LT1120A
Micropower Regulator with
Comparator and Shutdown
Features
Description
20µA Supply Current
nn 125mA Output Current
nn 2.5V Reference
nn Reference Output Sources 4mA and Sinks 4mA
nn Open Collector Comparator Sinks 10mA
nn Logic Shutdown
nn 0.2V Dropout Voltage
nn Thermal Limiting
nn 8-Lead SO Package
The LT®1120A is a combination micropower positive regulator and free collector comparator on a single monolithic
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 currents. 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.
Applications
The comparator can be used for system or battery monitoring. 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.
nn
Battery Systems
Battery Backup System
nn Portable Terminals
nn Portable Instruments
nn Memory Keep Alive
nn
nn
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Analog Devices, Inc. All other trademarks are the property of their
respective owners.
Typical Application
5V Regulator
LT1120A
0.001µF
GND
3
SHUTDOWN
5V
1
1M
FB 2
1M
+
25µF
1120A TA01a
1.00
10
0.10
1
0.01
0.1
10
100
1
OUTPUT CURRENT (mA)
SUPPLY CURRENT (mA)
10µF
+
VOUT 4
DROPOUT VOLTAGE (V)
5 V
IN
VIN > 5.2V
IQ = 20µA
Dropout Voltage and Supply Current
0.1
1000
1120A TA01b
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1
LT1120A
Absolute Maximum Ratings
(Note 1)
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
Pin Configuration
TOP VIEW
TOP VIEW
GND 1
8
–INPUT
GND 1
8
–INPUT
FEEDBACK 2
7
COMP OUT
FEEDBACK 2
7
COMP OUT
SHUTDOWN 3
6
REF
SHUTDOWN 3
6
REF
VOUT 4
5
VIN
VOUT 4
5
VIN
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 110°C, θJA = 130°C/W
TJMAX = 110°C, θJA = 190°C/W
Order Information
http://www.linear.com/product/LT1120A#orderinfo
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1120ACN8#PBF
LT1120ACN8#TRPBF
1120ACN8
8-Lead Plastic DIP
0°C to 100°C
LT1120ACS8#PBF
LT1120ACS8#TRPBF
1120A
8-Lead Plastic SO
0°C to 100°C
LT1120AIS8#PBF
LT1120AIS8#TRPBF
1120AI
8-Lead Plastic SO
–40°C to 100°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
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LT1120A
Electrical Characteristics
TJ = 25°C.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reference Voltage
4.5V ≤ VIN ≤ 36V
2.46
2.50
2.54
V
Line Regulation
4.5V ≤ VIN ≤ 36V
0.01
0.015
%/V
Load Regulation
–2.0mA ≤ IREF ≤ 2mA, VIN = 12V
0.3
0.6
Output Source Current
VIN = 5V
2
4
mA
Output Sink Current
VIN = 5V
2
4
mA
1
%
Reference
Temperature Stability
%
Regulator
Supply Current
VIN = 6V, IOUT ≤ 100µA
VIN = 36V, IOUT ≤ 100µA
VIN = 12V, IOUT = 125mA
Output Current
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
Load Regulation
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
0.2
0.5
Line Regulation
6V ≤ VIN ≤ 36V
0.01
0.015
%/V
Dropout Voltage
IOUT = 100µA
IOUT = 125mA
0.02
0.40
0.05
0.65
V
V
Feedback Sense Voltage
VIN = 12V
2.44
2.5
2.56
V
0.4
V
2.2
1.4
VOUT ≤ 0.5V
25
40
20
125
Shutdown
VIN = 1.4V
%
V
10
Feedback Bias Current
µA
µA
mA
mA
Normal
Shutdown Pin Voltage
Shutdown Pin Current
20
30
11
µA
15
40
nA
Minimum Load Current
VIN = 36V
1
5
µA
Short-Circuit Current
VIN = 36V
250
400
mA
Comparator
Offset Voltage
VIN = 36V
3
7
mV
Bias Current
VIN = 36V
15
40
nA
Gain
∆VOUT = 29V, RL = 20k
2000
10000
V/V
Power Supply Rejection
4.5V ≤ VS ≤ 36V
80
96
dB
Output Sink Current
VIN = 4.5V
10
18
mA
Saturation Voltage
IOUT = 1mA
0.4
Input Voltage Range
Leakage Current
VIN – 1
0
Response Time
0.6
5
VIN = 36V, V(Pin 7) = 36V
V
V
µs
2
µA
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3
