LT1943 Datasheet, PDF (1/12 Pages) Linear Technology – High Current Quad Output Regulator for TFT LCD Panels

Final Electrical Specifications
LT1943
High Current Quad Output
Regulator for TFT LCD Panels
FEATURES
DESCRIPTIO
September 2003
s _{4 Integrated Switches: 2.4A Buck, 2.6A Boost,}
0.35A Boost, 0.35A Inverter (Guaranteed Minimum
Current Limit)
s _{Fixed Frequency, Low Noise Outputs}
s _{Soft Start for all Outputs}
s _{Externally Programmable VON Delay}
s _{Integrated Schottky Diode for VON Output}
s _{PGOOD Pin for AVDD Output Disconnect}
s _{4.5V to 22V Input Voltage Range}
s _PanelProtect^TM _{Circuitry Disables VON Upon Fault}
s _{Thermally Enhanced 28-Lead TSSOP}
U
APPLICATIO S
s _{Large TFT-LCD Desktop Monitor Displays}
s _{Flat Panel Televisions}
, LTC and LT are registered trademarks of Linear Technology Corporation.
PannelProtect is a trademark of Linear Technology Corporation.
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 V_ON is disabled if any
of the four outputs are more than 10% below normal
voltage.
All switchers are synchronized to the 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
–10V
50mA
V_LOGIC
3.3V
2A
ZHCS400
V_IN, 8V TO 20V
10µH
2.2µF
80.6k
0.47µF
16V
ZHCS400
10µF
33µH
SW4
V_IN SW3 _SW2
NFB4
FB2
10.0k
10pF 10µH
LT1943
RUN-SS
SS-234
FB4
C_T
BIAS
PGOOD
CMDSH-3
0.22µF
10V
16.2k
4.7µH
B230A
10.0k
22µF
BOOST
SW1
FB1
VC1
VC2
V_ON
E3
FB3
GND
SGND
VC3 VC4
B240A
1µF
25V ^10µH
95.3k
10.0k
0.015µF
0.015µF
0.047µF
PGOOD
232k
10.0k
2.2µF
27.4k
100pF
2.2nF
100pF
2.2nF
6.81k
47.5k
100pF
680pF
13k
100pF
2.2nF
AV_DD
13V
500mA
10µF
V_ON
30V
30mA
0.47µF
1943 F01
Figure 1. 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
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
1943i
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