Datasheet LT1943 (Analog Devices)

LT1943 High Current Quad Output Regulator for TFT LCD Panels
U FEATURES DESCRIPTIO
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4 Integrated Switches: 2.4A Buck, 2.6A Boost,
The LT®1943 quad output adjustable switching regulator
0.35A Boost, 0.35A Inverter (Guaranteed Minimum
provides power for large TFT LCD panels. The device,
Current Limit)
housed in a low profile 28 pin thermally enhanced TSSOP ■
Fixed Frequency, Low Noise Outputs
package, can generate a 3.3V or 5V logic supply along with ■
Soft-Start for all Outputs
the triple output supply required for the TFT LCD panel. Operating from an input range of 4.5V to 22V, a step-down ■
Externally Programmable VON Delay
regulator provides a low voltage output V ■ Integrated Schottky Diode for V LOGIC with up to ON Output 2A current. A high-power step-up converter, a lower- ■ PGOOD Pin for AVDD Output Disconnect power step-up converter and an inverting converter pro- ■ 4.5V to 22V Input Voltage Range vide the three independent output voltages AVDD, VON and ■ PanelProtectTM Circuitry Disables VON Upon Fault VOFF required by the LCD panel. A high-side PNP provides ■ Available in Thermally Enhanced 28-Lead TSSOP delayed turn-on of the V
U
ON signal and can handle up to 30mA. Protection circuitry ensures that V
APPLICATIO S
ON is disabled if any of the four outputs are more than 10% below the programmed voltage. ■ Large TFT-LCD Desktop Monitors ■ Flat Panel Televisions All switchers are synchronized to an internal 1.2MHz clock, allowing the use of low profile inductors and ce- , LTC and LT are registered trademarks of Linear Technology Corporation. PanelProtect is a trademark of Linear Technology Corporation. ramic capacitors throughout. A current mode architecture All other trademarks are the property of their respective owners. provides excellent transient response. For best flexibility, all outputs are adjustable. Soft-start is included in all four channels. A PGOOD pin can drive an optional PMOS pass device to provide output disconnect for the AVDD output.
U TYPICAL APPLICATIO
VIN, 8V TO 20V V 10µH OFF AVDD –5.5V 12.2V 50mA 500mA 0.47µF 10µF 1µF 33µH 10µH 2.2µF 88.7k 10µF 44.2k
Startup Waveforms
VIN SW3 SW4 SW2 10.0k RUN-SS NFB4 FB2 2V/DIV 0.015µF RUN-SS VLOGIC 10.0k 10pF 10µH 0.015µF 5V/DIV SS-234 0.047µF AV FB4 LT1943 C DD T 10V/DIV BIAS PGOOD PGOOD VON VOFF BOOST VON 35V 10V/DIV 30mA 0.22µF E3 SW1 274k V 4.7µH E3 16.2k FB3 20V/DIV VLOGIC V 3.3V FB1 GND 10.0k ON 2A 50V/DIV V SGND 10.0k C1 IIN(AVG) VC2 VC3 VC4 2.2µF 1A/DIV 22µF 5ms/DIV 18k 0.47 13k µF 6.8k 27k 100pF 100pF 100pF 100pF 2.2nF 2.2nF 680pF 2.2nF 1943 TA01
Quad Output TFT-LCD Power Supply
1943fa 1