LINER LT1120A_04

LT1120A
Micropower Regulator with
Comparator and Shutdown
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FEATURES
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DESCRIPTIO
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.
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
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APPLICATIO S
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Battery Systems
Battery Backup System
Portable Terminals
Portable Instruments
Memory Keep Alive
, LTC and LT are registered trademarks of Linear Technology Corporation.
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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 APPLICATIO
VOUT 4
+
GND
10µF
3
SHUTDOWN
5V
0.001µF
LT1120A
1
1M
+
FB 2
25µF
1M
1120A TA01
1.00
10
0.10
1
0.01
0.1
1
10
100
OUTPUT CURRENT (mA)
SUPPLY CURRENT (mA)
5 V
IN
VIN > 5.2V
IQ = 20µA
Dropout Voltage and Supply Current
DROPOUT VOLTAGE (V)
5V Regulator
0.1
1000
1120A TA02
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LT1120A
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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
LT1120AI ......................................... – 40°C to 100°C
Storage Temperature Range ................. – 65°C to 150°C
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(Note 1)
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
TOP VIEW
GND 1
8
–INPUT
FEEDBACK 2
7
COMP OUT
SHUTDOWN 3
6
REF
VOUT 4
5
VIN
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 110°C, θJA = 130°C/W (N)
TJMAX = 110°C, θJA = 190°C/W (S)
ORDER PART
NUMBER
LT1120ACN8
LT1120ACS8
LT1120AIS8
S8 PART
MARKING
1120A
1120AI
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
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
TJ = 25°C
CONDITIONS
MIN
TYP
MAX
UNITS
4.5V ≤ VIN ≤ 36V
4.5V ≤ VIN ≤ 36V
–2.0mA ≤ IREF ≤ 2mA, VIN = 12V
VIN = 5V
VIN = 5V
2.46
2.50
0.01
0.3
4
4
1
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
VIN = 6V, IOUT ≤ 100mA
VIN = 36V, IOUT ≤ 100mA
VIN = 12V, IOUT = 125mA
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
(VIN – VOUT) ≥ 1V, VIN ≥ 6V
6V ≤ VIN ≤ 36V
IOUT = 100mA
IOUT = 125mA
VIN = 12V
Normal
VOUT ≤ 0.5V
Shutdown
VIN = 1.4V
2
2
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
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
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LT1120A
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range of TJ = 25°C.
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 2)
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
●
●
Note 1: Absolute Maximum Ratings are those values beyond which the life
to the device may be impaired.
●
●
●
1000
5
mV
nA
V/V
mA
µA
10
8
●
Note 2: For TA ≤ –40°C output sink current drops to 2.5mA.
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TYPICAL PERFOR A CE CHARACTERISTICS
Regulator Load Regulation
Supply Current
PRE-LOAD = 100µA
350
TJ = –55°C
TJ = 25°C
0.1
0
TJ = 125°C
–0.1
SHORT-CIRCUIT CURRENT (mA)
0.2
SUPPLY CURRENT (mA)
OUTPUT VOLTAGE CHANGE (%)
Regulator Short-Circuit Current
100
0.3
10
1
0.1
–0.2
–0.3
0.1
1
100
10
OUTPUT CURRENT (mA)
1000
1120A G01
0.01
0.1
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
1120A G02
300
250
200
150
100
50
0
–50
–10
30
70
110
TEMPERATURE (°C)
150
1120A G03
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LT1120A
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TYPICAL PERFOR A CE CHARACTERISTICS
Regulator Minimum Load Current
∆VOUT = 100mV
RIPPLE REJECTION (dB)
65
0.1
10
0.01
55
IOUT = 10mA
50
IOUT = 1mA
45
VIN = 10VDC,
1VP-P
VOUT = 5V
COUT = 10µF
40
30
1
10
100
1
1000
REGULATOR OUTPUT CURRENT (mA)
70
80
90
Supply Current
Reference Regulation
Supply Current at Dropout
10
IOUT = 100mA
SUPPLY CURRENT (mA)
IOUT = 10mA
IOUT = 1mA
1
IOUT = 1mA
VOUT = 5V
0.01
1
5
20
15
10
25
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
IOUT = 10mA
0.1
0.01
TJ = –55°C
25
20
15
TJ = 25°C
10
TJ = 125°C
5
0
0.1
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
3
–4
–1.5
0
0.1
0.5
0.3
0.4
0.2
0.6
REGULATOR INPUT-OUTPUT DIFFERENTIAL (V)
1120A G07
40
REFERENCE VOLTAGE CHANGE (mV)
4
IOUT = 100mA
0.1
100k
1120A G06
1120A G05
10
1
100
1k
10k
RIPPLE FREQUENCY (Hz)
10
100 110 120 130 140 150
TEMPERATURE (°C)
1120A G04
SUPPLY CURRENT (mA)
IOUT = 100mA
60
35
0.1
FEEDBACK PIN CURRENT (nA)
Regulator Ripple Rejection
70
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
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LT1120A
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PI FU CTIO S
GND (Pin 1): Ground
VIN (Pin 5): Input Supply. Bypass with 10µF capacitor.
Must always be more positive than 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.
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.
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.
–INPUT (Pin 8): Inverting Comparator Input.
