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SLVS441C – DECEMBER 2002 – REVISED MARCH 2007
CONSTANT CURRENT LED DRIVER
FEATURES
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Current Source With Overvoltage Protection
Input Voltage Range . . 1.8 V to 6 V
Internal 30 V Switch
Up to 85% Efficiency
Precise Brightness Control Using PWM Signal
or Analog Signal
Switching Frequency . . Up to 1 MHz
Internal Power MOSFET Switch . . 500 mA
Operates With Small Output Capacitors Down
to 100 nF
Disconnects LEDs During Shutdown
No Load Quiescent Current . . 38 µA Typ
Shutdown Current . . 0.1 µA Typ
Available in a Small 3 mm
×
3 mm QFN
Package
DESCRIPTION
The TPS61042 is a high frequency boost converter
with constant current output that drives white LEDs
or similar. The LED current is set with the external
sense resistor (R
S
) and is directly regulated by the
feedback pin (FB) that regulates the voltage across
the sense resistor R
S
to 252 mV (typ). To control
LED brightness, the LED current can be pulsed by
applying a PWM (pulse width modulated) signal with
a frequency range of 100 Hz to 50 kHz to the control
pin (CTRL). To allow higher flexibility, the device can
be configured where the brightness can be controlled
by an analog signal as well, as described in the
application information
section. To avoid possible
leakage currents through the LEDs during shutdown,
the control pin (CTRL) disables the device and
disconnects the LEDs from ground. For maximum
safety during operation, the output has integrated
overvoltage protection that prevents damage to the
device in case of a high impedance output (e.g.
faulty LED).
APPLICATIONS
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White LED Supply for Backlight/Sidelight
Displays
– PDA, Pocket PC, Smart Phones
– Handheld Devices
– Cellular Phones
L1
4.7 mH
D1
V
in
1.8 V to 6 V
3
VIN
SW
8
C
O†
100 nF
C
in
4.7 mF
5 CTRL OVP 7
6 GND LED 1
4 FB
R
S
2
Enable/PWM Brightness Control
100 Hz to 50 kHz
R
s
13 W
† Larger output capacitor values like 1 µF and larger, reduce the LED ripple current and improve line regulation.
Figure 1. Typical Application
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2002–2007, Texas Instruments Incorporated
TI [ TEXAS INSTRUMENTS ]
