LT1943_1 Datasheet, PDF (1/20 Pages) Linear Technology – High Current Quad Output Regulator for TFT LCD Panels

LT1943
High Current Quad Output
Regulator for TFT LCD Panels
FEATURES
■ _{4 Integrated Switches: 2.4A Buck, 2.6A Boost,}
0.35A Boost, 0.35A Inverter (Guaranteed Minimum
Current Limit)
■ _{Fixed Frequency, Low Noise Outputs}
■ _{Soft-Start for all Outputs}
■ _{Externally Programmable VON Delay}
■ _{Integrated Schottky Diode for VON Output}
■ _{PGOOD Pin for AVDD Output Disconnect}
■ _{4.5V to 22V Input Voltage Range}
■ _PanelProtect^TM _{Circuitry Disables VON Upon Fault}
■ _{Available in Thermally Enhanced 28-Lead TSSOP}
U
APPLICATIO S
■ _{Large TFT-LCD Desktop Monitors}
■ _{Flat Panel Televisions}
, LTC and LT are registered trademarks of Linear Technology Corporation.
PanelProtect is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
DESCRIPTIO
The LT^®1943 quad output adjustable switching regulator
provides power for large TFT LCD panels. The device,
housed in a low profile 28 pin thermally enhanced TSSOP
package, can generate a 3.3V or 5V logic supply along with
the triple output supply required for the TFT LCD panel.
Operating from an input range of 4.5V to 22V, a step-down
regulator provides a low voltage output V_LOGIC with up to
2A current. A high-power step-up converter, a lower-
power step-up converter and an inverting converter pro-
vide the three independent output voltages AV_DD, V_ON and
V_OFF required by the LCD panel. A high-side PNP provides
delayed turn-on of the V_ON signal and can handle up to
30mA. Protection circuitry ensures that V_ON is disabled if
any of the four outputs are more than 10% below the
programmed voltage.
All switchers are synchronized to an internal 1.2MHz
clock, allowing the use of low profile inductors and ce-
ramic capacitors throughout. A current mode architecture
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 AV_DD output.
TYPICAL APPLICATIO
V_OFF
–5.5V
50mA
V_IN, 8V TO 20V
2.2µF _44.2k
0.47µF
10µF
10µH
33µH
V_LOGIC
3.3V
2A
10.0k
16.2k
10.0k
22µF
SW4
NFB4
10pF 10µH
0.22µF
4.7µH
FB4
BIAS
BOOST
SW1
FB1
V_C1
V_IN SW3 _SW2
FB2
RUN-SS
LT1943
SS-234
C_T
PGOOD
V_ON
E3
FB3
GND
SGND
V_C2 V_C3
V_C4
1µF
10µH
88.7k
10.0k
0.015µF
0.015µF
0.047µF
PGOOD
274k
10.0k
2.2µF
18k
100pF
2.2nF
100pF
2.2nF
6.8k 27k
100pF
680pF
13k
100pF
2.2nF
AV_DD
12.2V
500mA
10µF
V_ON
35V
30mA
0.47µF
1943 TA01
Quad Output TFT-LCD Power Supply
RUN-SS
2V/DIV
V_LOGIC
5V/DIV
AV_DD
10V/DIV
V_OFF
10V/DIV
V_E3
20V/DIV
V_ON
50V/DIV
I_IN(AVG)
1A/DIV
Startup Waveforms
5ms/DIV
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