HT7938A Datasheet, PDF (2/13 Pages) Holtek Semiconductor Inc – Performance White LED Driver

Block Diagram
FB
O VP
O VP
P ro te c t
39V
R am p
1 .2 M H z
O SC
O TP
SR
R
Q
V IN
U V L O = 2 .1 V
SW
HT7938A
BG
Pin Assignment
Pin Description
Pin Name
I/O
SW
I
GND
―
FB
I
EN
I
VOP
O
VIN
I
Rev. 1.00
EN
GND
S O T 2 3 -6
V IN O V P E N
6
5
4
T o p V ie w
1
2
3
SW G N D FB
Desciption
Switching pin. Internal power MOSFET drain. Connected to inductor and diode.
Signal Ground.
Feedback pin. Reference voltage. The HT7938A feedback voltage is
200mV/300mV. Connect the sense resistor from FB to GND to set the LED
current. Calculate resistor value according to R_FB=200mV(300mV)/I_LED.
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.
Over voltage protection pin which is connected to the output.
Input supply pin. The input supply pin for the IC. Connect VIN to a supply
voltage between 2.6V~5.5V.
2
April 19, 2012