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Linear Technology Electronic Components Datasheet

LT1947 Datasheet

Adjustable Output TFT-LCD Triple Switching Regulator

No Preview Available !

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 AVDD’s final value to the rising edge at
the VON 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
VIN
C1
2.2µF
CERAMIC
SHUTDOWN
D3 D4
L1
3.3µH
C6
0.68µF
L2
4.7µH
VIN
SW2
SW1
FB1
D1
D2
C3
220nF
R3
182k
R4
10k
VO2 LT1947
FB2 VON
SHDN CT GND
C5
10nF
R1
53.6k
R2
10k
VOFF
–8V
C4 10mA
0.68µF
CERAMIC
AVDD
8V
200mA
C2
3.3µF
CERAMIC
×2
VON
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
VSHDN
5V/DIV
VON
20V/DIV
AVDD
10V/DIV
VOFF
10V/DIV
Start-Up Waveforms
2ms/DIV
1947 TA01.tif
1947f
1


Linear Technology Electronic Components Datasheet

LT1947 Datasheet

Adjustable Output TFT-LCD Triple Switching Regulator

No Preview Available !

LT1947
ABSOLUTE AXI U RATI GS
(Note 1)
VIN Voltage ................................................................ 8V
CT Voltage.................................................................. 6V
SW1, SW2 Voltage .................................................. 36V
VON, VO2 Voltage ..................................................... 30V
FB1, FB2 .................................................................... 3V
SHDN ......................................................................... 8V
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
FB1 1
FB2 2
CT 3
SW1 4
GND 5
10 VON
9 VO2
8 SHDN
7 SW2
6 VIN
MS PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 120°C/W
ORDER PART
NUMBER
LT1947EMS
MS PART MARKING
LTUE
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.3V, VSHDN = 3.3V unless otherwise specified.
SYMBOL
Input Voltage Range
Supply Current
FB1 Voltage
FB2 Voltage
Reference Line Regulation
Error Amplifier Voltage Gain
CT Current Source
CT Threshold to Turn On Q3
FB1 Voltage to Begin CT Charge
SW1 Current Limit
SW2 Current Limit
SW1 Saturation Voltage
SW2 Saturation Voltage
SW1 Maximum Duty Cycle
SW2 Maximum Duty Cycle
Oscillator Frequency
VON Switch Drop
SW1 Leakage Current
SW2 Leakage Current
SHDN Pin Bias Current
SHDN Pin High
SHDN Pin Low
CONDITIONS
SHDN = 2.4V
SHDN = 0V
VIN = 2.7V to 8V
EA1 and EA2
VFB1 = 1.3V
(Note 3)
(Note 3)
ISW1 = 800mA
ISW2 = 300mA
IQ3 = 7mA
Switch Off, SW1 = 3.3V
Switch Off, SW2 = 3.3V
VSHDN = 2.4V
Active Mode
Shutdown Mode
MIN
2.7
1.240
q 1.225
1.225
q 1.210
4
1.25
1.17
1.1
0.35
82
q 2.3
2.4
TYP
9.5
1.26
1.26
0.01
100
5.5
1.28
1.2
1.4
0.6
0.230
0.3
85
3
160
0.01
0.01
10
MAX
8
12.5
1
1.280
1.295
1.295
1.310
0.05
6.5
1.30
1.23
2
1
0.280
0.36
3.5
200
5
5
25
0.4
UNITS
V
mA
µA
V
V
V
V
%/V
V/V
µA
V
V
A
A
V
V
%
%
MHz
mV
µA
µA
µA
V
V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1947 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Switch current limit guaranteed by design and/or correlation to
static tests.
1947f
2


Part Number LT1947
Description Adjustable Output TFT-LCD Triple Switching Regulator
Maker Linear Technology
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LT1947 Datasheet PDF






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