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Linear Technology Electronic Components Datasheet

LT1946A Datasheet

2.7MHz Boost DC/DC Converter

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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


Linear Technology Electronic Components Datasheet

LT1946A Datasheet

2.7MHz Boost DC/DC Converter

No Preview Available !

LT1946A
ABSOLUTE AXI U RATI GS
(Note 1)
VIN Voltage .............................................................. 16V
SW Voltage ................................................– 0.4V to 36V
FB Voltage .............................................................. 2.5V
Current into FB Pin ............................................... ±1mA
SHDN Voltage .......................................................... 16V
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
TOP VIEW
VC 1
FB 2
SHDN 3
GND 4
8 SS
7 COMP
6 VIN
5 SW
MS8E PACKAGE
8-LEAD PLASTIC MSOP
EXPOSED PAD IS GROUND
(MUST BE SOLDERED TO PCB)
TJMAX = 125°C, θJA = 40°C/W,
θJC = 10°C/W
ORDER PART
NUMBER
LT1946AEMS8E
MS8E PART
MARKING
LTYZ
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 noted. (Note 2)
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage
CONDITIONS
FB Pin Bias Current
Error Amp Transconductance
Error Amp Voltage Gain
Quiescent Current
Quiescent Current in Shutdown
Reference Line Regulation
Switching Frequency
VFB = 1.25V (Note 3)
I = 2µA
VSHDN = 2.5V, Not Switching
VSHDN = 0V, VIN = 3V
2.6V VIN 16V
Switching Frequency in Foldback
Maximum Duty Cycle
VFB = 0V
Switch Current Limit
(Note 4)
Switch VCESAT
Switch Leakage Current
Soft-Start Charging Current
SHDN Input Voltage High
ISW = 1A
VSW = 5V
VSS = 0.5V
SHDN Input Voltage Low
SHDN Pin Bias Current
VSHDN = 3V
VSHDN = 0V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1946AE is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
MIN TYP MAX UNITS
2.45 2.6
V
16 V
1.23 1.25 1.27
q 1.22
1.27
V
V
q
20 120
nA
40 µmhos
300 V/V
3.6 5
mA
2.4
q 2.3
01
0.01 0.05
2.7 3
3.1
µA
%/V
MHz
MHz
0.85 MHz
q 73
80
%
q 1.5 2.1 3.1
240 340
0.01 1
2.5 4
6
2.4
A
mV
µA
µA
V
0.5
16 32
0 0.1
V
µA
µA
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Current flows out of the 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.
sn1946a 1946afs
2


Part Number LT1946A
Description 2.7MHz Boost DC/DC Converter
Maker Linear Technology
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LT1946A Datasheet PDF






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