LT1945_15 Datasheet, PDF (1/8 Pages) Linear Technology – Dual Micropower DC/DC Converter with Positive and Negative Outputs

FEATURES
n _{Generates Well-Regulated Positive and}
Negative Outputs
n _{Low Quiescent Current:}
20μA in Active Mode (per Converter)
<1μA in Shutdown Mode
n _{Operates with VIN as Low as 1.2V}
n _{Low VCESAT Switch: 250mV at 300mA}
n _{Uses Small Surface Mount Components}
n _{High Output Voltage: Up to ±34V}
n _{Tiny 10-Pin MSOP Package}
APPLICATIONS
n _{Small TFT LCD Panels}
n _{Handheld Computers}
n _{Battery Backup}
n _{Digital Cameras}
LT1945
Dual Micropower DC/DC
Converter with Positive and
Negative Outputs
DESCRIPTION
The LT^®1945 is a dual micropower DC/DC converter 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 LT1945 ideal for a wide variety of ap-
plications. 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, 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
without the use of costly transformers. The LT1945’s
low off-time of 400ns permits the use of tiny, low profile
inductors and capacitors to minimize footprint and cost
in space-conscious portable applications.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Output (+12V, –20V) Converter
V_IN
2.7V
TO 5V
C1
4.7μF
L1
10μH
C4
0.1μF _D1
8
10
V_IN
2
SHDN1
SW1
1
NFB1
LT1945
D2
4
SHDN2
5
FB2
GND PGND PGND SW2
37 96
100pF _365k
24.9k
–20V
10mA
C2
1μF
L2
10μH
C1: TAIYO YUDEN JMK212BJ475
C2, C3: TAIYO YUDEN TMK316BJ105
C4: TAIYO YUDEN EMK107BJ104
D1, D2, D3: ZETEX ZHCS400
L1, L2: MURATA LQH3C100
4.7pF
D3
115k
1M
C3
1μF
12V
20mA
1945 TA01
90
85
80
75
70
65
60
55
50
0.1
Efficiency at V_IN = 3.6V
+12V OUTPUT
–20V OUTPUT
1
10
LOAD CURRENT (mA)
100
1945 TA01a
1945fa
1