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LT1944-1EMS#TRPBF

P1-P3P4-P6P7-P8
1
LT1944-1
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
Dual Micropower Step-Up
DC/DC Converter
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.
■
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
Switches: 85mV at 70mA
■
Uses Small Surface Mount Components
■
High Output Voltage: Up to 34V
■
Tiny 10-Pin MSOP Package
■
Small TFT LCD Panels
■
Handheld Computers
■
Battery Backup
■
Digital Cameras
, LTC and LT are registered trademarks of Linear Technology Corporation.
V
IN
SW2
FB1
LT1944-1
2
3
L1
22µH
D1
SHDN1
324k
1M
C2
4.7µF
5V
40mA
15V
2.5mA
–10V
1mA
V
IN
2.7V
TO 4.2V
1944-1 TA01
GND
7
PGND
9
PGND
10
86
SW1
4.7pF
C1
4.7µF
FB2
4
1
5
SHDN2
L2
22µH
D2
D3
D4
2M
178k
C3
1µF
4.7pF
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
C5
0.1µF
C4
1µF
5V
LOAD CURRENT (mA)
0.1
EFFICIENCY (%)
1 10 100
1944-1 TA01a
90
85
80
75
70
65
60
55
50
V
IN
= 4.2V
V
IN
= 2.7V
Triple Output Power Supply (5V, 15V, –10V) for LCD Displays
5V Output Efficiency
2
LT1944-1
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
LT1944-1EMS
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, Switcher 1 (Note 4) V
FB
> 1V 400 ns
V
FB
< 0.6V 1.5 µs
Switch Off Time, Switcher 2 (Note 4) V
FB
> 1V 1.5 µs
V
FB
< 0.6V 1.5 µs
Switch V
CESAT
I
SW
= 70mA 85 120 mV
Switch Current Limit, Switcher 1 65 100 125 mA
Switch Current Limit, Switcher 2 130 175 225 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 LT1944-1E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
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.
LTTU
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
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.
3
LT1944-1
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Switch Saturation Voltage
(V
CESAT
) Quiescent Current
Feedback Pin Voltage and
Bias Current
TEMPERATURE (°C)
–50
FEEDBACK VOLTAGE (V)
1944-1 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)
1944-1 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.
SHUTDOWN PIN VOLTAGE (V)
SHUTDOWN PIN CURRENT (µA)
1944-1 G03
25
20
15
10
5
0
0 5 10 15
25°C
100°C
Switch Off Time Shutdown Pin CurrentSwitch Current Limit
TEMPERATURE (°C)
–50
SWITCH VOLTAGE (V)
0.15
0.13
0.10
0.08
0.05
0.03
0
–25
02550
1944-1 G01
75 100
I
SWITCH
= 100mA
I
SWITCH
= 70mA
TEMPERATURE (°C)
–50
SWITCH OFF TIME (ns)
–25
0
25 50 75
2000
1800
1600
1400
1200
1000
800
600
400
200
0
100
SWITCHER 2
SWITCHER 1
1944-1 G04
TEMPERATURE (°C)
–50
PEAK CURRENT (mA)
200
175
150
125
100
75
50
–25
02550
1944-1 G05
75 100
V
IN
= 12V
V
IN
= 1.2V
V
IN
= 12V
V
IN
= 1.2V
SWITCHER 1
SWITCHER 2
P1-P3P4-P6P7-P8

LT1944-1EMS#TRPBF

Mfr. #:
Buy LT1944-1EMS#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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