LT1948 Datasheet, PDF (1/4 Pages) Linear Integrated Systems – DC/DC Converter for TFT-LCD Panels

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FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
FEATURES
I _{Complete Solution Under 1.2mm}
I _{Develops Three Outputs from a 3.3V or 5V Supply}
I _{Externally Programmable VON Delay}
I _{Fixed Frequency Low Noise Outputs}
I _{All Ceramic Capacitors}
I _{Operates at 3MHz Switching Frequency}
I _{Fast Transient Response}
I _{Few External Components Required}
I _{2.6V to 6V Input Range}
I _{Tiny 8-Lead MSOP Package}
U
APPLICATIO S
I _{TFT-LCD Notebook Display Panels}
I _{TFT-LCD Desktop Monitor Display Panels}
I _{Digital Cameras}
I _{Handheld Computers}
Final Electrical Specifications
LT1948
DC/DC Converter for
TFT-LCD Panels
August 2000
DESCRIPTIO
The LT^®1948 is a highly integrated multiple output DC/DC
converter designed for use in TFT-LCD panels. The device
contains two independent switching regulators: the main
regulator has an adjustable output voltage with an internal
1.1A switch that can generate a boosted voltage as high as
30V while the second regulator generates 23V at up to
10mA for positive bias. A simple level-shift charge pump
off the main switch node generates the negative bias
voltage. An external capacitor sets the delay time from
AV_DD reaching final value to 23V appearing at the V_ON pin.
The 3MHz switching frequency allows the use of tiny low
profile chip inductors and capacitors throughout, provid-
ing a low noise, low cost total solution with all components
under 1.25mm in height. The device operates from an
input range of 2.6V to 6V and is available in an 8-lead
MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
D3A ^BAT54S D3B
V_IN
2.5V TO
6V
C1
2.2µF
L3
2.2µH
D2
CMDSH-3
C3
0.22µF
L1, 2.2µH
L2, 2.2µH
C5
C4
1µF
0.22µF
D1
MBRM120
V_IN
SW2
LT1948
VO2
C_T
C6
22nF
SW1
FB1
V_ON
GND
R1
53.6k
R2
10k
C1, C2: TAIYO YUDEN LMK212BJ225
C3: TAIYO YUDEN TMK316BJ224
C4: TAIYO YUDEN EMK212BJ224
C5: TAIYO YUDEN LMK212BJ105
L1–L3: TAIYO YUDEN LB2012-2R2
V_OFF
–8V
15mA
AV_DD
8V
260mA
C2
2.2µF
V_ON
23V
10mA
1948 F01
Figure 1. 3.3V Powered TFT-LCD Bias Generator
V_IN
5V/DIV
V_ON
20V/DIV
AV_DD
10V/DIV
V_OFF
10V/DIV
Start-Up Waveforms
2ms/DIV
1948 TA01a
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.
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