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  Holtek Semiconductor Electronic Components Datasheet  

HT7938A Datasheet

High Current and Performance White LED Driver

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HT7938A
High Current and
Performance White LED Driver
Feature
• Efficiency up to 90% at VIN=4.0V, 5S2P,
ILED=20mA
• 1.2MHz fixed switching frequency
• Low standby current: 0.1mA (typ.) at VEN=0V
• Matches LED current
• Tiny inductor and capacitors
• EN pin dimming frequency up to 200kHz
• Up to 10 strings White-LED (LED VF(Max.)=3.5V)
• Tiny 6-lead SOT23-6 package
• Built in OVP, OCP, OTP, UVLO protection
Applications
• Cellular phones
• PDAs
• DSCs
• Handheld devices
• White LED display backlighting
General Description
The HT7938A is high efficiency boost converter with
constant current output for backlight applications in
handheld devices. Using a series connection of LEDs
provides constant identical LED currents resulting in
uniform brightness. The continuous LED current is
set using the device FB pin regulated voltage across
an external sense resistor, RFB, connected between this
pin and ground. The integrated open load protection
feature prevents device damage resulting from open
circuit load conditions. A low 300mV feedback
voltage minimises power losses in the current setting
resistor which provides enhanced efficiency. The
HT7938A has a dimming frequency of up to 200kHz,
which has excellent linear performance over this
dimming frequency range. The device switches at
rates of up to 1.2MHz to allow the use of extremely
small inductors and filter capacitors.
Selection Guide
Part No.
HT7938A
Package
SOT23-6
Note: Both lead free and green compound devices are available.
Marking
38A-3 (VFB=300mV)
Rev. 1.30
1 August 23, 2016


  Holtek Semiconductor Electronic Components Datasheet  

HT7938A Datasheet

High Current and Performance White LED Driver

No Preview Available !

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
RQ
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
VOP
VIN
I
O
I
Rev. 1.30
EN G ND
S O T 2 3 -6
V IN O V P
65
EN
4
3 8 A -3
T o p V ie w
1 23
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 300mV.
Connect the sense resistor from FB to GND to set the LED current. Calculate
resistor value according to RFB=300mV/ILED.
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 August 23, 2016


Part Number HT7938A
Description High Current and Performance White LED Driver
Maker Holtek Semiconductor
Total Page 12 Pages
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