lt1931a Linear Technology Corporation, lt1931a Datasheet - Page 3

• Manufacturer Part Number: lt1931a
• Description: Lt1931a - 1.2mhz/2.2mhz Inverting Dc/dc Converters In Thinsot
• Manufacturer: Linear Technology Corporation

TYPICAL PERFOR A CE CHARACTERISTICS
PI FU CTIO S
SW (Pin 1): Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to keep EMI down.
GND (Pin 2): Ground. Tie directly to local ground plane.
NFB (Pin 3): Feedback Pin. Reference voltage is –1.255V.
Connect resistive divider tap here. Minimize trace area.
The NFB bias current flows out of the pin. Set R1 and R2
according to:
5.0
4.0
3.0
7.0
6.5
6.0
5.5
4.5
3.5
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
For LT
U
0
–50
10
Quiescent Current
Current Limit
NOT SWITCHING
20
–25
1931 1
U
30
TEMPERATURE (°C)
:
0
DUTY CYCLE (%)
R
40
=
25
50
U
1 255
LT1931A
.
|
R
LT1931
60
V
2
50
OUT
70
W
+
T
A
| – .
75
(
= 25°C
4 10
80
1931 G04
1931 G01
1 255
•
U
100
90
–
6
)
–1.28
–1.27
–1.26
–1.25
–1.24
–1.23
–1.22
0.30
0.25
0.20
0.10
0.45
0.40
0.35
0.15
0.05
0
–50
0
Feedback Pin Voltage
Switch Saturation Voltage
T
A
= 25°C
–25
0.2
SWITCH CURRENT (A)
TEMPERATURE (°C)
0.4
0
0.6
25
SHDN (Pin 4): Shutdown Pin. Tie to 2.4V or more to enable
device. Ground to shut down.
V
IN
For LT
(Pin 5): Input Supply Pin. Must be locally bypassed.
0.8
50
1.0
75
1931
1931 G05
1931 G02
100
1.2
A R
:
1
=
–10
2.5
2.3
2.1
1.9
1.7
1.5
1.3
1.1
0.9
0.7
0.5
1 255
90
80
70
60
50
40
30
20
10
0
.
–50
|
R
0
Oscillator Frequency
Shutdown Pin Current
V
2
T
A
OUT
LT1931/LT1931A
= 25°C
–25
+
1
| – .
(
8 10
SHDN PIN VOLTAGE (V)
TEMPERATURE (°C)
1 255
•
0
2
–
25
6
3
)
LT1931A
LT1931A
50
4
LT1931
LT1931
75
5
1931 G06
1931 G03
1931fa
3
100
6