LT1110
1
D
U
ESCRIPTIO
The LT1110 is a versatile micropower DC-DC converter.
The device requires only three external components to
deliver a fixed output of 5V or 12V. The very low minimum
supply voltage of 1.0V allows the use of the LT1110 in
applications where the primary power source is a single
cell. An on-chip auxiliary gain block can function as a low
battery detector or linear post regulator.
The 70kHz oscillator allows the use of surface mount
inductors and capacitors in many applications. Quiescent
current is just 300
A, making the device ideal in remote or
battery powered applications where current consumption
must be kept to a minimum.
The device can easily be configured as a step-up or
step-down converter, although for most step-down
applications or input sources greater than 3V, the LT1111
is recommended. Switch current limiting is user-adjustable
by adding a single external resistor. Unique reverse battery
protection circuitry limits reverse current to safe, non-
destructive levels at reverse supply voltages up to 1.6V.
S
FEATURE
s
Operates at Supply Voltages From 1.0V to 30V
s
Works in Step-Up or Step-Down Mode
s
Only Three External Off-the-Shelf Components
Required
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 S8 Package
U
S
A
O
PPLICATI
s
Pagers
s
Cameras
s
Single-Cell to 5V Converters
s
Battery Backup Supplies
s
Laptop and Palmtop Computers
s
Cellular Telephones
s
Portable Instruments
s
Laser Diode Drivers
s
Hand-Held Inventory Computers
Micropower
DC-DC Converter
Adjustable and Fixed 5V, 12V
LOAD CURRENT (mA)
0
EFFICIENCY (%)
50
60
70
80
85
90
10
20
30
40
LT1110 TA02
75
65
55
5
15
25
35
V
IN
= 1.50V
V
IN
= 1.25V
V
IN
= 1.00V
U
A
O
PPLICATI
TYPICAL
Efficiency
All Surface Mount
Single Cell to 5V Converter
LT1110 TA01
+
GND
SW2
SENSE
SW1
LIM
I
IN
V
5
4
1
3
8
LT1110-5
1.5V
AA CELL*
*ADD 10 F DECOUPLING CAPACITOR IF BATTERY
IS MORE THAN 2" AWAY FROM LT1110.
15
F
TANTALUM
5V
MBRS120T3
SUMIDA
CD54-470K
47
H
OPERATES WITH CELL VOLTAGE 1.0V
2
LT1110
2
W
U
U
PACKAGE/ORDER I FOR ATIO
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
Supply Voltage, Step-Up Mode ................................ 15V
Supply Voltage, Step-Down Mode ........................... 36V
SW1 Pin Voltage ...................................................... 50V
SW2 Pin Voltage ......................................... 0.5V to V
IN
Feedback Pin Voltage (LT1110) .............................. 5.5V
Switch Current ........................................................ 1.5A
Maximum Power Dissipation ............................. 500mW
Operating Temperature Range ..................... 0
C to 70
C
Storage Temperature Range .................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec.)................. 300
C
ORDER PART
NUMBER
LT1110CN8
LT1110CN8-5
LT1110CN8-12
1110
11105
11012
Consult factory for Industrial and Military grade parts.
T
JMAX
= 90
C,
JA
= 150
C/W
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
T
JMAX
= 90
C,
JA
= 130
C/W
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 SOIC
*FIXED VERSIONS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Q
Quiescent Current
Switch Off
q
300
A
V
IN
Input Voltage
Step-Up Mode
q
1.15
12.6
V
1.0
12.6
V
Step-Down Mode
q
30
V
Comparator Trip Point Voltage
LT1110 (Note 1)
q
210
220
230
mV
V
OUT
Output Sense Voltage
LT1110-5 (Note 2)
q
4.75
5.00
5.25
V
LT1110-12 (Note 2)
q
11.4
12.00
12.6
V
Comparator Hysteresis
LT1110
q
4
8
mV
Output Hysteresis
LT1110-5
q
90
180
mV
LT1110-12
q
200
400
mV
f
OSC
Oscillator Frequency
q
52
70
90
kHz
DC
Duty Cycle
Full Load (V
FB
<
V
REF
)
q
62
69
78
%
t
ON
Switch ON Time
q
7.5
10
12.5
s
I
FB
Feedback Pin Bias Current
LT1110, V
FB
= 0V
q
70
150
nA
I
SET
Set Pin Bias Current
V
SET
= V
REF
q
100
300
nA
V
AO
AO Output Low
I
AO
=
300
A, V
SET
= 150mV
q
0.15
0.4
V
Reference Line Regulation
1.0V
V
IN
1.5V
q
0.35
1.0
%/V
1.5V
V
IN
12V
q
0.05
0.1
%/V
ELECTRICAL C
C
HARA TERISTICS
T
A
= 25
C, V
IN
= 1.5V, unless otherwise noted.
