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Linear Technology Electronic Components Datasheet

LT1943 Datasheet

High Current Quad Output Regulator

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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
PanelProtectTM 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 VLOGIC 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 AVDD, VON and
VOFF required by the LCD panel. A high-side PNP provides
delayed turn-on of the VON signal and can handle up to
30mA. Protection circuitry ensures that VON 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 AVDD output.
TYPICAL APPLICATIO
VOFF
–5.5V
50mA
VIN, 8V TO 20V
2.2µF 44.2k
0.47µF
10µF
10µH
33µH
VLOGIC
3.3V
2A
10.0k
16.2k
10.0k
22µF
SW4
NFB4
10pF 10µH
0.22µF
4.7µH
FB4
BIAS
BOOST
SW1
FB1
VC1
VIN SW3 SW2
FB2
RUN-SS
LT1943
SS-234
CT
PGOOD
VON
E3
FB3
GND
SGND
VC2 VC3
VC4
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
AVDD
12.2V
500mA
10µF
VON
35V
30mA
0.47µF
Quad Output TFT-LCD Power Supply
1943 TA01
RUN-SS
2V/DIV
VLOGIC
5V/DIV
AVDD
10V/DIV
VOFF
10V/DIV
VE3
20V/DIV
VON
50V/DIV
IIN(AVG)
1A/DIV
Startup Waveforms
5ms/DIV
1943fa
1


Linear Technology Electronic Components Datasheet

LT1943 Datasheet

High Current Quad Output Regulator

No Preview Available !

LT1943
ABSOLUTE AXI U RATI GS
(Note 1)
VIN Voltage .............................................................. 25V
BOOST Voltage ........................................................ 36V
BOOST Voltage Above SW1 ..................................... 25V
BIAS Pin Voltage ..................................................... 18V
SW2, SW4 Pin Voltages .......................................... 40V
SW3 Voltage ............................................................ 40V
FB1, FB2, FB3, FB4 Voltages ...................................... 4V
NFB4 Voltage ................................................ +6V, –0.6V
VC1, VC2, VC3, VC4 Pin Voltages .............................. 6V
RUN-SS, SS-234 Pin Voltages ................................... 6V
PGOOD Pin Voltage ................................................. 36V
E3 Pin Voltage ......................................................... 38V
VON Voltage ............................................................. 38V
CT Pin Voltage ........................................................... 6V
Junction Temperature ........................................... 125°C
Operating Temperature Range (Note 2) ...–40°C to 85°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GND 1
28 SW2
VC1 2
27 SW2
VC2 3
FB1 4
26 VON
25 CT
FB2 5
24 E3
FB3 6
23 PGOOD
NFB4 7 29 22 BIAS
FB4 8
21 SW3
VC3 9
20 GND
VC4 10
19 SW4
SGND 11
18 RUN-SS
BOOST 12
17 SS-234
SW1 13
16 VIN
SW1 14
15 VIN
FE PACKAGE
28-LEAD PLASTIC TSSOP
EXPOSED PAD (PIN 29) IS GROUND
(MUST BE SOLDERED TO PCB)
TJMAX = 125°C, θJA = 25°C/W, θJC = 7.5°C/W
ORDER PART
NUMBER
LT1943EFE
FE PART MARKING
1943E
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, RUN-SS, SS-234 = 2.5V unless otherwise noted.
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
Quiescent Current
RUN-SS, SS-234 Pin Current
RUN-SS, SS-234 Threshold
BIAS Pin Voltage to Begin SS-234 Charge
BIAS Pin Current
FB Threshold Offset to Begin CT Charge
CT Pin Current Source
CT Threshold to Power VON
VON Switch Drop
Maximum VON Current
PGOOD Threshold Offset
PGOOD Sink Current
PGOOD Pin Leakage
Master Oscillator Frequency
Foldback Switching Frequency
Frequency Shift Threshold on FB
CONDITIONS
Not Switching
RUN-SS = SS-234 = 0V
RUN-SS, SS-234 = 0.4V
BIAS = 3.1V, All Switches Off
(Note 3)
All FB Pins = 1.5V
All FB Pins = 1.5V
VON Current = 30mA
VE3 = 30V
VPGOOD = 36V
All FB Pins = 0V
200kHz
MIN TYP MAX UNITS
4.5 V
22 V
10 14
35 45
mA
µA
1.7 µA
0.8 V
2.4
2.8 3.15
V
10.5 15
mA
90 125 160
mV
16 20 25
µA
1.0 1.1 1.2
V
180 240
mV
30
60
mA
90 125 160
mV
200 µA
1 µA
1.1
1.0
1.2 1.35
1.46
MHz
MHz
250 kHz
0.5 V
1943fa
2


Part Number LT1943
Description High Current Quad Output Regulator
Maker Linear
PDF Download

LT1943 Datasheet PDF






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