1
LT1111
33 F
SUMIDA
CD54-220M
22
H
LT1111 TA01
MBRS120T3
5V
100mA
GND
SW2
SW1
LIM
I
IN
V
LT1111CS8-5
SENSE
3V INPUT
10 F*
+
*OPTIONAL
+
Micropower
DC/DC Converter
Adjustable and Fixed 5V, 12V
All Surface Mount 3V to 5V Step-Up Converter
D
U
ESCRIPTIO
S
FEATURE
U
S
A
O
PPLICATI
Typical Load Regulation
0
LOAD CURRENT (mA)
0
1
OUTPUT VOLTAGE (V)
2
3
4
5
6
50
100
150
200
LT1111 TA02
25
75
125
175
V
IN
= 2V 2.2 2.4 2.6 2.8 3V
s
Operates at Supply Voltages from 2V to 30V
s
72kHz Oscillator
s
Works with Surface Mount Inductors
s
Only Three External Components Required
s
Step-Up or Step-Down Mode
s
Low-Battery Detector Comparator On-Chip
s
User Adjustable Current Limit
s
Internal 1A Power Switch
s
Fixed or Adjustable Output Voltage Versions
s
Space Saving 8-Pin MiniDIP or SO-8 Package
s
3V to 5V, 5V to 12V Converters
s
9V to 5V, 12V to 5V Converters
s
Remote Controls
s
Peripherals and Add-On Cards
s
Battery Backup Supplies
s
Uninterruptible Supplies
s
Laptop and Palmtop Computers
s
Cellular Telephones
s
Portable Instruments
s
Flash Memory VPP Generators
U
A
O
PPLICATI
TYPICAL
The LT1111 is a versatile micropower DC/DC converter.
The device requires only three external components to
deliver a fixed output of 5V or 12V. Supply voltage ranges
from 2V to 12V in step-up mode and to 30V in step-down
mode. The LT1111 functions equally well in step-up, step-
down, or inverting applications.
The LT1111 oscillator is set at 72kHz, optimizing the
device to work with off-the-shelf surface mount inductors.
The device can deliver 5V at 100mA from a 3V input in
step-up mode or 5V at 200mA from a 12V input in step-
down mode.
Switch current limit can be programmed with a single
resistor. An auxiliary open-collector gain block can be
configured as a low-battery detector, linear post regulator,
undervoltage lock-out circuit, or error amplifier.
For input sources of less than 2V use the LT1110.
2
LT1111
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
Operating Temperature Range
LT1111C ............................................... 0
C to 70
C
LT1111I ......................................... 40
C to 105
C
LT1111M ....................................... 55
C to 125
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec) ................. 300
C
W
U
U
PACKAGE/ORDER I FOR ATIO
Supply Voltage (V
IN
) ............................................... 36V
SW1 Pin Voltage (V
SW1
) ......................................... 50V
SW2 Pin Voltage (V
SW2
) ............................ 0.5V to V
IN
Feedback Pin Voltage (LT1111) ............................. 5.5V
Switch Current ....................................................... 1.5A
Maximum Power Dissipation ............................ 500mW
T
JMAX
= 150
C,
JA
= 120
C/W (J)
T
JMAX
= 90
C,
JA
= 130
C/W (N)
ORDER PART
