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LED Driver. HT7938A Datasheet

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LED Driver. HT7938A Datasheet






HT7938A Driver. Datasheet pdf. Equivalent




HT7938A Driver. Datasheet pdf. Equivalent





Part

HT7938A

Description

High Current and Performance White LED Driver



Feature


HT7938A High Current and Performance Whi te 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.) a t VEN=0V • Matches LED current • Tiny inductor and capacitors • EN pi n dimming frequency up to 200kHz • U p to 10 strings White-LED (LED VF(Max.) =3.5V) • Tiny 6-lead SOT23-6 pa.
Manufacture

Holtek Semiconductor

Datasheet
Download HT7938A Datasheet


Holtek Semiconductor HT7938A

HT7938A; ckage • Built in OVP, OCP, OTP, UVLO protection Applications • Cellular p hones • PDAs • DSCs • Handheld devices • White LED display backlig hting 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 c onstant identical LED currents.


Holtek Semiconductor HT7938A

resulting in uniform brightness. The co ntinuous LED current is set using the d evice FB pin regulated voltage across a n external sense resistor, RFB, connect ed between this pin and ground. The int egrated open load protection feature .


Holtek Semiconductor HT7938A

.

Part

HT7938A

Description

High Current and Performance White LED Driver



Feature


HT7938A High Current and Performance Whi te 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.) a t VEN=0V • Matches LED current • Tiny inductor and capacitors • EN pi n dimming frequency up to 200kHz • U p to 10 strings White-LED (LED VF(Max.) =3.5V) • Tiny 6-lead SOT23-6 pa.
Manufacture

Holtek Semiconductor

Datasheet
Download HT7938A Datasheet




 HT7938A
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




 HT7938A
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




 HT7938A
HT7938A
Absolute Maximum Ratings
Input Voltage ........................................................ 6.0V
SW Voltage ........................................................... 46V
FB Voltage ........................................................... 6.0V
EN ........................................................................ 6.0V
OVP Voltage ......................................................... 46V
Operating Temperature Range ........... -40°C to +85°C
Storage Temperature Range ............. -55°C to +150°C
Maximum Junction Temperature ...................... 150°C
Note: These are stress ratings only. Stresses exceeding the range specified under Absolute Maximum Ratings may
cause substantial damage to the device. Functional operation of this device at other conditions beyond those
listed in the specification is not implied and prolonged exposure to extreme conditions may affect device
reliability.
Electrical Characteristics
VIN= 3.6V, L=22mH, CIN=1mF, COUT=4.7mF, ILED=20mA, Ta=25°C, unless otherwise specified (Note 1)
Symbol
Parameter
Test Conditions
Min. Typ. Max. Unit
Input Supply Voltage and Current
VIN Input Voltage
UVLO Under Voltage Lockout
― 2.6 ― 5.5 V
―
1.8 2.1 2.4
V
IIN Supply Current
Error Amplifier
Switching
VEN=0
― 1.0 5.0 mA
― 0.1 1.0 ÎĵA
VFB Feedback Voltage
VLine Line Regulation
Power Switch
For 38A-3 Marking
VIN=3.0~4.3V, ILED=20mA
285 300 315 mV
― 1.0 ―
%
fOSC Switching Frequency
DC Maximum Duty Cycle
Measured at SW Pin
0.8 1.2 1.6 MHz
92 95 ― %
RDS(ON)
ISW(OFF)
Enable
SW ON Resistance
Switch Leakage Current
―
― 0.7 ―
Îİ
― ― 0.1 1.0 ÎĵA
VIH EN Voltage High
VIL EN Voltage Low
fEN Dimming Clock Rate
OVP and OCP
―
―
Duty= 5%~100%
2.0 ― ― V
― ― 0.8 V
0.1 ― 200 kHz
VOVP OVP Threshold
No Load
IOCP N-channel MOSFET Current limit
Thermal Shutdown
―
36 39 42
― 1000 ―
V
mA
Thermal Shutdown Threshold
tSHUT
Thermal Shutdown Hysteresis
―
―
― 150 ―
― 25 ―
°C
°C
Note 1. Specifications are production tested at Ta=25 degree. Specifications over -40°C to 85°C degree operating
temperature range are assured by design, characterization.
Rev. 1.30
3 August 23, 2016



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