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PDF LT1946AEMS8E Data sheet ( Hoja de datos )
| Número de pieza | LT1946AEMS8E | |
| Descripción | 2.7MHz Boost DC/DC Converter with 1.5A Switch and Soft-Start | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT1946A
2.7MHz Boost DC/DC
Converter with 1.5A Switch
and Soft-Start
FEATURES
s 1.5A, 36V Internal Switch
s 2.7MHz Switching Frequency
s Integrated Soft-Start Function
s Adjustable Output from VIN to 35V
s Low VCESAT Switch: 300mV at 1.5A (Typical)
s 12V at 430mA from a 5V Input
s Small Thermally Enhanced 8-Lead MSOP Package
U
APPLICATIO S
s TFT-LCD Bias Supplies
s GPS Receivers
s DSL Modems
s Local Power Supply
DESCRIPTIO
The LT®1946A is a fixed frequency step-up DC/DC con-
verter containing an internal 1.5A, 36V switch. Capable of
generating 12V at 430mA from a 5V input, the LT1946A is
ideal for powering large TFT-LCD panels. The LT1946A
switches at 2.7MHz, allowing the use of tiny, low profile
inductors and low value ceramic capacitors. Loop com-
pensation can be either internal or external, giving the user
flexibility in setting loop compensation and allowing opti-
mized transient response with low ESR ceramic output
capacitors. Soft-start is controlled with an external capaci-
tor which determines the input current ramp rate during
start up. The 8-lead MSOP package and high switching
frequency ensure a low profile overall solution less than
1.1mm high.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
L1
2.2µH
D1
5V
65
OFF ON
C1
2.2µF
VIN SW
3
SHDN
2
LT1946A FB
17
VC COMP
R1
182k
RC
27.4k
SS GND*
R2
CC CSS 8
4
21k
270pF
100nF
VOUT
12V
430mA
C2
2.2µF
C1: 2.2µF, X5R or X7R, 6.3V
C2: 2.2µF, X5R or X7R, 16V
D1: MICROSEMI UPS120 OR EQUIVALENT
L1: SUMIDA CR43-2R2
* EXPOSED PAD MUST ALSO BE GROUNDED
1946A TA01
Figure 1. 5V to 12V, 430mA Step-Up DC/DC Converter
Efficiency
90
85
80
75
70
65
60
55
50
0
100 200 300 400
LOAD CURRENT (mA)
500
1946A TA01
sn1946a 1946afs
1
1 page  
BLOCK DIAGRA
LT1946A
SS VC COMP
8 17
VIN 6
VOUT
R1 (EXTERNAL)
FB
R2 (EXTERNAL)
SHDN
SHUTDOWN
3
1.25V
REFERENCE
0.5V
4µA
+
A1
–
+
A3
–
120k
90pF
COMPARATOR
–
A2
+
RQ
S
Σ
RAMP
GENERATOR
÷ 3 2.7MHz
OSCILLATOR
2
FB
Figure 2. Block Diagram
DRIVER
+
–
5 SW
Q1
0.01Ω
4 GND
EXPOSED
PAD
1946A F02
sn1946a 1946afs
5
5 Page 
TYPICAL APPLICATIO S
LT1946A
Triple Output TFT Supply Uses SEPIC Topology for Output Disconnect
D2
D3
VIN
12V ± 10%
+
L1
10µH
OFF ON
C1
2.2µF
6 5 C3
3 VIN
SHDN
SW 1µF
82
SS LT1946A FB
1
VC
COMP
GND*
CSS
100nF
74
D1
L2
10µH
C4
0.22µF
C5
0.22µF
R1
84.5k
R2
9.76k
VON
23V
10mA
VOFF
–12V
10mA
AVDD
12V
250mA
C2
20µF
C1–C5: X5R or X7R
C1: 2.2µF, 6.3V
C2: 2× 10µF, 16V
C3: 1µF, 25V
C4: 0.22µF, 25V
C5: 0.22µF, 16V
D1: MICROSEMI UPS120 OR EQUIVALENT
D2–D3: CENTRAL SEMI CMDSH-3
L1–L2: TDK RLF5018-100MR94
* EXPOSED PAD MUST ALSO BE GROUNDED
1946A TA09
2.794 ± 0.102
(.110 ± .004)
0.889 ± 0.127
(.035 ± .005)
MS8E Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1662)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
8 7 65
5.23
(.206)
MIN
2.083 ± 0.102 3.2 – 3.45
(.082 ± .004) (.126 – .136)
0.254
(.010)
DETAIL “A”
0° – 6° TYP
4.88 ± 0.1
(.192 ± .004)
0.42 ± 0.04
(.0165 ± .0015)
TYP
0.65
(.0256)
BSC
RECOMMENDED SOLDER PAD LAYOUT
GAUGE PLANE
0.53 ± 0.015
(.021 ± .006)
DETAIL “A”
1 234
1.10
(.043)
MAX
0.18
(.077)
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
0.65
(.0256)
BCS
0.52
(.206)
REF
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 ± 0.102
1 (.080 ± .004)
1.83 ± 0.102
(.072 ± .004)
3.00 ± 0.102
(.118 ± .004)
NOTE 4
8
0.86
(.34)
REF
0.13 ± 0.05
(.005 ± .002)
MSOP (MS8E) 1001
sn1946a 1946afs
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.
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LT1946AEMS8E.PDF ] | |
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