Datasheet

5
L T 1111
1111fd
CCHARA TERIST
ICS
UW
AT
Y
P
I
CA
LPER
F
O
R
C
E
GND (Pin 5): Ground.
A0 (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 LT1111 (adjustable) this pin
goes to the comparator input. On the LT1111-5 and
LT1111-12, this pin goes to the internal application resistor
that sets output voltage.
Maximum Switch Current
Quiescent Current Quiescent Current vs R
LIM
INPUT VOLTAGE (V)
QUIESCENT CURRENT (µA)
0
LT1111 • TPC10
3
400
380
360
340
320
280
260
6
240
220
200
300
912151821242730
TEMPERATURE (°C)
QUIESCENT CURRENT (µA)
–50
LT1111 • TPC11
500
450
400
350
250
–25
150
100
200
300
0 25 50 75 100 125
TEMPERATURE (°C)
BIAS CURRENT (nA)
–50
LT1111 • TPC14
100
90
80
70
50
–25
30
20
40
60
0 25 50 75 100 125
10
0
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.
PI
U
FU
U
C
U
S
O
TI
TEMPERATURE (°C)
BIAS CURRENT (nA)
–50
LT1111 • TPC13
100
90
80
70
50
–25
30
20
40
60
0 25 50 75 100 125
10
0
Set Pin Bias Current Feedback Bias Current
R
LIM
(Ω)
SWITCH CURRENT (A)
10
LT1111 • TPC12
100
1.5
1.4
1.3
1.2
1.1
0.9
0.8
1000
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1.0
STEP-DOWN
V
IN
= 12V
STEP-UP
2V ≤ V
IN
≤ 5V