LT1120A
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TJ = 25°C.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
2.40
2.50
2.55
V
Reference
Reference Voltage
4.5V ≤ VIN ≤ 36V
l
Line Regulation
4.5V ≤ VIN ≤ 36V
l
0.01
0.02
%/V
Load Regulation
–2.0mA ≤ IREF ≤ 2mA, VIN = 12V
l
0.4
0.8
%
Output Source Current
VIN = 5V
l
2
mA
Output Sink Current
VIN = 5V
l
2
mA
Supply Current
VIN = 6V, IOUT ≤ 100µA
VIN = 36V, IOUT ≤ 100µA
VIN = 12V, IOUT = 125mA
l
l
l
Output Current
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
l
Regulator
30
40
11
40
50
20
125
µA
µA
mA
mA
Load Regulation
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
l
1
Line Regulation
6V ≤ VIN ≤ 36V
l
0.02
%/V
Dropout Voltage
IOUT = 100µA
IOUT = 125mA
l
l
0.06
0.85
V
V
Feedback Sense Voltage
VIN = 12V
l
2.57
V
2.38
2.5
%
l
50
nA
Minimum Load Current
VIN = 36V
l
50
µA
Short-Circuit Current
VIN = 36V
l
400
mA
Offset Voltage
VIN = 36V
l
10
mV
Bias Current
VIN = 36V
l
60
nA
Gain
∆VOUT = 29V, RL = 20k
l
1000
Output Sink Current (Note 2)
VIN = 4.5V
l
5
Leakage Current
VIN = 36V, V(Pin 7) = 36V
l
Feedback Bias Current
240
Comparator
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
15
V/V
10
mA
8
µA
Note 2: For TA ≤ –40°C output sink current drops to 2.5mA.
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LT1120A
Typical Performance Characteristics
Regulator Load Regulation
0.2
TJ = –55°C
TJ = 25°C
0.1
0
TJ = 125°C
–0.1
10
1
0.1
–0.2
–0.3
0.1
1
10
100
OUTPUT CURRENT (mA)
0.01
0.1
1000
50
–10
Regulator Ripple Rejection
RIPPLE REJECTION (dB)
10
IOUT = 100mA
60
55
IOUT = 10mA
50
IOUT = 1mA
45
VIN = 10VDC,
1VP-P
VOUT = 5V
COUT = 10µF
40
35
1
1
1000
10
100
REGULATOR OUTPUT CURRENT (mA)
70
80
90
30
100 110 120 130 140 150
TEMPERATURE (°C)
10
Supply Current
Supply Current at Dropout
Reference Regulation
IOUT = 100mA
SUPPLY CURRENT (mA)
1
IOUT = 1mA
VOUT = 5V
5
1
10
25
15
20
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
1120A G07
IOUT = 10mA
0.1
0.01
0.1
0
0.2
0.6
0.3
0.5
0.4
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
1120A G08
REFERENCE VOLTAGE CHANGE (mV)
4
IOUT = 100mA
IOUT = 10mA
100k
1120A G06
10
1
100
1k
10k
RIPPLE FREQUENCY (Hz)
1120A G05
10
150
30
70
110
TEMPERATURE (°C)
70
1120A G04
SUPPLY CURRENT (mA)
100
65
0.1
0.01
150
Regulator Minimum Load Current
∆VOUT = 100mV
IOUT = 1mA
200
1120A G03
100
MINIMUM LOAD CURRENT (µA)
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
Dropout Voltage
0.1
250
1120A G02
1
0.1
300
0
–50
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
1120A G01
0.01
Regulator Short-Circuit Current
350
SHORT-CIRCUIT CURRENT (mA)
PRE-LOAD = 100µA
Supply Current
100
SUPPLY CURRENT (mA)
OUTPUT VOLTAGE CHANGE (%)
0.3
3
2
1
0
–1
–2
–3
–4
–1.5
–1.0 –0.5
0
0.5
1.0
REFERENCE OUTPUT CURRENT (mA)
1.5
1120A G09
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5
LT1120A
Typical Performance Characteristics
30
TJ = –55°C
25
20
15
TJ = 25°C
10
TJ = 125°C
5
0
0.1
1
1000
10
100
REGULATOR OUTPUT CURRENT (mA)
0.1
Regulator Thermal Regulation
Turn-On Characteristics
5.5
VIN = 15V
VOUT = 5V
VOUT = 5V
5.0
0
OUTPUT VOLTAGE (V)
FEEDBACK PIN CURRENT (nA)
35
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE CHANGE (%)
Feedback Pin Current
40
–0.1
50
NO LOAD
4.5
4.0
RL = 500Ω
3.5
3.0
2.5
2.0
0
0
20 40 60 80 100 120 140 160 180
TIME (ms)
0
RL = 50Ω
0
1
2
3
4
5
6
INPUT VOLTAGE (V)
1120A G11
1120A G10
7
8
1120A G12
Pin Functions
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.
