LT1120A
Micropower Regulator with
Comparator and Shutdown
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
20µA Supply Current
125mA Output Current
2.5V Reference
Reference Output Sources 4mA and Sinks 4mA
Open Collector Comparator Sinks 10mA
Logic Shutdown
0.2V Dropout Voltage
Thermal Limiting
8-Lead SO Package
The LT
®
1120A is a combination micropower positive
regulator and free collector comparator on a single mono-
lithic chip. With only 20µA supply current, the LT1120A
can supply over 125mA of output current. Input voltage
range is from 4.5V to 36V and dropout voltage is 0.6V at
125mA. Dropout voltage decreases with lower load cur-
rents. Also included on the chip is a class B output 2.5V
reference that can either source or sink current. This
allows it to be used as a supply splitter or auxiliary output.
A shutdown pin allows logic shutdown of the output.
The comparator can be used for system or battery moni-
toring. For example, the comparator can be used to warn
of low system voltage. Frequency compensation of the
comparator for amplifier applications can be obtained by
adding external output capacitance.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
Battery Systems
Battery Backup System
Portable Terminals
Portable Instruments
Memory Keep Alive
TYPICAL APPLICATIO
5V Regulator
Dropout Voltage and Supply Current
1.00
10
LT1120A
0.001µF
FB 2
1M
+
10µF
3
SHUTDOWN
GND
1
+
25µF
1M
1120A TA01
DROPOUT VOLTAGE (V)
V
IN
> 5.2V
I
Q
= 20µA
5 V
IN
V
OUT
4
5V
0.10
0.01
0.1
1
10
100
OUTPUT CURRENT (mA)
U
SUPPLY CURRENT (mA)
1
0.1
1000
1120A TA02
U
U
1120afa
1
LT1
120A
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
GND 1
FEEDBACK 2
SHUTDOWN 3
V
OUT
4
N8 PACKAGE
8-LEAD PDIP
8
7
6
5
–INPUT
COMP OUT
REF
V
IN
Input Voltage ........................................................... 36V
NPN Collector Voltage ............................................. 36V
Output Short-Circuit Duration .......................... Indefinite
Power Dissipation ............................... Internally Limited
Operating Temperature Range
LT1120AC ............................................. 0°C to 100°C
LT1120AI ......................................... – 40°C to 100°C
Storage Temperature Range ................. – 65°C to 150°C
ORDER PART
NUMBER
LT1120ACN8
LT1120ACS8
LT1120AIS8
S8 PART
MARKING
1120A
1120AI
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 110°C,
θ
JA
= 130°C/W (N)
T
JMAX
= 110°C,
θ
JA
= 190°C/W (S)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
PARAMETER
Reference
Reference Voltage
Line Regulation
Load Regulation
Output Source Current
Output Sink Current
Temperature Stability
Regulator
Supply Current
CONDITIONS
T
J
= 25°C
MIN
2.46
TYP
2.50
0.01
0.3
4
4
1
20
30
11
125
0.2
0.01
0.02
0.40
2.5
1.4
10
15
1
250
3
15
10000
96
18
0.4
5
0.5
0.015
0.05
0.65
2.56
0.4
MAX
2.54
0.015
0.6
UNITS
V
%/V
%
mA
mA
%
µA
µA
mA
mA
%
%/V
V
V
V
V
V
µA
nA
µA
mA
mV
nA
V/V
dB
mA
V
V
µs
µA
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4.5V
≤
V
IN
≤
36V
4.5V
≤
V
IN
≤
36V
–2.0mA
≤
I
REF
≤
2mA, V
IN
= 12V
V
IN
= 5V
V
IN
= 5V
2
2
Output Current
Load Regulation
Line Regulation
Dropout Voltage
Feedback Sense Voltage
Shutdown Pin Voltage
Shutdown Pin Current
Feedback Bias Current
Minimum Load Current
Short-Circuit Current
Comparator
Offset Voltage
Bias Current
Gain
Power Supply Rejection
Output Sink Current
Saturation Voltage
Input Voltage Range
Response Time
Leakage Current
V
IN
= 6V, I
OUT
≤
100mA
V
IN
= 36V, I
OUT
≤
100mA
V
IN
= 12V, I
OUT
= 125mA
(V
IN
– V
OUT
)
≥
1V, V
IN
≥
6V
(V
IN
– V
OUT
)
≥
1V, V
IN
≥
6V
6V
≤
V
IN
≤
36V
I
OUT
= 100mA
I
OUT
= 125mA
V
IN
= 12V
Normal
V
OUT
≤
0.5V
Shutdown
V
IN
= 1.4V
V
IN
= 36V
V
IN
= 36V
V
IN
= 36V
V
IN
= 36V
∆V
OUT
= 29V, R
L
= 20k
4.5V
≤
V
S
≤
36V
V
IN
= 4.5V
I
OUT
= 1mA
25
40
20
2.44
2.2
40
5
400
7
40
2000
80
10
0
0.6
V
IN
– 1
2
V
IN
= 36V, V(Pin 7) = 36V
2
U
W
U
U
W W
W
LT1120A
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating temperature range of T
J
= 25°C.