NUMBER
LT1111CN8
LT1111CN8-5
LT1111CN8-12
LT1111MJ8
LT1111MJ8-5
LT1111MJ8-12
1
2
3
4
8
7
6
5
TOP VIEW
I
LIM
V
IN
SW1
SW2
FB (SENSE)*
SET
A0
GND
N8 PACKAGE
8-LEAD PLASTIC DIP
*FIXED VERSIONS
J8 PACKAGE
8-LEAD CERAMIC DIP
LT1111CS8
LT1111CS8-5
LT1111CS8-12
T
JMAX
= 90
C,
JA
= 150
C/W
ORDER PART
NUMBER
1111
11115
11111
S8 PART MARKING
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Q
Quiescent Current
Switch OFF
300
400
A
V
IN
Input Voltage
Step-Up Mode
q
2.0
12.6
V
Step-Down Mode
q
30.0
V
Comparator Trip Point Voltage
LT1111 (Note 1)
q
1.20
1.25
1.30
V
V
OUT
Output Sense Voltage
LT1111-5 (Note 2)
q
4.75
5.00
5.25
V
LT1111-12 (Note 2)
q
11.40
12.00
12.60
V
Comparator Hysteresis
LT1111
q
8
12.5
mV
Output Hysteresis
LT1111-5
q
32
50
mV
LT1111-12
q
75
120
mV
f
OSC
Oscillator Frequency
54
72
88
kHz
DC
Duty Cycle: Step-Up Mode
Full Load
43
50
59
%
Step-Down Mode
24
34
50
%
t
ON
Switch ON Time: Step-Up Mode
I
LIM
Tied to V
IN
5
7
9
s
Step-Down Mode
V
OUT
, = 5V, V
IN
= 12V
3.3
5
7.8
s
V
SAT
SW Saturation Voltage, Step-Up Mode
V
IN
= 3.0V, I
SW
= 650mA
0.5
0.65
V
V
IN
= 5.0V, I
SW
= 1A
0.8
1.0
V
SW Saturation Voltage, Step-Down Mode
V
IN
= 12V, I
SW
= 650mA
1.1
1.5
V
I
FB
Feedback Pin Bias Current
LT1111, V
FB
= 0V
q
70
120
nA
I
SET
Set Pin Bias Current
V
SET
= V
REF
q
70
300
nA
V
OL
Gain Block Output Low
I
SINK
= 300
A, V
SET
= 1.00V
q
0.15
0.4
V
ELECTRICAL C
C
HARA TERISTICS
V
IN
= 3V, Military or Commercial Version
Consult factory for Industrial grade parts
1
2
3
4
8
7
6
5
TOP VIEW
FB (SENSE)*
SET
A0
GND
I
LIM
V
IN
SW1
SW2
S8 PACKAGE
8-LEAD PLASTIC SO
*FIXED VERSION
3
LT1111
ELECTRICAL C
C
HARA TERISTICS
V
IN
= 3V, Military or Commercial Version
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reference Line Regulation
5V
V
IN
30V
q
0.02
0.075
%/V
2V
V
IN
5V
0.20
0.400
%/V
A
V
Gain Block Gain
R
L
= 100k (Note 3)
q
1000
6000
V/V
I
LIM
Current Limit
220
from I
LIM
to V
IN
400
mA
Current Limit Temperature Coefficient
q
0.3
%/
C
Switch OFF Leakage Current
Measured at SW1 Pin, V
SW1
= 12V
1
10
A
Maximum Excursion Below GND
I
SW1
10
A, Switch OFF
400
350
mV
LT1111M
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Q
Quiescent Current
Switch OFF
q
300
500
A
f
OSC
Oscillator Frequency
q
45
72
100
kHz
DC
Duty Cycle: Step-Up Mode
Full Load
q
40
50
62
%
Step-Down Mode
q
20
55
%
t
ON
Switch ON Time: Step-Up Mode
I
LIM
Tied to V
IN
q
5
7
11
s
Step-Down Mode
V
OUT
= 5V, V
IN
= 12V
q
3
9
s
Reference Line Regulation
2V
V
IN
5V, 25
C
T
A
125
C
0.2
0.4
%/V
2.4V
V
IN
5V, T
A
= 55
C
0.8
%/V
V
SAT
SW Saturation Voltage, Step-Up Mode
0
C
T
A
125
C, I
SW
= 500mA,
0.5
0.65
V
T
A
= 55
C, I
SW
= 400mA
SW Saturation Voltage, Step-Down Mode
V
IN
= 12V, 0
C
T
A
125
C
1.5
V
I
SW
= 500mA T
A
= 55
C
2.0
V
V
IN
= 3V, 55
C
T
A
125
C unless otherwise noted.
