LT1947 Datasheet, PDF (1/8 Pages) Linear Technology – Adjustable Output TFT-LCD Triple Switching Regulator

LT1947
Adjustable Output TFT-LCD
Triple Switching Regulator
FEATURES
s _{Complete Solution Under 1.2mm}
s _{Develops Three Outputs from a 3.3V or 5V Supply}
s _{Externally Programmable VON Delay}
s _{Fixed Frequency Low Noise Outputs}
s _{All Ceramic Capacitors}
s _{3MHz Switching Frequency}
s _{Fast Transient Response}
s _{Few External Components Required}
s _{2.7V to 8V Input Range}
s _{Adjustable AVDD and VON Voltages}
s _{Tiny 10-Lead MSOP Package}
U
APPLICATIO S
s _{TFT-LCD Notebook Display Panels}
s _{TFT-LCD Desktop Monitor Display Panels}
s _{Digital Cameras}
s _{Handheld Computers}
DESCRIPTIO
The LT^®1947 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. The second regulator’s output is also adjustable up
to 30V and can deliver 10mA for positive bias. A simple
level-shift charge pump off the main switch node gener-
ates the negative bias voltage. An external capacitor sets
the delay time from AV_DD’s final value to the rising edge at
the V_ON pin. The 3MHz switching frequency allows the use
of tiny low profile chip inductors and capacitors through-
out, providing a low noise, low cost total solution with all
components under 1.2mm in height. The device operates
from an input range of 2.7V to 8V and is available in a
10-lead MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
V_IN
C1
2.2µF
CERAMIC
SHUTDOWN
D3
D4
L1
3.3µH
C6
0.68µF
L2
4.7µH
V_IN
SW2
D1
SW1
FB1
D2
C3
220nF
V_O2 LT1947
R3
182k
FB2
V_ON
R4 _{SHDN CT GND}
10k
C5
10nF
R1
53.6k
R2
10k
V_OFF
–8V
C4 ^10mA
0.68µF
CERAMIC
AV_DD
8V
200mA
C2
3.3µF
CERAMIC
×2
V_ON
24V
10mA
C1: TAIYO YUDEN LMK316BJ225MD
C2: TAIYO YUDEN LMK325BJ335MD ×2
C3: AVX 0.22µF 25V X7R
C4, C6: TAIYO YUDEN LMK107BJ684MA
D1: MBRM120LT3
D2: CMDSH-3
1947 F01
D3, D4: BAT54S DUAL DIODE
L1: SUMIDA CLQ4D103R3
L2: TAIYO YUDEN LB2012B4R7M
Figure 1. 3.3V Powered TFT-LCD Bias Generator
V_SHDN
5V/DIV
V_ON
20V/DIV
AV_DD
10V/DIV
V_OFF
10V/DIV
Start-Up Waveforms
2ms/DIV
1947 TA01.tif
1947f
1