LT1110
Micropower
DC-DC Converter
Adjustable and Fixed 5V, 12V
FEATURES
s
s
s
DESCRIPTIO
s
s
s
s
s
Operates at Supply Voltages From 1.0V to 30V
Works in Step-Up or Step-Down Mode
Only Three External Off-the-Shelf Components
Required
Low-Battery Detector Comparator On-Chip
User-Adjustable Current Limit
Internal 1A Power Switch
Fixed or Adjustable Output Voltage Versions
Space-Saving 8-Pin MiniDIP or S8 Package
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 300µA, 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.
APPLICATI
s
s
s
s
s
s
s
s
s
S
Pagers
Cameras
Single-Cell to 5V Converters
Battery Backup Supplies
Laptop and Palmtop Computers
Cellular Telephones
Portable Instruments
Laser Diode Drivers
Hand-Held Inventory Computers
TYPICAL APPLICATI
All Surface Mount
Single Cell to 5V Converter
SUMIDA
CD54-470K
47µH
1
I
LIM
1.5V
AA CELL*
2
V
IN
SW1
90
MBRS120T3
5V
EFFICIENCY (%)
85
80
75
70
65
60
15µF
TANTALUM
55
50
0
LT1110 • TA01
3
V
IN
= 1.00V
LT1110-5
SENSE
8
SW2
4
GND
5
+
OPERATES WITH CELL VOLTAGE
≥
1.0V
*ADD 10
µ
F DECOUPLING CAPACITOR IF BATTERY
IS MORE THAN 2" AWAY FROM LT1110.
5
10
U
Efficiency
V
IN
= 1.50V
V
IN
= 1.25V
15
20
25
30
35
40
LOAD CURRENT (mA)
LT1110 • TA02
UO
UO
1
LT1110
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
I
LIM
1
V
IN
2
SW1 3
SW2 4
8
7
6
5
FB (SENSE)*
SET
A0
GND
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
N8 PACKAGE
8-LEAD PLASTIC DIP
*FIXED VERSIONS
T
JMAX
= 90°C,
θ
JA
= 130°C/W
TOP VIEW
I
LIM
1
V
IN
2
SW1 3
SW2 4
8
7
6
5
FB (SENSE)*
SET
A0
GND
LT1110CS8
LT1110CS8-5
LT1110CS8-12
S8 PART MARKING
1110
11105
11012
S8 PACKAGE
8-LEAD PLASTIC SOIC
*FIXED VERSIONS
T
JMAX
= 90°C,
θ
JA
= 150°C/W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
T
A
= 25°C, V
IN
= 1.5V, unless otherwise noted.
SYMBOL
I
Q
V
IN
PARAMETER
Quiescent Current
Input Voltage
CONDITIONS
Switch Off
Step-Up Mode
Step-Down Mode
Comparator Trip Point Voltage
V
OUT
Output Sense Voltage
Comparator Hysteresis
Output Hysteresis
f
OSC
DC
t
ON
I
FB
I
SET
V
AO
Oscillator Frequency
Duty Cycle
Switch ON Time
Feedback Pin Bias Current
Set Pin Bias Current
AO Output Low
Reference Line Regulation
LT1110, V
FB
= 0V
V
SET
= V
REF
I
AO
=
–300µA, V
SET
= 150mV
1.0V
≤
V
IN
≤
1.5V
1.5V
≤
V
IN
≤
12V
Full Load (V
FB
<
V
REF
)
LT1110 (Note 1)
LT1110-5 (Note 2)
LT1110-12 (Note 2)
LT1110
LT1110-5
LT1110-12
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
MIN
1.15
1.0
210
4.75
11.4
TYP
300
MAX
12.6
12.6
30
UNITS
µA
V
V
V
mV
V
V
mV
mV
mV
kHz
%
µs
nA
nA
V
%/V
%/V
220
5.00
12.00
4
90
200
230
5.25
12.6
8
180
400
90
78
12.5
150
300
0.4
1.0
0.1
52
62
7.5
70
69
10
70
100
0.15
0.35
0.05
2
U
W
U
U
W W
W
LT1110
ELECTRICAL CHARACTERISTICS
T
A
= 25°C, V
IN
= 1.5V, unless otherwise noted.
SYMBOL
V
CESAT
PARAMETER
Switch Saturation Voltage
Step-Up Mode
CONDITIONS
V
IN
= 1.5V, I
SW
= 400mA
q
MIN
TYP
300
400
MAX
400
600
550
750
1000
UNITS
mV
mV
mV
mV
mV
V/V
mA
mA
%/°C
V
IN
= 1.5V, I
SW
= 500mA
q
V
IN
= 5V, I
SW
= 1A
A
V
I
REV
I
LIM
A2 Error Amp Gain
Reverse Battery Current
Current Limit
Current Limit Temperature
Coefficient
I
LEAK
V
SW2
Switch OFF Leakage Current
Maximum Excursion Below GND
Measured at SW1 Pin
I
SW1
≤
10µA, Switch Off
R
L
= 100kΩ (Note 3)
(Note 4)
220Ω Between I
LIM
and V
IN
q
700
1000
5000
750
400
– 0.3
1
– 400
10
– 350
µA
mV
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.