LT1111C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Q
Quiescent Current
Switch OFF
q
300
450
A
f
OSC
Oscillator Frequency
q
54
72
95
kH
DC
Duty Cycle: Step-Up Mode
Full Load
q
43
50
59
%
Step-Down Mode
q
24
34
50
%
t
ON
Switch ON Time: Step-Up Mode
I
LIM
Tied to V
IN
q
5.0
7
9.0
s
Step-Down Mode
V
OUT
= 5V, V
IN
= 12V
q
3.3
5
7.8
s
Reference Line Regulation
2V
V
IN
5V
q
0.2
0.7
%/V
V
SAT
SW Saturation Voltage, Step-Up Mode
V
IN
= 3V, I
SW
= 650mA
q
0.5
0.65
V
SW Saturation Voltage, Step-Down Mode
V
IN
= 12V, I
SW
= 650mA
q
1.1
1.50
V
V
IN
= 3V, 0
C
T
A
70
C unless otherwise noted.
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1: This specification guarantees that both the high and low trip points
of the comparator fall within the 1.20V to 1.30V range.
Note 2: The output voltage waveform will exhibit a sawtooth shape due to
the comparator hysteresis. The output voltage on the fixed output versions
will always be within the specified range.
Note 3: 100k resistor connected between a 5V source and the A0 pin.
4
LT1111
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
TEMPERATURE (
C)
ON TIME (
s)
50
25
0
25
LT111 TPC03
50
75
100
125
10
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
Oscillator Frequency
Oscillator Frequency
Switch ON Time
TEMPERATURE (
C)
50
40
OSCILLATOR FREQUENCY (KHz)
50
60
70
80
90
100
25
0
25
50
LT1111 TPC01
75
100
125
INPUT VOLTAGE (V)
0
69
FREQUENCY (KHz)
70
71
72
73
74
75
3
6
9
12
LT1111 TPC02
15 18 21
68
67
24 27 30
Saturation Voltage
Saturation Voltage
Duty Cycle
Step-Up Mode
Step-Up Mode
TEMPERATURE (
C)
DUTY CYCLE (%)
50
25
0
25
LT1111 TPC04
50
75
100
125
60
58
56
54
52
50
48
46
44
42
40
SWITCH CURRENT (A)
SATURATION VOLTAGE (V)
0
0.2
0.4
0.6
LT1111 TPC06
0.8
1.0
1.2
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.4
V
IN
= 3V
V
IN
= 2V
V
IN
= 5V
TEMPERATURE (
C)
SATURATION VOLTAGE (V)
50
25
0
25
LT1111 TPC05
50
75
100
125
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
V
IN
= 3V
I
SW =
650mA
Switch ON Voltage
Switch ON Voltage
Minimum/Maximum Frequency
Step-Down Mode
Step-Down Mode
vs ON Time
SWITCH CURRENT (A)
ON VOLTAGE (V)
0
0.2
0.4
0.6
LT1111 TPC08
0.8
1.0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
IN
= 12V
TEMPERATURE (
C)
ON VOLTAGE (V)
50
25
0
25
LT1111 TPC07
50
75
100
2.00
1.75
1.50
1.25
1.00
0.75
0.50
125
V
IN
= 12V
I
SW =
650mA
SWITCH ON TIME (
s)
OSCILLATOR FREQUENCY (KHz)
4
5
6
7
LT1111 TPC09
8
9
100
90
80
70
60
50
40
10
11
12
55
C
T
A
125
C
0
C
T
A
70
C
5
LT1111
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
GND (Pin 5): Ground.
A0 (Pin 6): Auxiliary Gain Block (GB) Output. Open collector,
can sink 300
A.
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 (
A)
0
LT1111 TPC10
3
400
380
360
340
320
280
260
6
240
220
200
300
9
12 15 18 21 24 27
30
TEMPERATURE (
C)
QUIESCENT CURRENT (
A)
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 220
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
(
)
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
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