frequency set by SYNC clock input. Conversion

cycles initiate on the rising edge of external clock input. The frequency programmed by R19/C33 must be

10% lower than the input SYNC/EN signal frequency.

6

CSS

Soft-Start Timing Capacitor Connection. Connect a capacitor from CSS to GND to program the required soft-

start time for the switching regulator output voltage to reach regulation. See the Soft-Start (CSS) section to

7

COMP

Switching Regulator Compensation Component Connection. Connect the compensation network between

COMP and FB.

8FB

Switching Regulator Feedback Input. Connect FB to the center of a resistor-divider connected between the

switching regulator output and GND to set the output voltage. FB is regulated to a voltage set by an internal

register. See the Setting Output Voltage section for calculating resistor values.

9

OVP

Switching Regulator Overvoltage Input. Connect OVP to the center of a resistor-divider connected between the

switching regulator output and GND. For normal operation, configure the resistor-divider so that the voltage at

this pin does not exceed 1.25V. If operation under load dump conditions is also required, configure the resistor-

divider so that the voltage at OVP is less than 1.25V.

10

RSC

Slope Compensation Resistor and PWM Comparator Input Connection. Connect a resistor, R17, from RSC to

the switching current-sense resistor to set the amount of the compensation ramp. See the Slope Compensation

(RSC) section for calculating the value.

11

SDA

12

SCL

13

DIM1

LED String 1 Logic-Level PWM Dimming Input. A high logic level on DIM1 enables the current sink to operate at

the maximum current as determined by its sense resistor and internal register value. A low logic level disables

the current source.

14

DIM2

LED String 2 Logic-Level PWM Dimming Input. A high logic level on DIM2 enables the current sink to operate at

the maximum current as determined by its sense resistor and internal register value. A low logic level disables

the current source.

15

DIM3

LED String 3 Logic-Level PWM Dimming Input. A high logic level on DIM3 enables the current sink to operate at

the maximum current as determined by its sense resistor and internal register value. A low logic level disables

the current source.

16

DIM4

LED String 4 Logic-Level PWM Dimming Input. A high logic level on DIM4 enables the current sink to operate at

the maximum current as determined by its sense resistor and internal register value. A low logic level disables

the current source.

17

CS1

LED String 1 Current-Sense Input. CS1 is regulated to a value set by an internal register. The regulation voltage

can be set between 97mV and 316mV.