LT1120ACS8 [Linear]
Micropower Regulator with Comparator and Shutdown; 微功率稳压器，比较器和关机
| 型号： | LT1120ACS8 |
| 厂家： | 
Linear |
| 描述： | Micropower Regulator with Comparator and Shutdown |
| 文件： | 总8页 (文件大小：219K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1120A
Micropower Regulator with
Comparator and Shutdown
U
FEATURES
DESCRIPTION
■
20µA Supply Current
The LT1120A is a combination micropower positive regu-
lator 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.
■
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
U
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.
APPLICATIONS
■
Battery Systems
■
Battery Backup System
■
Portable Terminals
■
Portable Instruments
■
Memory Keep Alive
U
TYPICAL APPLICATION
5V Regulator
Dropout Voltage and Supply Current
1.00
0.10
0.01
10
5
4
2
V
Q
> 5.2V
IN
V
IN
V
OUT
FB
5V
I
= 20µA
LT1120A
0.001µF
1M
1M
+
+
GND
1
1
10µF
25µF
3
SHUTDOWN
1120A TA01
0.1
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
1120A TA02
1
LT1120A
W W
U W
U
W U
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
Input Voltage ........................................................... 36V
NPN Collector Voltage ............................................. 36V
Output Short-Circuit Duration.......................... Indefinite
Power Dissipation............................... Internally Limited
Operating Temperature Range
ORDER PART
TOP VIEW
NUMBER
GND
FEEDBACK
1
2
3
4
8
7
6
5
–INPUT
COMP OUT
REF
LT1120ACN8
LT1120ACS8
LT1120A
SHUTDOWN
LT1120AC.............................................. 0°C to 100°C
Storage Temperature Range
V
V
IN
OUT
S8 PART
MARKING
N8 PACKAGE
8-LEAD PLASTIC DIP
S8 PACKAGE
8-LEAD PLASTIC SOIC
LT1120AC.......................................... –65°C to 150°C
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.
TJ = 25°C
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reference
Reference Voltage
Line Regulation
Load Regulation
Output Source Current
Output Sink Current
Temperature Stability
Regulator
4.5V ≤ V ≤ 36V
2.46
2.50
0.01
0.3
4
4
1
2.54
0.015
0.6
V
%/V
%
mA
mA
%
IN
4.5V ≤ V ≤ 36V
IN
–2.0mA ≤ I ≤ 2mA, V = 12V
REF
IN
V
IN
V
IN
= 5V
= 5V
2
2
Supply Current
V
IN
V
IN
V
IN
= 6V, I
= 36V, I
= 12V, I
≤ 100µA
20
30
11
25
40
20
µA
µA
mA
OUT
≤ 100µA
OUT
OUT
= 125mA
Output Current
Load Regulation
Line Regulation
Dropout Voltage
(V – V ) ≥ 1V, V ≥ 6V
125
mA
%
%/V
V
V
IN
OUT
IN
(V – V ) ≥ 1V, V ≥ 6V
0.2
0.01
0.02
0.40
0.5
0.015
0.05
0.65
IN
OUT
IN
6V ≤ V ≤ 36V
IN
I
I
= 100µA
= 125mA
OUT
OUT
Feedback Sense Voltage
Shutdown Pin Voltage
V
= 12V
2.44
2.2
2.5
2.56
0.4
V
V
V
µA
nA
µA
mA
IN
Normal
Shutdown
V
V
≤ 0.5V
= 1.4V
1.4
10
15
1
OUT
Shutdown Pin Current
Feedback Bias Current
Minimum Load Current
Short Circuit Current
Comparator
IN
40
5
400
V
V
= 36V
= 36V
IN
250
IN
Offset Voltage
Bias Current
Gain
Power Supply Rejection
Output Sink Current
Saturation Voltage
Input Voltage Range
Response Time
V
V
∆V
= 36V
= 36V
3
15
10000
96
18
0.4
7
40
mV
nA
V/V
dB
mA
V
V
µs
µA
IN
IN
= 29V, R = 20k
2000
80
10
OUT
L
4.5V ≤ V ≤ 36V
S
V
IN
