Rev. 1.00

3

April 13, 2012

HT7945

Pin Assignment

LED7

LED8

1

6

7

18

12

19

13

24

Exposed Pad

EN

DIM

LED1

ISET

AGND1

COMP

LX1

LX2

PGND2

TOP VIEW

PGND3

HT7945

24 QFN-A

4mm x 4mm

Pin Description

PIN

Name

Description

1

EN

Enable Input.

When low, the device is powered down. If tied high or left open, the device is active.

2, 10

AGND1, AGND2 Analog ground

3

COMP

Error Amplifier Output.

A simple RC series is connected between this pin and the analog ground for boost

regulator loop compensation.

4

DIM

Dimming Input.

LED backlight strings PWM control pin.

5

ISET

Full Scale LED Current Adjustment Pin.

Selection implemented by connection a resistor beteen this pin and the analog ground.

6~9,

11~14

LED1 ~

LED8

LED current sink.

Internal regulator open-drain outputs Can sink up to 30mA. If unused, the pins should

be left open.

15, 16

LX2, LX1

Switching Node.

Internal Power MOSFET drain output. Inductor and Schottky diode are connected to

these pins.

17~19

PGND1 ~

PGND3

Power Ground.

Power MOSFET return path.

20

IN

Input Voltage.

Input voltage range from 4.5V to 26V. Bypass IN to analog ground directly at the pin

with 0.1uF or greater ceramic capacitor.

21

VCC5

Internal 5.2V LDO Output.

Bypass to analog ground with a 10uF or greater ceramic capacitor. If VIN is less than

or equal to 6.0V, connect VCC5 to IN to disable the internal LDO.

22

AVDD

Power MOSFET Gate Drive Supply.

Bypass AVDD to analog ground with a ceramic capacitor of 10uF or greater.

23

OVP

Over Voltage Protection.

Used to set the desired OVP threshold using an external resistor divider. The detector

24

OSC

Oscillator Frequency Selection.

Connect OSC to VCC5 to set the oscillator frequency to 1MHz. Connect OSC to analog

ground to set the frequency to 500kHz.

—

E.P.

Exposed Pad.

Connect to GND plane of the PCB.