PARAMETER
Reference
Reference Voltage
Line Regulation
Load Regulation
Output Source Current
Output Sink Current
Regulator
Supply Current
CONDITIONS
4.5V
≤
V
IN
≤
36V
4.5V
≤
V
IN
≤
36V
–2.0mA
≤
I
REF
≤
2mA, V
IN
= 12V
V
IN
= 5V
V
IN
= 5V
V
IN
= 6V, I
OUT
≤
100µA
V
IN
= 36V, I
OUT
≤
100µA
V
IN
= 12V, I
OUT
= 125mA
(V
IN
– V
OUT
)
≥
1V, V
IN
≥
6V
(V
IN
– V
OUT
)
≥
1V, V
IN
≥
6V
6V
≤
V
IN
≤
36V
I
OUT
= 100µA
I
OUT
= 125mA
V
IN
= 12V
V
IN
= 36V
V
IN
= 36V
V
IN
= 36V
V
IN
= 36V
∆V
OUT
= 29V, R
L
= 20k
V
IN
= 4.5V
V
IN
= 36V, V(Pin 7) = 36V
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
MIN
2.40
TYP
2.50
0.01
0.4
MAX
2.55
0.02
0.8
UNITS
V
%/V
%
mA
mA
µA
µA
mA
mA
%
%/V
V
V
V
nA
µA
mA
mV
nA
V/V
mA
µA
2
2
30
40
11
125
1
0.02
0.06
0.85
2.57
50
50
400
10
60
40
50
20
Output Current
Load Regulation
Line Regulation
Dropout Voltage
Feedback Sense Voltage
Feedback Bias Current
Minimum Load Current
Short-Circuit Current
Comparator
Offset Voltage
Bias Current
Gain
Output Sink Current (Note 2)
Leakage Current
2.38
2.5
240
15
1000
5
10
8
Note 1:
Absolute Maximum Ratings are those values beyond which the life
to the device may be impaired.
Note 2:
For T
A
≤
–40°C output sink current drops to 2.5mA.
