LINER LT1120AC Micropower regulator with comparator and shutdown Datasheet

LT1120A
Micropower Regulator with
Comparator and Shutdown
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DESCRIPTION
FEATURES
■
■
■
■
■
■
■
■
■
■
20µA Supply Current
8-Lead SOIC
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
The LT1120A 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.
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APPLICATIONS
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Battery Systems
Battery Backup System
Portable Terminals
Portable Instruments
Memory Keep Alive
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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.
TYPICAL APPLICATION
VOUT 4
LT1120A
+
GND
10µF
3
5V
0.001µF
1
1M
+
FB 2
25µF
1M
SHUTDOWN
1.00
10
0.10
1
SUPPLY CURRENT (mA)
5 V
IN
VIN > 5.2V
IQ = 20µA
Dropout Voltage and Supply Current
DROPOUT VOLTAGE (V)
5V Regulator
1120A TA01
0.01
0.1
1
10
100
OUTPUT CURRENT (mA)
0.1
1000
1120A TA02
1
LT1120A
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W W
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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
Storage Temperature Range
LT1120AC .......................................... –65°C to 150°C
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
GND
1
8
–INPUT
FEEDBACK
2
7
COMP OUT
SHUTDOWN
3
6
REF
VOUT
4
5
VIN
LT1120A
N8 PACKAGE
8-LEAD PLASTIC DIP
LT1120ACN8
LT1120ACS8
S8 PART
MARKING
S8 PACKAGE
8-LEAD PLASTIC SOIC
1120A POI01
TJMAX = 110°C, θJA = 130°C/ W (N)
TJMAX = 110°C, θJA = 190°C/ W (S)
1120A
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER
Reference
Reference Voltage
Line Regulation
Load Regulation
Output Source Current
Output Sink Current
Temperature Stability
Regulator
Supply Current
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
2
TJ = 25°C
CONDITIONS
MIN
4.5V ≤ VIN ≤ 36V
4.5V ≤ VIN ≤ 36V
–2.0mA ≤ IREF ≤ 2mA, VIN = 12V
VIN = 5V
VIN = 5V
2.46
VIN = 6V, IOUT ≤ 100µA
VIN = 36V, IOUT ≤ 100µA
VIN = 12V, IOUT = 125mA
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
6V ≤ VIN ≤ 36V
IOUT = 100µA
IOUT = 125mA
VIN = 12V
Normal
VOUT ≤ 0.5V
Shutdown
VIN = 1.4V
2
2
MAX
UNITS
2.50
2.54
0.015
0.6
V
%/V
%
mA
mA
%
20
30
11
25
40
20
0.2
0.01
0.02
0.40
2.5
0.5
0.015
0.05
0.65
2.56
0.4
µA
µA
mA
mA
%
%/V
V
V
V
V
V
µA
nA
µA
mA
0.01
0.3
4
4
1
125
2.44
2.2
VIN = 36V
VIN = 36V
VIN = 36V
VIN = 36V
∆VOUT = 29V, RL = 20k
4.5V ≤ VS ≤ 36V
VIN = 4.5V
IOUT = 1mA
TYP
2000
80
10
1.4
10
15
1
250
3
15
10000
96
18
0.4
0
40
5
400
7
40
0.6
VIN – 1
5
VIN = 36V, V(Pin 7) = 36V
2
mV
nA
V/V
dB
mA
V
V
µs
µA
LT1120A
ELECTRICAL CHARACTERISTICS
PARAMETER
Reference
Reference Voltage
Line Regulation
Load Regulation
Output Source Current
Output Sink Current
Regulator
Supply Current
CONDITIONS
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 1)
Leakage Current
4.5V ≤ VIN ≤ 36V
4.5V ≤ VIN ≤ 36V
–2.0mA ≤ IREF ≤ 2mA, VIN = 12V
VIN = 5V
VIN = 5V
●
VIN = 6V, IOUT ≤ 100µA
VIN = 36V, IOUT ≤ 100µA
VIN = 12V, IOUT = 125mA
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
6V ≤ VIN ≤ 36V
IOUT = 100µA
IOUT = 125mA
VIN = 12V
●
●
●
MIN
TYP
MAX
UNITS
2.40
2.50
0.01
0.4
2.55
0.02
0.8
V
%/V
%
mA
mA
30
40
11
40
50
20
µA
µA
mA
mA
%
%/V
V
V
V
nA
µA
mA
●
●
●
●
●
2
2
125
240
1
0.02
0.06
0.85
2.57
50
50
400
15
10
60
●
●
●
●
●
2.38
2.5
●
VIN = 36V
VIN = 36V
●
VIN = 36V
VIN = 36V
∆VOUT = 29V, RL = 20k
VIN = 4.5V
VIN = 36V, V(Pin 7) = 36V
●
●
●
●
●
1000
5
mV
nA
V/V
mA
µA
10
8
●
The ● denotes specifications which apply over the operating temperature range.
