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LT1944EMS#TRPBF

P1-P3P4-P6P7-P8
1
LT1944
Dual Micropower Step-Up
DC/DC Converter
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.
■
Low Quiescent Current:
20
µ
A in Active Mode
<1
µ
A in Shutdown Mode
■
Operates with V
IN
as Low as 1.2V
■
Low V
CESAT
Switch: 250mV at 300mA
■
Uses Small Surface Mount Components
■
High Output Voltage: Up to 34V
■
Tiny 10-Pin MSOP Package
■
LCD Bias
■
Handheld Computers
■
Battery Backup
■
Digital Cameras
, LTC and LT are registered trademarks of Linear Technology Corporation.
V
IN
SW1
FB2
LT1944
4
3
L1
4.7µH
D1
SHDN2
324k
1M
C2
10µF
5V
80mA
30V
8mA
V
IN
2.7V
TO 4.2V
1944 TA01
GND
7
PGND
9
PGND
6
810
SW2
4.7pF
C1
4.7µF
FB1
2
5
1
SHDN1
L2
10µH
D2
2M
86.6k
C3
1µF
4.7pF
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN JMK316BJ106
C3: TAIYO YUDEN GMK316BJ105
D1, D2: ON SEMI MBR0540
L1: MURATA LQH3C4R7
L2: MURATA LQH3C100
LOAD CURRENT (mA)
0.1
EFFICIENCY (%)
1 10 100
1944 TA01a
90
85
80
75
70
65
60
55
50
V
IN
= 4.2V
V
IN
= 2.7V
Dual Output (5V, 30V) Boost Converter 5V Output Efficiency
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LT1944
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
V
IN
, SHDN1, SHDN2 Voltage ................................... 15V
SW1, SW2 Voltage .................................................. 36V
FB1, FB2 Voltage .......................................................V
IN
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
ORDER PART
NUMBER
LT1944EMS
MS10 PART
MARKING
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage 1.2 V
Quiescent Current, Each Switcher Not Switching 20 30 µA
V
SHDN
= 0V 1 µA
FB Comparator Trip Point ● 1.205 1.23 1.255 V
FB Comparator Hysteresis 8mV
FB Voltage Line Regulation 1.2V < V
IN
< 12V 0.05 0.1 %/V
FB Pin Bias Current (Note 3) V
FB
= 1.23V ● 30 80 nA
Switch Off Time V
FB
> 1V 400 ns
V
FB
< 0.6V 1.5 µs
Switch V
CESAT
I
SW
= 300mA 250 350 mV
Switch Current Limit 250 350 400 mA
SHDN Pin Current V
SHDN
= 1.2V 2 3 µA
V
SHDN
= 5V 8 12 µA
SHDN Input Voltage High 0.9 V
SHDN Input Voltage Low 0.25 V
Switch Leakage Current Switch Off, V
SW
= 5V 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 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.
T
JMAX
= 125°C, θ
JA
= 160°C/W
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 1.2V, V
SHDN
= 1.2V unless otherwise noted.
LTTR
1
2
3
4
5
FB1
SHDN1
GND
SHDN2
FB2
10
9
8
7
6
SW1
PGND
V
IN
PGND
SW2
TOP VIEW
MS10 PACKAGE
10-LEAD PLASTIC MSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges.
3
LT1944
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Switch Saturation Voltage
(V
CESAT
) Quiescent Current
Feedback Pin Voltage and
Bias Current
TEMPERATURE (°C)
–50
–25 0 25 50 75 100
SWITCH VOLTAGE (V)
1944 G01
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
I
SWITCH
= 500mA
I
SWITCH
= 300mA
TEMPERATURE (°C)
–50
FEEDBACK VOLTAGE (V)
1944 G02
1.25
1.24
1.23
1.22
1.21
1.20
BIAS CURRENT (nA)
50
40
30
20
10
0
CURRENT
VOLTAGE
–25 0 25 50 75 100
TEMPERATURE (°C)
QUIESCENT CURRENT (µA)
1944 G03
25
23
21
19
17
15
–50 –25 0 25 50 75 100
V
IN
= 12V
V
IN
= 1.2V
V
FB
= 1.23V
NOT SWITCHING
PI FU CTIO S
UUU
FB1 (Pin 1): Feedback Pin for Switcher 1. Set the output
voltage by selecting values for R1 and R2.
SHDN1 (Pin 2): Shutdown Pin for Switcher 1. Tie this pin
to 0.9V or higher to enable device. Tie below 0.25V to turn
it off.
GND (Pin 3): Ground. Tie this pin directly to the local
ground plane.
SHDN2 (Pin 4): Shutdown Pin for Switcher 2. Tie this pin
to 0.9V or higher to enable device. Tie below 0.25V to turn
it off.
FB2 (Pin 5): Feedback Pin for Switcher 2. Set the output
voltage by selecting values for R1B and R2B.
SW2 (Pin 6): Switch Pin for Switcher 2. This is the
collector of the internal NPN power switch. Minimize the
metal trace area connected to the pin to minimize EMI.
PGND (Pins 7, 9): Power Ground. Tie these pins directly
to the local ground plane. Both pins must be tied.
V
IN
(Pin 8): Input Supply Pin. Bypass this pin with a
capacitor as close to the device as possible.
SW1 (Pin 10): Switch Pin for Switcher 1. This is the
collector of the internal NPN power switch. Minimize the
metal trace area connected to the pin to minimize EMI.
TEMPERATURE (°C)
SWITCH OFF TIME (ns)
1944 G04
550
500
450
400
350
300
250
–50 –25 0 25 50 75 100
V
IN
= 1.2V
V
IN
= 12V
TEMPERATURE (°C)
PEAK CURRENT (mA)
1944 G05
400
350
300
250
200
150
100
50
0
–50 –25 0 25 50 75 100
V
IN
= 12V
V
IN
= 1.2V
SHUTDOWN PIN VOLTAGE (V)
SHUTDOWN PIN CURRENT (µA)
1944 G03
25
20
15
10
5
0
0 5 10 15
25°C
100°C
Switch Off Time Shutdown Pin CurrentSwitch Current Limit
P1-P3P4-P6P7-P8

LT1944EMS#TRPBF

Mfr. #:
Buy LT1944EMS#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 2x uP Boost DC/DC Conv
Lifecycle:
New from this manufacturer.
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