LT1944 LINER [Linear Technology], LT1944 Datasheet - Page 3

• Manufacturer Part Number: LT1944
• Description: Dual Micropower Step-Up DC/DC Converter
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
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.
TYPICAL PERFOR A CE CHARACTERISTICS
U
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
550
500
450
400
350
300
250
–50
–50
Switch Saturation Voltage
(V
Switch Off Time
CESAT
–25
–25
U
)
TEMPERATURE ( C)
TEMPERATURE ( C)
0
0
V
IN
I
I
SWITCH
SWITCH
= 1.2V
25
U
25
V
IN
= 12V
= 500mA
= 300mA
50
50
W
75
75
1944 G01
1944 G04
U
100
100
1.25
1.24
1.23
1.22
1.21
1.20
400
350
300
250
200
150
100
50
0
–50
–50
Feedback Pin Voltage and
Bias Current
Switch Current Limit
V
–25
IN
–25
= 12V
TEMPERATURE ( C)
TEMPERATURE ( C)
0
0
VOLTAGE
CURRENT
25
25
V
IN
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
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.
= 1.2V
IN
50
50
(Pin 8): Input Supply Pin. Bypass this pin with a
75
75
1944 G02
1944 G05
100
100
50
40
30
20
10
0
25
20
15
10
25
23
21
19
17
15
5
0
–50
Quiescent Current
Shutdown Pin Current
0
V
NOT SWITCHING
FB
= 1.23V
–25
SHUTDOWN PIN VOLTAGE (V)
TEMPERATURE ( C)
5
0
25 C
V
IN
= 12V
25
V
IN
100 C
LT1944
= 1.2V
10
50
75
1944 G03
1944 G03
3
100
15