LT1946
1.2MHz Boost
DC/DC Converter with
1.5A Switch and Soft-Start
FEATURES DESCRIPTIO
1.5A, 36V Internal Switch
The LT 1946 is a fixed frequency step-up DC/DC converter
1.2MHz Switching Frequency
containing an internal 1.5A, 36V switch. Capable of gener-
Integrated Soft-Start Function
ating 8V at 430mA from a 3.3V input, the LT1946 is ideal
Output Voltage Up to 34V
for large TFT-LCD panel power supplies. The LT1946
Low V Switch: 300mV at 1.5A (Typ)
switches at 1.2MHz, allowing the use of tiny, low profile
CESAT
8V at 430mA from a 3.3V Input
inductors and low value ceramic capacitors. Loop com-
Small 8-Lead MSOP Package
pensation can be either internal or external, giving the user
flexibility in setting loop compensation and allowing opti-
U
mized transient response with low ESR ceramic output
APPLICATIO S
capacitors. Soft-start is controlled with an external capaci-
tor, which determines the input current ramp rate during
TFT-LCD Bias Supplies
start-up.
GPS Receivers
DSL Modems
The 8-lead MSOP package and high switching frequency
Local Power Supplies
ensure a low profile overall solution less than 1.2mm high.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
Efficiency
90
D1
4.7H
V
OUT
V
IN
85
8V
3.3V
430mA
80
V SW
IN
28.7k
OFF ON SHDN
75
LT1946
2.2F
70
FB
V 20F
C
49.9k
SS COMP GND
65
5.23k
60
470pF 100nF
55
1946 F01
C1: 2.2F, X5R OR X7R, 6.3V
C2: 2 10F, X5R OR X7R, 10V 50
0 100 200 400 500
300
D1: MICROSEMI UPS120 OR EQUIVALENT
L1: TDK RLF5018T-4R7M1R4
LOAD CURRENT (mA)
1946 F01b
Figure 1. 3.3V to 8V, 430mA Step-Up DC/DC Converter
1946fb
1
EFFICIENCY (%)
U
ULT1946
ABSOLUTE AXI U RATI GS
(Note 1)
V Voltage ............................................................. 16V Maximum Junction Temperature ......................... 125C
IN
SW Voltage ............................................... 0.4V to 36V Operating Temperature Range (Note 2) .. 40C to 85C
FB Voltage ............................................................. 2.5V Storage Temperature Range ................ 65C to 150C
SHDN Voltage ......................................................... 16V Lead Temperature (Soldering, 10 sec)................. 300C
Current Into FB Pin .............................................. 1mA
UUW
PACKAGE/ORDER I FOR ATIO
ORDER PART ORDER PART
TOP VIEW
V 1 8 SS NUMBER NUMBER
TOP VIEW
C
FB 2 7 COMP
9
V 1 8 SS
C
SHDN 3 6 V
IN
LT1946EMS8E FB 2 7 COMP LT1946EMS8
5 SW
GND 4
SHDN 3 6 V
IN
5 SW
MS8E PACKAGE GND 4
8-LEAD PLASTIC MSOP
MS8 PACKAGE
MS8 PART MARKING
EXPOSED PAD (PIN 9) IS GROUND
MS8 PART MARKING
8-LEAD PLASTIC MSOP
(MUST BE SOLDERED TO PCB)
T = 125C, = 125C/W
LTBNW JMAX JA LTUG
T = 125C, = 40C/W,
JMAX JA
(4-LAYER BOARD)
= 10C/W
JC
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: