LT1944-1 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 Switches: 85mV at 70mA}
s _{Uses Small Surface Mount Components}
s _{High Output Voltage: Up to 34V}
s _{Tiny 10-Pin MSOP Package}
U
APPLICATIO S
s _{Small TFT LCD Panels}
s _{Handheld Computers}
s _{Battery Backup}
s _{Digital Cameras}
LT1944-1
Dual Micropower Step-Up
DC/DC Converter
DESCRIPTIO
The LT^®1944-1 is a dual micropower step-up DC/DC
converter in a 10-pin MSOP package. One converter is
designed with a 100mA current limit and a 400ns off-time;
the other with a 175mA current limit and a 1.5µs off-time.
The 1.5µs off-time converter is ideal for generating an
output voltage that is close to the input voltage (i.e. a Li-
Ion to 5V converter, or a two-cell to 3.3V converter). With
an input voltage range of 1.2V to 15V, the LT1944-1 is ideal
for a wide variety of applications. Both converters feature
a quiescent 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, result-
ing in high efficiency over a broad range of load current.
Tiny, low profile inductors and capacitors can be used to
minimize footprint and cost in space-conscious portable
applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Triple Output Power Supply (5V, 15V, –10V) for LCD Displays
V_IN
2.7V
TO 4.2V
C1
4.7µF
L1
22µH
D1
8
V_IN
4
SHDN2
6
4.7pF
SW2
5
FB2
LT1944-1
2
SHDN1
1
FB1
GND PGND PGND SW1
3 7 9 10
5V
40mA
1M
C2
4.7µF
324k
178k
L2
22µH
C1, C2: TAIYO YUDEN JMK212BJ475
C3, C4: TAIYO YUDEN EMK212BJ105
C5: TAIYO YUDEN EMK107BJ104
D1, D2, D3, D4: CENTRAL SEMI CMDSH3
L1, L2: MURATA LQH3C220
4.7pF
2M
D2
C5
0.1µF
D3
5V
D4
C3
1µF
15V
2.5mA
C4
1µF
–10V
1944-1 TA01 1mA
90
85
80
75
70
65
60
55
50
0.1
5V Output Efficiency
V_IN = 4.2V
V_IN = 2.7V
1
10
LOAD CURRENT (mA)
100
1944-1 TA01a
1