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Linear Technology Electronic Components Datasheet

LT1946 Datasheet

1.2MHz Boost DC/DC Converter

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LT1946
1.2MHz Boost
DC/DC Converter with
1.5A Switch and Soft-Start
FEATURES
s 1.5A, 36V Internal Switch
s 1.2MHz Switching Frequency
s Integrated Soft-Start Function
s Output Voltage Up to 34V
s Low VCESAT Switch: 300mV at 1.5A (Typ)
s 8V at 430mA from a 3.3V Input
s Small 8-Lead MSOP Package
U
APPLICATIO S
s TFT-LCD Bias Supplies
s GPS Receivers
s DSL Modems
s Local Power Supplies
DESCRIPTIO
The LT®1946 is a fixed frequency step-up DC/DC converter
containing an internal 1.5A, 36V switch. Capable of gener-
ating 8V at 430mA from a 3.3V input, the LT1946 is ideal
for large TFT-LCD panel power supplies. The LT1946
switches at 1.2MHz, 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 1.2mm high.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
L1
4.7µH
D1
3.3V
65
3 VIN
OFF ON
SHDN
SW
C1
2.2µF
RC
49.9k
CC
470pF
LT1946
12
VC FB
SS COMP GND
CSS 8 7 4
100nF
C1: 2.2µF, X5R OR X7R, 6.3V
C2: 2 × 10µF, X5R OR X7R, 10V
D1: MICROSEMI UPS120 OR EQUIVALENT
L1: TDK RLF5018T-4R7M1R4
R1
28.7k
R2
5.23k
VOUT
8V
430mA
C2
20µF
1946 F01
Figure 1. 3.3V to 8V, 430mA Step-Up DC/DC Converter
Efficiency
90
85
80
75
70
65
60
55
50
0 100 200 300 400 500
LOAD CURRENT (mA)
1946 F01b
sn1946 1946fs
1


Linear Technology Electronic Components Datasheet

LT1946 Datasheet

1.2MHz Boost DC/DC Converter

No Preview Available !

LT1946
ABSOLUTE AXI U RATI GS
(Note 1)
VIN Voltage ............................................................. 16V
SW Voltage ............................................... – 0.4V to 36V
FB Voltage ............................................................. 2.5V
SHDN Voltage ......................................................... 16V
Current Into FB Pin .............................................. ±1mA
Maximum Junction Temperature ......................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
VC 1
FB 2
SHDN 3
GND 4
TOP VIEW
8 SS
7 COMP
6 VIN
5 SW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 125°C/W
(4-LAYER BOARD)
ORDER PART
NUMBER
LT1946EMS8
MS8 PART MARKING
LTUG
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 = 3V, VSHDN = VIN unless otherwise specified. (Note 2)
SYMBOL
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage
FB Pin Bias Current
Error Amp Transconductance
Error Amp Voltage Gain
Quiescent Current
Quiescent Current in Shutdown
Reference Line Regulation
Switching Frequency
Switching Frequency in Foldback
Maximum Duty Cycle
Switch Current Limit
Switch VCESAT
Switch Leakage Current
Soft-Start Charging Current
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Bias Current
CONDITIONS
VFB = 1.250V (Note 3)
I = 2µA
VSHDN = 2.5V, Not Switching
VSHDN = 0V, VIN = 3V
2.6V VIN 16V
VFB = 0V
(Note 4)
ISW = 1A
VSW = 5V
VSS = 0.5V
VSHDN = 3V
VSHDN = 0V
MIN
1.230
q 1.220
q
0.9
q 0.8
q 86
q 1.5
2.5
2.4
TYP
2.45
1.250
20
40
300
3.2
0
0.01
1.2
0.4
90
2.1
240
0.01
4
16
0
MAX
2.6
16
1.270
1.270
120
5
1
0.05
1.4
1.5
3.1
340
1
6
0.5
32
0.1
UNITS
V
V
V
V
nA
µmhos
V/V
mA
µA
%/V
MHz
MHz
MHz
%
A
mV
µA
µA
V
V
µA
µA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1946E 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: Current flows out of FB pin.
Note 4: Current limit guaranteed by design and/or correlation to static test.
Current limit is independent of duty cycle and is guaranteed by design.
2
sn1946 1946fs


Part Number LT1946
Description 1.2MHz Boost DC/DC Converter
Maker Linear Technology
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LT1946 Datasheet PDF





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