LT1944_15 Datasheet, PDF (1/8 Pages) Linear Technology – Dual Micropower Step-Up DC/DC Converter

FEATURES
s _{Low Quiescent Current:}
20µA in Active Mode
<1µA in Shutdown Mode
s _{Operates with VIN as Low as 1.2V}
s _{Low VCESAT Switch: 250mV at 300mA}
s _{Uses Small Surface Mount Components}
s _{High Output Voltage: Up to 34V}
s _{Tiny 10-Pin MSOP Package}
U
APPLICATIO S
s _{LCD Bias}
s _{Handheld Computers}
s _{Battery Backup}
s _{Digital Cameras}
LT1944
Dual Micropower Step-Up
DC/DC Converter
DESCRIPTIO
The LT^®1944 is a dual micropower step-up DC/DC con-
verter in a 10-pin MSOP package. Each converter is
designed with a 350mA current limit and an input voltage
range of 1.2V to 15V, making the LT1944 ideal for a wide
variety of applications. Both converters feature a quies-
cent current of only 20µA at no load, which further reduces
to 0.5µA in shutdown. A current limited, fixed off-time
control scheme conserves operating current, resulting in
high efficiency over a broad range of load current. The 36V
switch allows high voltage outputs up to 34V to be easily
generated in a simple boost topology without the use of
costly transformers. The LT1944’s low off-time of 400ns
permits the use of tiny, low profile inductors and capaci-
tors to minimize footprint and cost in space-conscious
portable applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
V_IN
2.7V
TO 4.2V
C1
4.7µF
Dual Output (5V, 30V) Boost Converter
L1
4.7µH
D1
8
V_IN
2
SHDN1
10
4.7pF
SW1
1M
1
FB1
LT1944
4
5
SHDN2
FB2
324k
GND PGND PGND SW2
37 96
86.6k
L2
10µH
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN JMK316BJ106
C3: TAIYO YUDEN GMK316BJ105
D1, D2: ON SEMI MBR0540
L1: MURATA LQH3C4R7
L2: MURATA LQH3C100
4.7pF
2M
D2
5V
80mA
C2
10µF
C3
1µF
30V
8mA
1944 TA01
5V Output Efficiency
90
85
V_IN = 4.2V
80
75
V_IN = 2.7V
70
65
60
55
50
0.1
1
10
LOAD CURRENT (mA)
100
1944 TA01a
1