QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 620
HIGH CURRENT QUAD OUTPUT SWITCHING REGULATORS FOR TFT-LCD PANELS
LT1943
DESCRIPTION
Demonstration circuit 620 is a quad output power
supply intended for use in large TFT-LCD panels. The
circuit features the LT
®
1943 high current quad-output
switching regulator and generates a 3.3V logic supply
along with the triple output supply required for the
TFT-LCD panels. With an input voltage range of 8V to
20V, a step down regulator provides 3.3V V
LOGIC
with
up to 2A current; a high power SEPIC converter, a
lower power boost converter and an inverting
converter provide three independent output voltages
AV
DD
, V
ON
and V
OFF
required by the LCD panels. A high
side PNP provides delayed turn on of the V
ON
signal
and can source up to 30mA at 30V.
All four switchers are synchronized to the internal
1.2MHz clock, allowing the use of low profile
inductors and ceramic capacitors. They all have soft-
start to limit start-up inrush current.
Long wires run from input sources (such as wall
adaptors) can cause large voltage spikes during initial
plug-in. C17 is installed on DC620 to damp the
possible voltage spikes. C17 is not required for
applications when input source is close to the
regulator. Please refer to Application Note 88 for
details.
Design files for this circuit board are available.
Call the LTC factory.
LT is a registered trademark of Linear Technology Corporation
Table 1.
PARAMETER
Performance Summary (T
A
= 25°C unless otherwise noted)
CONDITION
-40°C to 85°C
-40°C to 85°C
V
IN
= 8V to 20V, I
OUT
= 0A to 2A
V
IN
= 8V to 20V (Note 1)
V
IN
= 12V, load at V
LOGIC
= 2A (20MHz BW)
V
IN
= 12V, load at AV
DD
= 500mA (20MHz BW)
VALUE
8V
20V
3.3V ±3%
2A
23mV
P–P
64mV
P–P
1.2MHz
Logic Low Voltage-Off, -40°C to 85°C
0.4V MAX
2.4V MIN
Minimum Input Voltage
Maximum Input Voltage
Output Voltage V
LOGIC
Maximum Output Current at V
LOGIC
Typical Output Ripple V
LOGIC
Typical Output Ripple AV
DD
Typical Switching Frequency
On/Off Control
Logic High Voltage-On
Note 1:
2A maximum output current is guaranteed when V
OFF
is unloaded. Since V
OFF
is supplied from V
LOGIC
, the load at V
OFF
reduces the available cur-
rent at V
LOGIC
. More output current is available at higher input voltage. Please refer to the LT1943 data sheet for output current vs. input voltage
curve.
QUICK START PROCEDURE
Demonstration circuit 620 is easy to set up to
evaluate the performance of the LT1943. Refer to
Figure 1 for proper measurement equipment setup
and follow the procedure below:
NOTE:
When measuring the input or output
voltage ripple, care must be taken to avoid a long
ground lead on the oscilloscope probe. Measure
the input or output voltage ripple by touching the
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 620
HIGH CURRENT QUAD OUTPUT SWITCHING REGULATORS FOR TFT-LCD PANELS
probe tip directly across the V
IN
or V
OUT
and
GND terminals. See Figure 2 for proper scope
probe technique.
1.
Make sure the input voltage does not exceed 20V.
3.
Check for the proper output voltages. If there is no
output, temporarily disconnect the load to make
sure that the load is not set too high.
4.
Once the proper output voltages are established,
With power off, connect the input power supply to
V
IN
and GND.
2.
Turn on the power at the input.
adjust the loads within the operating range and ob-
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
VIN
GND
2
Linear Technology Corporation
LT1943EFE
Bill Of Material
Demo Bd. #620A
6/17/2005
Item Qty Reference
Part Description
Manufacture / Part #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
1
1
1
1
2
1
1
1
1
3
1
1
1
1
4
0
1
1
1
1
1
2
1
11
1
2
1
1
1
1
4
1
1
1
1
1
C1
C8
C2
C3
C5,C4
C6
C7
C9
C10
C11,C12,C14
C13
C15
C16
C17
C20-C23
C18,C19 (OPT.)
C24
C25
C26
D1
D2
D3,D6
D5
E1-E11
L1
L2,L3
L4
L6
R10
R11
R1,R5,R8,R4
R12
R13
R2
R3
R6
CAP., X5R, 10uF, 25V, 20% 1210
CAP., X5R, 10uF, 16V, 20% 1210
CAP., X5R, 22uF, 6.3V, 20% 1206
CAP., X7R, 0.22uF, 10V, 20% 0603
CAP., X7R, 0.015uF, 16V, 20%, 0402
CAP., X7R, 2.2uF, 10V, 10% 0805
CAP., X5R, 0.47uF, 16V, 20% 0603
CAP., X5R, 0.047uF, 16V, 10% 0402
CAP., X5R, 2.2uF, 35V, 20% 1210
CAP., X7R, 2200pF, 50V, 20% 0402
CAP., X7R, 680pF, 50V, 20% 0402
CAP., X5R, 0.47uF, 35V, 20% 0805
CAP., X5R, 1.0uF, 25V, 10% 0805
CAP., TANT, 47uF, 35V, 20% 7343
CAP., X7R, 100pF, 50V, 20%, 0402
CAP.,
0402
CAP., NPO, 10pF, 50V, 10% 0402
CAP., X5R, 1.0uF, 16V, 20% 0805
CAP., X7R, 1.0uF, 10V, 20% 0805
Schottky Barrier REC., B230A
SMA
Schottky Diode, CMDSH-3
SOD-323
Schottky Barries Dio., ZHCS400, SOD-323
Schottky Barrier REC., B240A
SMA
TURRET,
INDUCTOR, 4.7uH
RLF7030
INDUCTOR, 10uH
SLF6028
INDUCTOR, 10uH
RLF5018
INDUCTOR, 33uH
RLF5018
RES., CHIP, 18K, 1/16W, 5% 0402
RES., CHIP, 6.8K, 1/16W, 5% 0402
RES., CHIP, 10K, 1/16W, 1% 0402
RES., CHIP, 27K, 1/16W, 5% 0402
RES., CHIP, 13K, 1/16W, 5% 0402
RES., CHIP, 16.2K, 1/16W, 1% 0402
RES., CHIP, 80.6K, 1/16W, 1% 0402
RES., CHIP, 95.3K, 1/16W, 1% 0402
Page 1 - of - 2
Taiyo Yuden, TMK325BJ106MM
Taiyo Yuden, EMK325BJ106MN
Taiyo Yuden, JMK316BJ226ML
AVX, 0603ZC224MAT2A
AVX, 0402YC153MAT2A
MuRata, GRM21BR71A225KA01L
AVX, 0603YD474MAT2A
AVX, 0402YD473KAT2A
Taiyo Yuden, GMK325BJ225MN
AVX, 04025C222MAT2A
AVX, 04025C681MAT2A
Taiyo Yuden, GMK212BJ474MG
AVX, 08053D105KAT2A
AVX, TAJE476M035R
AVX, 04025C101MAT2A
AVX, 04025A100KAT2A
TAIYO YUDEN, EMK212BJ105MG
TAIYO YUDEN, LMK212BJ105MG
Diodes Inc., B230A
CENTRAL SEMI., CMDSH-3-LTC
ZETEX, ZHCS400
Diodes Inc., B240A
MILL-MAX, 2501-2
TDK, RLF7030T-4R7M3R4
TDK, SLF6028T-100M1R3
TDK, RLF5018T-100MR94
TDK, RLF5018T-330MR51
AAC, CR05-183JM
AAC, CR05-682JM
AAC, CR05-1002FM
AAC, CR05-273JM
AAC, CR05-133JM
AAC, CR05-1622FM
AAC, CR05-8062FM
AAC, CR05-9532FM
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