Note 3:
100kΩ 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.
TYPICAL PERFOR A CE CHARACTERISTICS
Oscillator Frequency
100
OSCILLATOR FREQUENCY (KHz)
80
78
90
80
70
60
50
40
–50
FREQUENCY (KHz)
72
70
68
66
64
62
60
ON TIME (µs)
3
6
12 15 18 21 24 27 30
LT1110 • TPC02
–25
0
25
50
TEMPERATURE (°C)
LT1110 • TPC01
U W
75
Oscillator Frequency
14
13
12
11
10
9
8
Switch On Time
76
74
100
0
9
7
–50
–25
0
25
50
75
100
INPUT VOLTAGE (V)
TEMPERATURE (°C)
LT1110 • TPC03
3
LT1110
TYPICAL PERFOR A CE CHARACTERISTICS
Duty Cycle
78
76
74
500
450
400
350
V
CESAT
(mV)
V
CESAT
(V)
DUTY CYCLE (%)
72
70
68
66
64
62
60
58
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
LT1110 • TPC04
Switch On Voltage
Step-Down Mode
1.4
V
IN
= 12V
1.2
1.0
100
95
90
85
80
75
70
65
60
55
50
45
40
OSCILLATOR FREQUENCY (KHz)
QUIESCENT CURRENT (µA)
ON VOLTAGE (V)
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1.0
I
SWITCH
(A)
LT1110 • TPC07
Quiescent Current
500
450
QUIESCENT CURRENT (µA)
SWITCH CURRENT (A)
1.5
1.3
1.1
0.9
0.7
0.5
0.3
0.1
SWITCH CURRENT (A)
400
350
300
250
200
150
100
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
LT1110 • TPC10
4
U W
Switch Saturation Voltage
1.4
V
IN
= 1.5V
I
SW
= 500mA
Saturation Voltage
Step-Up Mode
V
IN
= 3.0V
V
IN
= 2.0V
V
IN
= 1.5V
1.2
1.0
0.8
V = 1.2V
IN
0.6
0.4
0.2
0
V
IN
= 1.0V
V
IN
= 5.0V
300
250
200
150
100
50
0
–50
– 25
0
25
50
75
100
0
0.2
0.4
0.6
0.8 1.0
1.2
1.4
1.6
TEMPERATURE (°C)
LT1110 • TPC05
I
SWITCH
(A)
LT1110 • TPC06
Minimum/Maximum Frequency vs
On Time
400
380
360
340
320
300
280
260
240
220
200
Quiescent Current
0°C
≤
T
A
≤
70°C
7
8
9
10
11
12
13
0
3
6
9
12 15 18 21 24 27 30
LT1110 • TPC09
SWITCH ON TIME (µs)
LT1110 • TPC08
INPUT VOLTAGE (V)
Maximum Switch Current vs
R
LIM
Step-Up
1.5
1.3
1.1
0.9
0.7
0.5
0.3
0.1
Maximum Switch Current vs
R
LIM
Step-Down
STEP-UP MODE
V
IN
≤
5V
STEP-DOWN MODE
V
IN
= 12V
10
100
R
LIM
(Ω)
1000
LT1110 • TPC11
10
100
R
LIM
(Ω)
1000
LT1110 • TPC12
LT1110
TYPICAL PERFOR A CE CHARACTERISTICS
160
140
120
BIAS CURRENT (nA)
BIAS CURRENT (nA)
Set Pin Bias Current
80
60
40
20
0
–50
–25
0
25
50
75
100
70
60
50
40
30
20
10
0
–50
V
REF
(mV)
–25
100
TEMPERATURE (°C)
LT1110 • TPC13
PI FU CTI
S
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
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.
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.
LT1110 BLOCK DIAGRA
V
IN
220mV
REFERENCE
A1
COMPARATOR
GND
FB
OSCILLATOR
DRIVER
SW2
LT1110 • BD01
W
U W
120
110
100
90
80
FB Pin Bias Current
226
224
222
220
218
216
214
Reference Voltage
0
25
50
75
100
212
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
LT1110 • TPC14
TEMPERATURE (°C)
LT1110 • TPC15
UO
U
U
SET
+
A2
AO
GAIN BLOCK/ERROR AMP
I
LIM
SW1
–
Q1
5
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