Note 1: For TA ≤ –40°C output sink current drops to 2.5mA.
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TYPICAL PERFORMANCE CHARACTERISTICS
Regulator Load Regulation
PRE-LOAD = 100 µA
Supply Current
Regulator Short-Circuit Current
350
100
T J = –55°C
T J = 25°C
0.1
0
T J = 125°C
–0.1
SHORT-CIRCUIT CURRENT (mA)
0.2
SUPPLY CURRENT (mA)
OUTPUT VOLTAGE CHANGE (%)
0.3
10
1
0.1
–0.2
–0.3
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
1120A G01
0.01
0.1
1
1000
10
100
REGULATOR OUTPUT CURRENT (mA)
1120A G02
300
250
200
150
100
50
0
–50
–10
110
30
70
TEMPERATURE (°C)
150
1120A G03
3
LT1120A
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TYPICAL PERFORMANCE CHARACTERISTICS
70
∆VOUT = 100mV
0.1
RIPPLE REJECTION (dB)
65
10
0.01
0.1
1
70
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
55
I OUT = 10mA
50
I OUT = 1mA
45
VIN = 10VDC,
1Vp-p
VOUT = 5V
COUT = 10µF
40
30
80
90
Supply Current
SUPPLY CURRENT (mA)
I OUT = 10mA
1
I OUT = 10mA
0.1
I OUT = 1mA
VOUT = 5V
0.01
REFERENCE VOLTAGE CHANGE (mV)
4
I OUT = 100mA
I OUT = 1mA
0.01
5
1
10
25
15
20
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
TJ = –55°C
25
20
15
TJ = 25°C
10
5
0
0.1
TJ = 125°C
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
1120A G10
1
0
–1
–2
–3
–1.0 –0.5
0.5
1.0
0
REFERENCE OUTPUT CURRENT (mA)
1.5
1120A G09
Regulator Thermal Regulation
Turn-On Characteristic
0.1
5.5
VIN = 15V
VOUT = 5V
VOUT = 5V
5.0
NO LOAD
0
OUTPUT VOLTAGE (V)
30
OUTPUT CURRENT (mA)
35
2
1120A G08
OUTPUT VOLTAGE CHANGE (%)
Feedback Pin Current
40
3
–4
–1.5
0.1
0
0.2
0.6
0.3
0.5
0.4
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
1120A G07
4
Reference Regulation
Supply Current at Dropout
I OUT = 100mA
0.1
100k
1120A G06
10
1
100
10k
1k
RIPPLE FREQUENCY (Hz)
10
100 110 120 130 140 150
TEMPERATURE (°C)
1120A G05
10
SUPPLY CURRENT (mA)
I OUT = 100mA
60
35
1120A G04
FEEDBACK PIN CURRENT (nA)
Regulator Ripple Rejection
Regulator Minimum Load Current
100
MINIMUM LOAD CURRENT (µA)
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
Dropout Voltage
1
–0.1
50
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)
1120A G11
RL = 50Ω
0
0
1
2
3
4
5
6
INPUT VOLTAGE (V)
7
8
1120A G12
LT1120A
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PIN FUNCTIONS
Pin 1 (Ground).
Pin 5 (Input Supply): Bypass with 10µF cap. Must always
be more positive than ground.
Pin 2 (Feedback): 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.
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.
