LT1946 Datasheet, PDF (1/12 Pages) Linear Technology – 1.2MHz Boost DC/DC Converter with 1.5A Switch and Soft-Start

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
V_IN
L1
4.7µH
D1
3.3V
6
5
3 ^VIN
SW
OFF ON
SHDN
C1
2.2µF
R_C
49.9k
C_C
470pF
LT1946
1
2
V_C
FB
SS COMP GND
C_SS 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
V_OUT
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