TYPICAL PERFOR A CE CHARACTERISTICS
Regulator Load Regulation
0.3
PRE-LOAD = 100µA
T
J
= –55°C
100
SUPPLY CURRENT (mA)
T
J
= 25°C
0.1
0
T
J
= 125°C
–0.1
–0.2
–0.3
0.1
10
SHORT-CIRCUIT CURRENT (mA)
OUTPUT VOLTAGE CHANGE (%)
0.2
1
100
10
OUTPUT CURRENT (mA)
U W
1120A G01
Supply Current
350
300
250
200
150
100
50
Regulator Short-Circuit Current
1
0.1
1000
0.01
0.1
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
1120A G02
0
–50
–10
30
70
110
TEMPERATURE (°C)
150
1120A G03
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LT1
120A
TYPICAL PERFOR A CE CHARACTERISTICS
Dropout Voltage
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
1
∆V
OUT
= 100mV
MINIMUM LOAD CURRENT (µA)
RIPPLE REJECTION (dB)
0.1
0.01
0.1
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
1120A G04
Supply Current
10
I
OUT
= 100mA
SUPPLY CURRENT (mA)
1
SUPPLY CURRENT (mA)
REFERENCE VOLTAGE CHANGE (mV)
0.1
I
OUT
= 10mA
I
OUT
= 1mA
0.01
V
OUT
= 5V
0.01
1
5
20
15
10
25
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
1120A G07
OUTPUT VOLTAGE CHANGE (%)
Feedback Pin Current
40
35
FEEDBACK PIN CURRENT (nA)
25
20
15
10
5
0
0.1
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
1120A G10
OUTPUT VOLTAGE (V)
30
T
J
= –55°C
OUTPUT CURRENT (mA)
T
J
= 25°C
T
J
= 125°C
4
U W
Regulator Minimum Load Current
100
70
65
60
55
50
45
40
35
Regulator Ripple Rejection
I
OUT
= 100mA
10
I
OUT
= 10mA
I
OUT
= 1mA
V
IN
= 10VDC,
1V
P-P
V
OUT
= 5V
C
OUT
= 10µF
10
100
1k
10k
RIPPLE FREQUENCY (Hz)
100k
1120A G06
1
70
80
90
100 110 120 130 140 150
TEMPERATURE (°C)
1120A G05
30
Supply Current at Dropout
10
I
OUT
= 100mA
1
4
3
2
1
0
–1
–2
–3
Reference Regulation
0.1
I
OUT
= 10mA
I
OUT
= 1mA
0
0.1
0.5
0.3
0.4
0.2
0.6
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
1120A G08
–4
–1.5
–1.0 –0.5
0.5
1.0
0
REFERENCE OUTPUT CURRENT (mA)
1.5
1120A G09
Regulator Thermal Regulation
0.1
V
IN
= 15V
V
OUT
= 5V
0
Turn-On Characteristic
5.5
V
OUT
= 5V
5.0
NO LOAD
4.5
4.0
R
L
= 500Ω
3.5
3.0
2.5
2.0
R
L
= 50Ω
0
1
2
3
4
5
6
INPUT VOLTAGE (V)
7
8
–0.1
50
0
0
20 40 60 80 100 120 140 160 180
TIME (ms)
1120A G11
0
1120A G12
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LT1120A
PI FU CTIO S
GND (Pin 1):
Ground
FEEDBACK (Pin 2):
This is the feedback point of the
regulator. When operating, it is nominally at 2.5V.
Optimum source resistance is 200k to 500k. The feedback
pin should not be driven below ground or more positive
than 5V.
SHUTDOWN (Pin 3):
A logic 1 shuts off main regulator.
Caution: noise or leakage into the shutdown pin can affect
output voltage.
V
OUT
(Pin 4):
Main output, requires 10µF output capaci-
tor. Can be shorted to V
IN
or ground without damaging
device.
V
IN
(Pin 5):
Input Supply. Bypass with 10µF capacitor.
Must always be more positive than ground.
REF (Pin 6):
Reference. 2.5V can source or sink current.
May be shorted to ground or up to 5V. Voltages in excess
of 5V can damage the device.
COMP OUT (Pin 7):
Open Collector NPN Output. May be
connected to any voltage from ground to 36V more
positive than ground (operates above V
IN
). Short-circuit
protected.
–INPUT (Pin 8):
Inverting Comparator Input.
BLOCK DIAGRA
APPLICATIO S I FOR ATIO
The LT1120A is especially suited for micropower system
applications. For example, the comparator section of the
LT1120A may be used as a battery checker to provide an
indication of low battery. Another type of system applica-
tion for the LT1120A would be to generate the equivalent
of split supplies off of a single power input. The regulator
section provides regulated output voltage and the
reference, which can both source and sink current is then
an artificial system ground providing a split supply for
the system.
U
W
W
U U
U
U
U
REF
6
V
IN
5
+
COMP OUT
7
100k
–
REF
2.5V
120k
3 SHUTDOWN
1 GROUND
8
–INPUT
4 V
OUT
2 FEEDBACK
1120A BD01
For many applications the comparator can be frequency
compensated to operate as an amplifier. Compensation
values for various gains are given in the data sheet. The
comparator gain is purposely low to make it easier to
frequency compensate as an amplifier. The NPN output is
capable of sinking 10mA and can drive loads connected to
voltages in excess of the positive power supply. This is
useful for driving switches or linear regulators off of a
higher input voltage.
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