= 4.5V
= 1mA
I
0.6
OUT
0
V
– 1
IN
5
Leakage Current
V
IN
= 36V, V(Pin 7) = 36V
2
2
LT1120A
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reference
Reference Voltage
Line Regulation
Load Regulation
Output Source Current
Output Sink Current
Regulator
4.5V ≤ V ≤ 36V
●
●
●
●
●
2.40
2.50
0.01
0.4
2.55
0.02
0.8
V
%/V
%
mA
mA
IN
4.5V ≤ V ≤ 36V
IN
–2.0mA ≤ I
≤ 2mA, V = 12V
REF
IN
V
V
= 5V
= 5V
2
2
IN
IN
Supply Current
V
V
V
= 6V, I
= 36V, I
= 12V, I
≤ 100µA
●
●
●
30
40
11
40
50
20
µA
µA
mA
IN
IN
IN
OUT
≤ 100µA
OUT
OUT
= 125mA
Output Current
Load Regulation
Line Regulation
Dropout Voltage
(V – V ) ≥ 1V, V ≥ 6V
●
●
●
125
mA
%
%/V
V
V
IN
OUT
IN
(V – V ) ≥ 1V, V ≥ 6V
1
0.02
0.06
0.85
IN
OUT
IN
6V ≤ V ≤ 36V
IN
I
I
= 100µA
= 125mA
●
●
OUT
OUT
Feedback Sense Voltage
Feedback Bias Current
Minimum Load Current
Short Circuit Current
Comparator
V
= 12V
●
●
●
●
2.38
2.5
2.57
50
50
V
nA
µA
mA
IN
V
V
= 36V
= 36V
IN
IN
240
400
Offset Voltage
Bias Current
Gain
Output Sink Current (Note 1)
Leakage Current
V
V
∆V
V
V
= 36V
= 36V
●
●
●
●
●
10
60
mV
nA
V/V
mA
µA
IN
IN
15
10
= 29V, R = 20k
1000
5
OUT
L
= 4.5V
= 36V, V(Pin 7) = 36V
IN
IN
8
The
● denotes specifications which apply over the operating temperature range.
Note 1: For T ≤ –40°C output sink current drops to 2.5mA.
A
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
Regulator Load Regulation
Supply Current
Regulator Short-Circuit Current
0.3
0.2
0.1
100
10
350
300
250
200
150
100
50
PRE-LOAD = 10µ0A
T= –55°C
J
T= 25°C
J
0
–0.1
–0.2
–0.3
1
T= 125°C
J
0.1
0.01
0
0.1
1
10
100
1000
0.1
1
10
100
1000
–50
–10
30
70
110
150
OUTPUT CURRENT (mA)
REGULATOR OUTPUT CURRENT (mA)
TEMPERATURE (°C)
1120A G01
1120A G02
1120A G03
3
LT1120A
TYPICAL PERFORMANCE CHARACTERISTICS
W
U
Dropout Voltage
Regulator Ripple Rejection
Regulator Minimum Load Current
1
70
100
∆V
OUT
= 100mV
65
60
55
50
45
I
= 100mA
OUT
I
= 10mA
OUT
0.1
10
I
= 1mA
OUT
V
= 10VDC,
1Vp-p
IN
40
35
30
V
C
= 5V
OUT
OUT
= 10µF
0.01
10
1
0.1
1
10
100
1000
10
100
1k
10k
100k
70 80 90 100 110 120 130 140 150
REGULATOR OUTPUT CURRENT (mA)
RIPPLE FREQUENCY (Hz)
TEMPERATURE (°C)
1120A G04
1120A G06
1120A G05
Supply Current
Reference Regulation
Supply Current at Dropout
10
4
3
2
I
= 100mA
I
= 100mA
OUT
OUT
1
0.1
1
0.1
1
0
–1
I
= 10mA
I
= 10mA
OUT
OUT
–2
–3
–4
I
= 1mA
5
I
= 1mA
OUT
OUT
V
= 5V
OUT
20
0.01
0.01
1
10
15
25
0
0.1
0.2
0.3
0.4
0.5
0.6
–1.5 –1.0 –0.5
0
0.5
1.0
1.5
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
REFERENCE OUTPUT CURRENT (mA)
1120A G07
1120A G08
1120A G09
Feedback Pin Current
Regulator Thermal Regulation
Turn-On Characteristic
0.1
0
40
35
30
25
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
0
V
V
= 15V
= 5V
V
= 5V
IN
OUT
OUT
NO LOAD
T
= –55°C
J
–0.1
R
= 500Ω
L
20
15
10
5
T
= 25°C
J
50
0
T
J
= 125°C
R
4
= 50Ω
L
0
0
20 40 60 80 100 120 140 160 180
TIME (ms)
0.1
1
10
100
1000
0
1
2
3
5
6
7
8
REGULATOR OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
1120A G11
1120A G10
1120A G12
4
LT1120A
U
U
U
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.
