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Linear Technology Electronic Components Datasheet

LT1944-1 Datasheet

Dual Micropower Step-Up DC/DC Converter

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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
VIN
2.7V
TO 4.2V
C1
4.7µF
L1
22µH
D1
8
VIN
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
D2
2M
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
VIN = 4.2V
VIN = 2.7V
1 10
LOAD CURRENT (mA)
100
1944-1 TA01a
1


Linear Technology Electronic Components Datasheet

LT1944-1 Datasheet

Dual Micropower Step-Up DC/DC Converter

No Preview Available !

LT1944-1
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, SHDN1, SHDN2 Voltage ................................... 15V
SW1, SW2 Voltage .................................................. 36V
FB1, FB2 Voltage .......................................................VIN
Current into FB1, FB2 Pins ..................................... 1mA
Junction Temperature ........................................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
FB1 1
SHDN1 2
GND 3
SHDN2 4
FB2 5
TOP VIEW
10 SW1
9 PGND
8 VIN
7 PGND
6 SW2
MS10 PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 160°C/W
ORDER PART
NUMBER
LT1944-1EMS
MS10 PART
MARKING
LTTU
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VSHDN = 1.2V unless otherwise noted.
PARAMETER
Minimum Input Voltage
Quiescent Current, Each Switcher
FB Comparator Trip Point
FB Comparator Hysteresis
FB Voltage Line Regulation
FB Pin Bias Current (Note 3)
Switch Off Time, Switcher 1 (Note 4)
Switch Off Time, Switcher 2 (Note 4)
Switch VCESAT
Switch Current Limit, Switcher 1
Switch Current Limit, Switcher 2
SHDN Pin Current
SHDN Input Voltage High
SHDN Input Voltage Low
Switch Leakage Current
CONDITIONS
Not Switching
VSHDN = 0V
1.2V < VIN < 12V
VFB = 1.23V
VFB > 1V
VFB < 0.6V
VFB > 1V
VFB < 0.6V
ISW = 70mA
VSHDN = 1.2V
VSHDN = 5V
Switch Off, VSW = 5V
MIN TYP MAX UNITS
1.2 V
20 30
1
µA
µA
q 1.205 1.23 1.255
V
8 mV
0.05 0.1
%/V
q
30 80
nA
400 ns
1.5 µs
1.5 µs
1.5 µs
85 120
mV
65 100 125
mA
130 175 225
mA
23
8 12
µA
µA
0.9 V
0.25 V
0.01 5
µA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1944-1E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Bias current flows into the FB pin.
Note 4: See Figure 1 for Switcher 1 and Switcher 2 locations.
2


Part Number LT1944-1
Description Dual Micropower Step-Up DC/DC Converter
Maker Linear
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