VOUT (Pin 4): Main output, requires 10µF output capacitor.
Can be shorted to VIN or ground without damaging device.
VIN (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 VIN). Short-circuit
protected.
–INPUT (Pin 8): Inverting Comparator Input.
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LT1120A
Block Diagram
REF
6
VIN
5
100k
+
COMP OUT
7
–
REF
2.5V
120k
8
–INPUT
4
VOUT
2
FEEDBACK
3
SHUTDOWN
1
GROUND
1120A BD01
Applications Information
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 application 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.
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.
Reference
Internal to the LT1120A is a 2.5V trimmed class B output reference. The reference was designed to be able
to source or sink current so it could be used in supply
splitting applications as well as a general purpose reference for external circuitry. The design of the reference
allows it to source and sink typically 4mA. The available source and sink current decreases as temperature
increases. It is sometimes desirable to decrease the AC
output impedance by placing an output capacitor on Pin
6. The reference in the LT1120A becomes unstable with
large capacitive loads placed directly on it. When using an
output capacitor, about 20Ω should be used to isolate the
capacitor from the reference pin. This 20Ω resistor can be
placed directly in series with the capacitor or alternatively
the reference line can have 20Ω placed in series with it
and then a capacitor to ground. This is shown in Figure 1.
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7
LT1120A
Applications Information
Other than placing large capacitive loads on the reference,
no other precautions are necessary and the reference is
stable with nominal stray capacitances.
REF
REF
6
6
OUTPUT
20Ω
+
10µF
OR
20Ω
+
OUTPUT
10µF
1120A F01
Figure 1. Bypassing Reference
Overload Protection
The main regulator in the LT1120A is current limited at
approximately 250mA. The current limit is stable with
both input voltage and temperature.
Like most other IC regulators, a minimum load is required
on the output of the LT1120A to maintain regulation. For
most standard regulators this is normally specified at
5mA. Of course, for a micropower regulator this would be
a tremendously large current. The output current must be
large enough to absorb all the leakage current of the pass
transistor at the maximum operating temperature. It also
affects the transient response; low output currents have
long recovery times from load transients. At high operating temperatures the minimum load current increases and
having too low of a load current may cause the output
to go unregulated. Devices are tested for minimum load
current at high temperature. The output voltage setting
resistors to the feedback terminal can usually be used to
provide the minimum load current.
Frequency Compensation
The LT1120A is frequency compensated by a dominant
pole on the output. An output capacitor of 10µF is usually large enough to provide good stability. Increasing
the output capacitor above 10µF further improves stability. In order to ensure stability, a feedback capacitor
is needed between the output pin and the feedback pin.
This is because stray capacitance can form another pole
with the large value of feedback resistors used with the
LT1120A. Also, a feedback capacitor minimizes noise
pickup and improves ripple rejection.
With the large dynamic operating range of the output
current, 10000:1, frequency response changes widely.
Low AC impedance capacitors are needed to insure
stability. While solid tantalum are best, aluminum electrolytics can be used but larger capacitor values may be
needed.