W
BLOCK DIAGRAM
REFERENCE
6
V
5
7
IN
COMPARATOR
OUT
100k
+
–
4
2
3
1
V
OUT
REF
2.5V
FEEDBACK
SHUTDOWN
GROUND
120k
8
–INPUT
1120A BD01
U
W U U
APPLICATIONS INFORMATION
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.
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.
5
LT1120A
U
W U U
APPLICATIONS INFORMATION
Reference
Internal to the LT1120A is a 2.5V trimmed class B output
reference.Thereferencewasdesignedtobeabletosource
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 imped-
ancebyplacinganoutputcapacitoronPin6.Thereference
in the LT1120A becomes unstable with large capacitive
loads placed directly on it. When using an output capaci-
tor, 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
thenacapacitortoground.ThisisshowninFigure1.Other
than placing large capacitive loads on the reference, no
other precautions are necessary and the reference is
stable with nominal stray capacitances.
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 operat-
ingtemperaturestheminimumloadcurrentincreasesand
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.
REF
REF
6
6
OUTPUT
OR
20Ω
20Ω
OUTPUT
+
+
10µF
10µF
1120A AI01
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.
Figure 1. Bypassing Reference
Overload Protection
The main regulator in the LT1120A is current limited at
approximately250mA.Thecurrentlimitisstablewithboth
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
LT1120A
U
TYPICAL APPLICATIONS
Regulator with Output Voltage Monitor
5
V
IN
5V
4
OUTPUT
5V
OUTPUT
+
–
+
LOGIC
500k
0.001µF
98k
2k
10µF
LT1120A
8
2
7
FEEDBACK
LOGIC OUTPUT
100k
REF
6
GND
1
1120A TA03
LOGIC OUTPUT GOES LOW WHEN
DROPS BY 100mV
V
OUT
Compensating the Comparator as an Op Amp
Current Limited 1 Amp Regulator
2.2k
0.5Ω*
6
50µA
V
V
IN
V
+
–
REF
MJE2955
1M
2N3906*
7
5
V
AT A = 100,
V
SLEW RATE = +0.05V/µs
–6V/µs
IN
OUT
5V AT 1A
R2
1M
C2
+
IN
0.22µF
†
220µF
V
R1
C1
OUT
4
2
LT1120A
FB
GND
1
270Ω
100k
A
R1
33Ω
C1
C2
R2
V
–1
* SETS CURRENT
0.1µF
0.001µF 1M
LIMIT BUT INCREASES
DROPOUT VOLTAGE
BY 0.5V.
–10 100Ω 0.047µF
–100 10k
–
–
100k
10k
0.002µF
1120A TA04
†
MUST HAVE LOW
ESR. SEVERAL 100µF
CAPACITORS CAN BE
PARALLELED.
1120A TA06
Battery Backup Regulator
V
OUT
5V
MAIN
4
2
4
5
5
BATTERY
INPUT
V
V
POWER
IN
OUT
+
INPUT
LT1120A
LT1120A
0.001µF
1M
50k
1M
10µF
2
GND
1
GND
1
INTERNAL PARASITIC
DIODES OF LT1120A
1120A TA05
V
V
OUT
IN
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
7
LT1120A
U
PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted.
N8 Package
8-Lead Plastic DIP
0.400
(10.160)
MAX
8
7
6
5
4
0.250 ± 0.010
(6.350 ± 0.254)
1
2
3
0.130 ± 0.005
0.300 – 0.320
0.045 – 0.065
(3.302 ± 0.127)
(1.143 – 1.651)
(7.620 – 8.128)
0.065
(1.651)
TYP
0.009 – 0.015
(0.229 – 0.381)
0.125
0.020
(0.508)
MIN
(3.175)
MIN
+0.025
0.045 ± 0.015
(1.143 ± 0.381)
0.325
–0.015
+0.635
8.255
(
)
–0.381
0.100 ± 0.010
(2.540 ± 0.254)
0.018 ± 0.003
(0.457 ± 0.076)
N8 0392
S8 Package
8-Lead Plastic SOIC (Narrow)
0.189 – 0.197
(4.801 – 5.004)
7
5
8
6
0.228 – 0.244
0.150 – 0.157
(5.791 – 6.197)
(3.810 – 3.988)
1
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
0°– 8° TYP
SO8 0392
LT/GP 0494 10K • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
8
●
●
(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977
LINEAR TECHNOLOGY CORPORATION 1994
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LT1120 - Micropower Regulator with Comparator and Shutdown; Package: SO; Pins: 8; Temperature Range: 0°C to 70°C
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