Pin 7 (Comparator Output): May be connected to any
voltage from ground to 36V more positive than ground
(operates above VIN). Short circuit protected.
Pin 3 (Shutdown): A logic 1 shuts off main regulator.
Caution: noise or leakage into the shutdown pin can affect
output voltage.
Pin 8 (Comparator Input): Inverting comparator input.
Pin 4 (Regulator Output): Main output, requires 10µF
output capacitor. Can be shorted to VIN or ground without
damaging device.
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BLOCK DIAGRAM
REFERENCE
6
VIN
5
COMPARATOR
OUT
7
100k
+
–
REF
2.5V
4
VOUT
2
FEEDBACK
3
SHUTDOWN
1
GROUND
120k
8
–INPUT
1120A BD01
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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.
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LT1120A
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APPLICATIONS INFORMATION
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. 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 AI01
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
6
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.
LT1120A
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TYPICAL APPLICATIONS
Regulator with Output Voltage Monitor
5
VIN
5V
OUTPUT
LOGIC
+
–
500k
0.001µF
+
FEEDBACK
LOGIC OUTPUT
98k
10µF
8
LT1120A
7
OUTPUT
5V
4
REF
6
2k
2
100k
GND
1
1120A TA03
LOGIC OUTPUT GOES LOW WHEN
VOUT DROPS BY 100mV
Compensating the Comparator as an Op Amp
VREF
6
0.5Ω*
2.2k
50µA
+
R2
VIN
MJE2955
7
–
IN
Current Limited 1 Amp Regulator
1M
+
0.22µF
C2
R1
33Ω
100Ω
10k
C1
0.1µF
0.047µF
0.002µF
1M
VOUT
5V AT 1A
220µF†
VOUT 4
R1
C1
AV
–1
–10
–100
2N3906*
5
VIN
AT AV = 100,
SLEW RATE = +0.05V/µs
– 6V/µs
LT1120A
FB 2
GND
1
C2
R2
0.001µF 1M
–
100k
–
10k
270Ω
100k
1120A TA04
* SETS CURRENT
LIMIT BUT INCREASES
DROPOUT VOLTAGE
BY 0.5V.
† MUST HAVE LOW
ESR. SEVERAL 100µF
CAPACITORS CAN BE
PARALLELED.
1120A TA06
Battery Backup Regulator
VOUT
5V
5
BATTERY
INPUT
VOUT
VIN
+
LT1120A
GND
1
0.001µF
FB
1M
2
VIN
VOUT
5
LT1120A
10µF
2
50k
INTERNAL PARASITIC
DIODES OF LT1120A
VIN
4
4
FB
MAIN
POWER
INPUT
GND
1
1M
1120A TA05
VOUT
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 circuits as described herein will not infringe on existing patent rights.
7
LT1120A
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PACKAGE DESCRIPTION
Dimension in inches (millimeters) unless otherwise noted.
N8 Package
8-Lead Plastic DIP
0.400
(10.160)
MAX
8
7
6
5
0.250 ± 0.010
(6.350 ± 0.254)
1
0.300 – 0.320
(7.620 – 8.128)
+0.635
–0.381
4
0.130 ± 0.005
(3.302 ± 0.127)
0.065
(1.651)
TYP
+0.025
0.325 –0.015
8.255
3
0.045 – 0.065
(1.143 – 1.651)
0.009 – 0.015
(0.229 – 0.381)
(
2
0.125
(3.175)
MIN
0.045 ± 0.015
(1.143 ± 0.381)
)
0.020
(0.508)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
0.100 ± 0.010
(2.540 ± 0.254)
N8 0392
S8 Package
8-Lead Plastic SOIC (Narrow)
0.189 – 0.197
(4.801 – 5.004)
8
7
6
5
0.228 – 0.244
(5.791 – 6.197)
0.150 – 0.157
(3.810 – 3.988)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
8
0.016 – 0.050
0.406 – 1.270
Linear Technology Corporation
3
4
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
2
0.014 – 0.019
(0.355 – 0.483)
0.050
(1.270)
BSC
SO8 0392
LT/GP 0494 10K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
 LINEAR TECHNOLOGY CORPORATION 1994
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