TPS61042 Datasheet, PDF (1/22 Pages) Texas Instruments – CONSTANT CURRENT LED DRIVER

www.ti.com
TPS61042
SLVS441B — DECEMBER 2002 — REVISED JANUARY 2003
CONSTANT CURRENT LED DRIVER
FEATURES
• ^{Current Source With Overvoltage Protection}
••••
Input Voltage Range . . 1.8 V to 6.0 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
• 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
C_in
4.7 mF
3
8
VIN SW
5 _{CTRL OVP} 7
6 _{GND LED} 1
4 _FB
R_S ²
C_O†
100 nF
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 Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
Copyright © 2003, Texas Instruments Incorporated