ZLED7001 Datasheet

© 2016 Integrated Device Technology, Inc.

6

April 20, 2016

Bandgap

Blanking

480ns

RS

POR

UVLO

n LED

L1

R2

NTC

5

6

D1

RCS

CLED

Q1

VS

CIN

C1

R1

8 to 450 VDC

2

3

1

RIN

CS

LD

VREF

VIN

PWMD

GATE

GND

4

7

COFF

TOFF

ZLED7001

Timing

Circuit

7.1V Clamp

R

R

R

0.24V

0.05V

+

+

–

–

+

–

0.24V

Driver

R

S

Q

CMP1

CMP2

CMP3

8

vdda

vdda

vddd

Voltage

Regulator

REN

2

Circuit Description

The ZLED7001 is a peak current-mode-control LED driver IC that operates in constant off-time mode, enabling

proper LED current control without additional loop compensation or high-side current sensing. The ZLED7001

supports both linear and PWM control of the LED current. Only a few external components are needed for typical

applications. It is well-suited for buck LED driver applications.

2.1.

ZLED7001 Block Diagram

2.2.

Application Signal Flow

A capacitor between the TOFF pin and ground determines the internal timer’s off-time. The timer pulses set flip-flop

in the ZLED7001, turning on the GATE pin driver, which is connected to the Q1 external MOSFET. When Q1

turns on, a ramp current flows through the LED(s), the L1 external inductor, and the external sense resistor RCS.

This results in a ramp voltage applied at the CS pin, which the ZLED7001’s two internal comparators continually

compare to the voltage at its LD pin and its internal 240mV reference. If either comparator goes high and the

blanking time is expired (see Table 1.3), the flip-flop is reset, causing the GATE pin output to go low, shutting off

the current through the LED(s).

The peak current control scheme with constant off-time can easily operate at duty cycles higher than 0.5 and also

gives inherent input voltage rejection, making the LED current almost insensitive to input voltage variations.