Rev. 1.00

2

April 19, 2012

HT7938A

Block Diagram

S

R

R

Q

1. 2M Hz

OS C

UV LO = 2. 1V

OT P

VI N

GN D

FB

Ra mp

OV P

OV P

Pr ot ec t

39 V

BG

SW

EN

Pin Assignment

SW

GN D

To p Vi ew

VI NE N

FB

12

3

4

6

5

OV P

SO T 23- 6

Pin Description

Pin Name

I/O

Desciption

SW

I

Switching pin. Internal power MOSFET drain. Connected to inductor and diode.

GND

―

Signal Ground.

FB

I

Feedback pin. Reference voltage. The HT7938A feedback voltage is

200mV/300mV. Connect the sense resistor from FB to GND to set the LED

EN

I

Shutdown & Dimming control input. Don't allow this pin to float.

When dimming control input high to low level period more than 20ms and have

no other dimming signal, the device is entered shutdown mode.

VOP

O

Over voltage protection pin which is connected to the output.

VIN

I

Input supply pin. The input supply pin for the IC. Connect VIN to a supply

voltage between 2.6V~5.5V.