ADP8140ACPZ-1-R7 datasheet(11/23 Pages) AD

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Data Sheet

ADP8140

Rev. B | Page 11 of 23

THEORY OF OPERATION

The ADP8140 provides high current control of up to four LED

channels. Each driver can sink up to 500 mA. One external

resistor programs the sink current for all four channels. The

device features a feedback output that controls an external

power supply for optimal efficiency. The ADP8140 also protects

the LEDs, power supply, and itself against thermal events, short

circuits, and LED open circuits. Multiple ADP8140 ICs are

easily connected in parallel to drive additional LED strings or

higher current LEDs.

START-UP SEQUENCE

To start the ADP8140, VIN must be applied in excess of the

UVLO threshold and the EN pin must be high. However, even

with EN low, the REG pin produces a constant 3.0 V (typical)

on its output. REG can be used as a low current supply, as

needed. In this operation, with EN low, the ADP8140 consumes

no more than 200 μA (typical). A 400 kΩ (typical) resistor from

EN to GND ensures that the ADP8140 is shut down in the

event of an open connection on the EN pin.

When EN also goes high, the power stage starts up and the

current sinks are enabled. There is an approximate 8 ms delay

after EN goes high. When the sinks are enabled, the

FAULTE

is released and the COMP and FB_OUT pins begin their

normal regulation. When EN goes low, the SINKx pins are left

on for another 100 μs to discharge any voltage from the power

stage output. The device then enters low current consumption

operation.

Figure 20. Detailed Block Diagram

CIN

SINK1

SINK2

SINK3

SINK4

ID1

ID2

ID4

ISET

GND

(EXPOSED PAD)

VO_SNS

1.2V

NOISE FILTER

ID3

VOUT_OVP

SHUTDOWN

VOUT

SINK

CONTROL

16-LEAD EXPOSED PAD THERMALLY ENHANCED PACKAGE

SINK EN

8V/15V

3.0V TO 30V

SCALE

NTC

VOUT

MIN

REDUCE CURRENT

WHEN DIE TEMP

> 135°C

FB_OUT

FAULT

REG

VIN

REG

3.0V

VT < MIN

VREG_OK

MIN

CH_OVP

5.7V

MAX

VEA(REF)

COMP

TSD

RESET

ALL FAULTS

1.2V

10 µs

NOISE

FILTER

400kΩ

UVLO

ISET SHORT

DIM

MODE

SINKx < 550mV?

IF SO, REMOVE

FROM FB LOOP

MIN

AND

MAX

DIM

CONTROL

DIE TEMP

SENSE

10 µs

SINKx < 75mV?

IF SO, REMOVE

FROM FB LOOP

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