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BLOCK DIAGRA
REF
6
VIN
5
100k
+
COMP OUT
7
–
REF
2.5V
4
VOUT
2
FEEDBACK
3
SHUTDOWN
1
GROUND
120k
8
–INPUT
1120A BD01
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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 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
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.
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LT1120A
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TYPICAL APPLICATIO S
Regulator with Output Voltage Monitor
5
VIN
5V
OUTPUT
LOGIC
+
–
500k
0.001µF
7
LOGIC
OUTPUT
OUTPUT
5V
4
98k
10µF
VOUT
8
LT1120A
PIN 7
+
FEEDBACK
REF
6
2k
2
LOGIC OUTPUT
100k
GND
1
1120A TA03
LOGIC OUTPUT GOES LOW WHEN
VOUT DROPS BY 100mV
Compensating the Comparator as an Op Amp
Current Limited 1 Amp Regulator
0.5Ω*
2.2k
VREF
6
+
MJE2955
IN
AT AV = 100,
SLEW RATE = +0.05V/µs
– 6V/µs
1M
VOUT
5V AT 1A
220µF†
VOUT 4
LT1120A
R1
C1
R1
33Ω
100Ω
10k
+
0.22µF
1M
C2
AV
–1
–10
–100
2N3906*
5
VIN
7
–
R2
VIN
50µA
C1
0.1µF
0.047µF
0.002µF
FB 2
GND
1
C2
R2
0.001µF 1M
–
100k
–
10k
270Ω
100k
* SETS CURRENT
LIMIT BUT INCREASES
DROPOUT VOLTAGE
BY 0.5V.
† MUST HAVE LOW
1120A TA04
ESR. SEVERAL 100µF
CAPACITORS CAN BE
PARALLELED.
1120A TA06
Battery Backup Regulator
VOUT
5V
5
BATTERY
INPUT
VIN
VOUT
+
LT1120A
GND
1
0.001µF
FB
1M
2
VOUT
VIN
LT1120A
10µF
2
50k
INTERNAL PARASITIC
DIODES OF LT1120A
VIN
4
4
FB
5
MAIN
POWER
INPUT
GND
1
1M
1120A TA05
VOUT
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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.
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LT1120A
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PACKAGE DESCRIPTIO
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.300 – .325
(7.620 – 8.255)
.045 – .065
(1.143 – 1.651)
.065
(1.651)
TYP
.008 – .015
(0.203 – 0.381)
(
+.035
.325 –.015
+0.889
8.255
–0.381
.400*
(10.160)
MAX
.130 ± .005
(3.302 ± 0.127)
)
8
7
6
1
2
3
5
.255 ± .015*
(6.477 ± 0.381)
.120
(3.048) .020
MIN
(0.508)
MIN
.018 ± .003
(0.457 ± 0.076)
.100
(2.54)
BSC
4
N8 1002
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)
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
NOTE 3
.010 – .020
× 45°
(0.254 – 0.508)
.008 – .010
(0.203 – 0.254)
.004 – .010
(0.101 – 0.254)
.053 – .069
(1.346 – 1.752)
8
7
6
.045 ±.005
.050 BSC
5
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. DIMENSIONS IN
.050
(1.270)
BSC
.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)
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
SO8 0303
1
2
3
4
.245
MIN
.160 ±.005
.030 ±.005
TYP
RECOMMENDED SOLDER PAD LAYOUT
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ThinSOT is a trademark of Linear Technology Corporation.
COMMENTS
VIN: 1.8V to 20V; VOUT(MIN) = 1.22V; Dropout Voltage = 0.30V; IQ = 20µA; ISD < 1µA; VOUT = Adj,
1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V; ThinSOTTM/MS8 Packages. Low Noise <20µVRMSP-P
VIN: 1.8V to 20V; VOUT(MIN) = 1.22V; Dropout Voltage = 0.30V; IQ = 30µA; ISD < 1µA;
VOUT = 1.5V, 1.8V, 2.5V,3V, 3.3V, 5V; SO-8 Package. Low Noise <20µVRMSP-P
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 <40µVRMSP-P, “A” Version Stable
with Ceramic Capacitors
VIN: 1.8V to 20V; VOUT(MIN) = 1.22V; Dropout Voltage = 0.27V; IQ = 30µA; ISD < 1µA;
VOUT = 1.5V, 1.8V, 2.5V,3V, 3.3V, 5V; MS8 Package. Low Noise <20µVRMSP-P
VIN: 2.1V to 20V; VOUT(MIN) = 1.21V; Dropout Voltage = 34V; IQ = 1mA; ISD < 1µA; VOUT = 1.5V
1.8V, 2.5V, 3.3; DD, TO220, SOT-223, SO-8 Packages. Low Noise <40µVRMSP-P, “A”
Version Stable with Ceramic Capacitors
VIN: –0.9V to –20V; VOUT(MIN) = –1.21V; Dropout Voltage = 0.34V; IQ = 30µA; ISD < 3µA;
VOUT = Adj, –5V; ThinSOT Package. Low Noise <30µVRMSP-P, Stable with Ceramic Capacitors
VIN: 1.5V to 80V; VOUT(MIN) = 1.28V; Dropout Voltage = 0.30V; IQ = 30µA; ISD < 1µA;
VOUT = Adj, –5V; MS8E Package. Low Noise <100µVRMSP-P, Stable with Ceramic Capacitors
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Linear Technology Corporation
LT/TP 0104 1K REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 1994