1120afb
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LT1120A
Typical Applications
Regulator with Output Voltage Monitor
5
VIN
5V
LOGIC
LOGIC
OUTPUT
–
500k
7
4
OUTPUT
0.001µF
8
LT1120A
+
REF
6
OUTPUT
5V
10µF
VOUT
PIN 7
2k
2
FEEDBACK
98k
+
LOGIC OUTPUT
100k
GND
1
1120A TA03
LOGIC OUTPUT GOES LOW WHEN
VOUT DROPS BY 100mV
Compensating the Comparator as an Op Amp
VREF
6
50µA
+
7
–
IN
R2
AT AV = 100,
SLEW RATE = +0.05V/µs
–6V/µs
1M
C2
R1
C1
AV
–1
–10
–100
R1
33Ω
100Ω
10k
C1
0.1µF
0.047µF
0.002µF
C2
0.001µF
–
–
R2
1M
100k
10k
1120A TA04
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9
LT1120A
Typical Applications
Battery Backup Regulator
5
BATTERY
INPUT
VOUT
VIN
LT1120A
FB
GND
1
VOUT
5V
4
0.001µF
2
1M
+
4
10µF
2
VOUT
VIN
LT1120A
FB
MAIN
POWER
INPUT
GND
1
50k
1M
INTERNAL PARASITIC
DIODES OF LT1120A
VIN
5
1120A TA05
VOUT
Current Limited 1 Amp Regulator
0.5Ω*
2.2k
MJE2955
5
VIN
0.22µF
1M
VIN
2N3906*
+
VOUT
5V AT 1A
220µF†
VOUT 4
LT1120A
GND
1
FB 2
270Ω
100k
* SETS CURRENT
LIMIT BUT INCREASES
DROPOUT VOLTAGE
BY 0.5V.
† MUST HAVE LOW
ESR. SEVERAL 100µF
CAPACITORS CAN BE
PARALLELED.
1120A TA06
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LT1120A
Package Description
Please refer to http://www.linear.com/product/LT1120A#packaging for the most recent package drawings.
N Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510 Rev I)
.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
.255 ±.015*
(6.477 ±0.381)
.300 – .325
(7.620 – 8.255)
.008 – .015
(0.203 – 0.381)
(
+.035
.325 –.015
8.255
+0.889
–0.381
)
.045 – .065
(1.143 – 1.651)
.065
(1.651)
TYP
.100
(2.54)
BSC
.130 ±.005
(3.302 ±0.127)
.120
(3.048) .020
MIN
(0.508)
MIN
.018 ±.003
N8 REV I 0711
(0.457 ±0.076)
NOTE:
1. DIMENSIONS ARE
INCHES
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
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11
LT1120A
Package Description
Please refer to http://www.linear.com/product/LT1120A#packaging for the most recent package drawings.
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610 Rev G)
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
.050 BSC
8
.245
MIN
.160 ±.005
.010 – .020
× 45°
(0.254 – 0.508)
2
.053 – .069
(1.346 – 1.752)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
5
.150 – .157
(3.810 – 3.988)
NOTE 3
1
RECOMMENDED SOLDER PAD LAYOUT
.008 – .010
(0.203 – 0.254)
6
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
NOTE:
1. DIMENSIONS IN
7
.014 – .019
(0.355 – 0.483)
TYP
INCHES
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
3
4
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
SO8 REV G 0212
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LT1120A
Revision History
(Revision history begins at Rev B)
REV
DATE
DESCRIPTION
B
05/17
Changed units in Electrical Characteristics Regulator section
PAGE NUMBER
3
1120afb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection
of its information
circuits as described
herein will not infringe on existing patent rights.
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13
LT1120A
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
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LT1963/LT1963A
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200mA, Low Noise Micropower
Negative, LDO
VIN: –1.9V to –20V; VOUT(MIN) = –1.21V; Dropout Voltage = 0.34V; IQ = 30µA; ISD < 3µA; VOUT = Adj,
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–5V; MS8E Package. Low Noise < 100µVRMS, Stable with Ceramic Capacitors
VIN: 2.7V to 20V; VOUT(MIN) = 1.21V; Dropout Voltage = 0.34V; IQ = 1mA; ISD < 1µA; VOUT = 1.8V,
2.5V, 3.3; DD, TO220, Packages. Low Noise < 40µVRMS, “A” Version Stable with Ceramic Capacitors
1120afb
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LT 0517 REV B • PRINTED IN USA
www.linear.com/LT1120A
LINEAR TECHNOLOGY CORPORATION 1994
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