S8 PART MARKING
LT1110CS8
LT1110CS8-5
LT1110CS8-12
LT1110
3
V
CESAT
Switch Saturation Voltage
V
IN
= 1.5V, I
SW
= 400mA
300
400
mV
Step-Up Mode
q
600
mV
V
IN
= 1.5V, I
SW
= 500mA
400
550
mV
q
750
mV
V
IN
= 5V, I
SW
= 1A
700
1000
mV
A
V
A2 Error Amp Gain
R
L
= 100k
(Note 3)
q
1000
5000
V/V
I
REV
Reverse Battery Current
(Note 4)
750
mA
I
LIM
Current Limit
220
Between I
LIM
and V
IN
400
mA
Current Limit Temperature
0.3
%/
C
Coefficient
I
LEAK
Switch OFF Leakage Current
Measured at SW1 Pin
1
10
A
V
SW2
Maximum Excursion Below GND
I
SW1
10
A, Switch Off
400
350
mV
ELECTRICAL C
C
HARA TERISTICS
T
A
= 25
C, V
IN
= 1.5V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Note 3: 100k
resistor connected between a 5V source and the AO pin.
Note 4: The LT1110 is guaranteed to withstand continuous application of
+1.6V applied to the GND and SW2 pins while V
IN
, I
LIM
, and SW1 pins are
grounded.
The
q
denotes the specifications which apply over the full operating
temperature range.
Note 1: This specification guarantees that both the high and low trip point
of the comparator fall within the 210mV to 230mV range.
Note 2: This specification guarantees that the output voltage of the fixed
versions will always fall within the specified range. The waveform at the
sense pin will exhibit a sawtooth shape due to the comparator hysteresis.
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Oscillator Frequency
Oscillator Frequency
Switch On Time
INPUT VOLTAGE (V)
0
64
FREQUENCY (KHz)
66
70
72
74
78
80
3
6
9
12
LT1110 TPC02
15 18 21
62
60
24 27 30
68
76
TEMPERATURE (
C)
ON TIME (
s)
50
25
0
25
LT1110 TPC03
50
75
100
14
13
12
11
10
9
8
7
TEMPERATURE (
C)
50
40
OSCILLATOR FREQUENCY (KHz)
50
60
70
80
90
100
25
0
25
50
LT1110 TPC01
75
100
LT1110
4
I
SWITCH
(A)
ON VOLTAGE (V)
0
0.2
0.4
0.6
LT1110 TPC07
0.8
1.0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
IN
= 12V
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Saturation Voltage
Duty Cycle
Switch Saturation Voltage
Step-Up Mode
Switch On Voltage
Minimum/Maximum Frequency vs
Step-Down Mode
On Time
Quiescent Current
Maximum Switch Current vs
Maximum Switch Current vs
Quiescent Current
R
LIM
Step-Up
R
LIM
Step-Down
TEMPERATURE (
C)
DUTY CYCLE (%)
50
25
0
25
LT1110 TPC04
50
75
100
78
76
74
72
70
68
66
64
62
60
58
TEMPERATURE (
C)
V
CESAT
(mV)
50
25
0
25
LT1110 TPC05
50
75
100
500
450
400
350
300
250
200
150
100
50
0
V
IN
= 1.5V
I
SW
= 500mA
I (A)
0
0
V (V)
0.2
0.4
0.6
1.2
1.4
0.2
0.4
0.8
1.2
LT1110 TPC06
1.0
1.4
1.6
SWITCH
CESAT
V
IN
= 1.0V
V = 1.2V
IN
V
IN
= 1.5V
V
IN
= 5.0V
V = 2.0V
IN
0.6
1.0
0.8
V
IN
= 3.0V
INPUT VOLTAGE (V)
QUIESCENT CURRENT (
A)
0
LT1110 TPC09
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
LT1110 TPC10
500
450
400
350
250
25
150
100
200
300
0
25
50
75
100
R
LIM
(
)
SWITCH CURRENT (A)
10
LT1110 TPC11
100
1.5
1.3
1.1
0.9
1000
0.7
0.5
0.3
0.1
STEP-UP MODE
V
IN
5V
R
LIM
(
)
SWITCH CURRENT (A)
10
LT1110 TPC12
100
1.5
1.3
1.1
0.9
1000
0.7
0.5
0.3
0.1
STEP-DOWN MODE
V
IN
= 12V
SWITCH ON TIME (
s)
OSCILLATOR FREQUENCY (KHz)
7
9
LT1110 TPC08
10
100
90
80
70
60
50
40
13
0
C
T
A
70
C
8
11
12
95
85
75
65
55
45
LT1110
5
W
I
D AGRA
BLOCK
LT1110
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Set Pin Bias Current
FB Pin Bias Current
Reference Voltage
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.
GND (Pin 5): Ground.
AO (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
220mV reference.
FB/SENSE (Pin 8): On the LT1110 (adjustable) this pin
goes to the comparator input. On the LT1110-5 and
LT1110-12, this pin goes to the internal application resistor
that sets output voltage.
PI
U
FU
U
C
U
S
O
TI
TEMPERATURE (
C)
BIAS CURRENT (nA)
50
LT1110 TPC13
160
140
120
100
60
25
20
0
40
80
0
25
50
75
100
TEMPERATURE (
C)
V
REF
(mV)
50
25
0
25
LT1110 TPC15
50
75
100
226
224
222
220
218
216
214
212
TEMPERATURE (
C)
BIAS CURRENT (nA)
50
120
100
90
70
40
25
10
0
30
60
0
25
50
75
100
20
50
80
110
LT1110 TPC14
LT1110 BD01
IN
V
GND
SET
AO
GAIN BLOCK/ERROR AMP
220mV
REFERENCE
A1
A2
DRIVER
+
FB
SW1
SW2
LIM
I
OSCILLATOR
COMPARATOR
Q1
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