Datasheet
5
LT1107
1107fa
I
LIM
(Pin 1): Connect this pin to V
IN
for normal use. Where
lower current limit is desired, connect a resistor between
I
LIM
and V
IN
. A 220Ω resistor will limit the switch current
to approximately 400mA.
V
IN
(Pin 2): Input Supply Voltage.
SW1 (Pin 3):
Collector of Power Transistor. For step-up
mode connect to inductor/diode. For step-down mode
connect to V
IN
.
SW2 (Pin 4):
Emitter of Power Transistor. For step-up
mode connect to ground. For step-down mode connect to
inductor/diode. This pin must never be allowed to go more
than a Schottky diode drop below ground.
GND (Pin 5): Ground.
AO (Pin 6): Auxiliary Gain Block (GB) Output. Open collector,
can sink 300µA.
SET (Pin 7): GB Input. GB is an op amp with positive input
connected to SET pin and negative input connected to
1.25V reference.
FB/SENSE (Pin 8): On the LT1107 (adjustable), this pin
goes to the comparator input. On the LT1107-5 and
LT1107-12, this pin goes to the internal application resistor
that sets output voltage.
PI
U
FU
U
C
U
S
O
TI
CCHARA TERIST
ICS
UW
AT
Y
P
I
CA
LPER
F
O
R
C
E
Minimum/Maximum Frequency Minimum/Maximum Frequency
vs ON Time, Step-Down Mode vs ON Time, Step-Up Mode
TEMPERATURE (°C)
–55
DUTY CYCLE (%)
–15
25
45 125
1107 G13
–35 5
65
85
105
70
65
60
55
50
45
40
35
TEMPERATURE (°C)
–55
OUTPUT VOLTAGE (V)
–15
25
45 125
1107 G16
–35 5
65
85
105
5.3
5.2
5.1
5.0
4.9
4.8
4.7
TEMPERATURE (°C)
–55
OUTPUT VOLTAGE (V)
–15
25
45 125
1107 G17
–35 5
65
85
105
12.20
12.15
12.10
12.05
12.00
11.95
11.90
11.85
11.80
LT1107-5 LT1107-12 LT1107
Output Voltage Output Voltage Feedback Voltage
TEMPERATURE (°C)
–55
TRIP POINT VOLTAGE (V)
–15
25
45 125
1107 G18
–35 5
65
85
105
1.30
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.20
ON TIME (µs)
4
FREQUENCY (kHz)
100
90
80
70
60
50
40
30
5
9
11
1107 G11
8
13
14
6
7
10 12
0°C ≤ T
A
≤ 70°C
–55°C ≤ T
A
≤ 125°C
ON TIME (µs)
6
FREQUENCY (kHz)
100
90
80
70
60
50
40
30
7
11
13
1107 G12
10
15
16
8
9
12 14
0°C ≤ T
A
≤ 70°C
–55°C ≤ T
A
≤ 125°C
T
A
= 25°C
Duty Cycle
Step-Down Mode