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LT1120A Micropower Regulator with Comparator and Shutdown
FEATURES
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DESCRIPTIO
20A 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(R)1120A is a combination micropower positive regulator and free collector comparator on a single monolithic chip. With only 20A 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. 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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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
0.001F FB 2
1M
+
10F 3 SHUTDOWN
GND 1
+
25F 1M
1120A TA01
DROPOUT VOLTAGE (V)
VIN > 5.2V IQ = 20A
5V IN
VOUT 4
5V
0.10
0.01 0.1 1 10 100 OUTPUT CURRENT (mA)
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SUPPLY CURRENT (mA)
1 0.1 1000
1120A TA02
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LT1 120A
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW GND 1 FEEDBACK 2 SHUTDOWN 3 VOUT 4 N8 PACKAGE 8-LEAD PDIP 8 7 6 5 -INPUT COMP OUT REF VIN
Input Voltage ........................................................... 36V NPN Collector Voltage ............................................. 36V Output Short-Circuit Duration .......................... Indefinite Power Dissipation ............................... Internally Limited Operating Temperature Range LT1120AC ............................................. 0C to 100C LT1120AI ......................................... - 40C to 100C Storage Temperature Range ................. - 65C to 150C
ORDER PART NUMBER LT1120ACN8 LT1120ACS8 LT1120AIS8 S8 PART MARKING 1120A 1120AI
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 110C, JA = 130C/W (N) TJMAX = 110C, JA = 190C/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
TJ = 25C
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 % A A mA mA % %/V V V V V V A nA A mA mV nA V/V dB mA V V s A
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4.5V VIN 36V 4.5V VIN 36V -2.0mA IREF 2mA, VIN = 12V VIN = 5V VIN = 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
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 VIN = 36V VIN = 36V VIN = 36V VIN = 36V VOUT = 29V, RL = 20k 4.5V VS 36V VIN = 4.5V IOUT = 1mA
25 40 20
2.44 2.2
40 5 400 7 40
2000 80 10 0
0.6 VIN - 1 2
VIN = 36V, V(Pin 7) = 36V
2
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LT1120A
ELECTRICAL CHARACTERISTICS
The q denotes the specifications which apply over the full operating temperature range of TJ = 25C.
PARAMETER Reference Reference Voltage Line Regulation Load Regulation Output Source Current Output Sink Current Regulator Supply Current CONDITIONS 4.5V VIN 36V 4.5V VIN 36V -2.0mA IREF 2mA, VIN = 12V VIN = 5V VIN = 5V VIN = 6V, IOUT 100A VIN = 36V, IOUT 100A VIN = 12V, IOUT = 125mA (VIN - VOUT) 1V, VIN 6V (VIN - VOUT) 1V, VIN 6V 6V VIN 36V IOUT = 100A IOUT = 125mA VIN = 12V VIN = 36V VIN = 36V VIN = 36V VIN = 36V VOUT = 29V, RL = 20k VIN = 4.5V VIN = 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 A A mA mA % %/V V V V nA A mA mV nA V/V mA A
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 TA -40C output sink current drops to 2.5mA.
TYPICAL PERFOR A CE CHARACTERISTICS
Regulator Load Regulation
0.3 PRE-LOAD = 100A TJ = -55C 100
SUPPLY CURRENT (mA)
TJ = 25C 0.1 0 TJ = 125C -0.1 -0.2 -0.3 0.1
10
SHORT-CIRCUIT CURRENT (mA)
OUTPUT VOLTAGE CHANGE (%)
0.2
1 100 10 OUTPUT CURRENT (mA)
UW
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 VOUT = 100mV MINIMUM LOAD CURRENT (A)
RIPPLE REJECTION (dB)
0.1
0.01 0.1 10 100 1 1000 REGULATOR OUTPUT CURRENT (mA)
1120A G04
Supply Current
10 IOUT = 100mA SUPPLY CURRENT (mA) 1
SUPPLY CURRENT (mA)
REFERENCE VOLTAGE CHANGE (mV)
0.1
IOUT = 10mA
IOUT = 1mA 0.01
VOUT = 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
TJ = -55C
OUTPUT CURRENT (mA)
TJ = 25C
TJ = 125C
4
UW
Regulator Minimum Load Current
100
70 65 60 55 50 45 40 35
Regulator Ripple Rejection
IOUT = 100mA
10
IOUT = 10mA IOUT = 1mA VIN = 10VDC, 1VP-P VOUT = 5V COUT = 10F 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 IOUT = 100mA 1
4 3 2 1 0 -1 -2 -3
Reference Regulation
0.1
IOUT = 10mA
IOUT = 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 VIN = 15V VOUT = 5V 0
Turn-On Characteristic
5.5 VOUT = 5V 5.0 NO LOAD 4.5 4.0 RL = 500 3.5 3.0 2.5 2.0 RL = 50 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. VOUT (Pin 4): Main output, requires 10F output capacitor. Can be shorted to VIN or ground without damaging device. VIN (Pin 5): Input Supply. Bypass with 10F 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.
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 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.
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REF 6 VIN 5
+
COMP OUT 7
100k
-
REF 2.5V 120k 3 1 8 -INPUT SHUTDOWN GROUND 4 2 VOUT 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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LT1 120A
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 20 should be used to isolate the capacitor from the reference pin. This 20 resistor can be placed directly in series with the capacitor or alternatively the reference line can have 20 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 6 OUTPUT 20 REF 6 20
+
10F
OR
+
OUTPUT 10F
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.
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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 10F is usually large enough to provide good stability. Increasing the output capacitor above 10F 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
TYPICAL APPLICATIO S
Regulator with Output Voltage Monitor
5 5V LOGIC LOGIC OUTPUT 500k 7 VIN OUTPUT 4 OUTPUT 5V 10F VOUT PIN 7
LOGIC OUTPUT GOES LOW WHEN VOUT DROPS BY 100mV
Compensating the Comparator as an Op Amp
VREF
6
+ -
7
IN
R2
1M C2 R1 C1
LT1120A GND 1
AV -1 -10 -100
R1 33 100 10k
C1 0.1F 0.047F 0.002F
C2 R2 0.001F 1M - 100k - 10k
BATTERY INPUT
5
VIN LT1120A GND 1
INTERNAL PARASITIC DIODES OF LT1120A VIN 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.
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-
LT1120A 8 2
+
0.001F 98k 2k 100k
1120A TA03
+
FEEDBACK REF 6 GND 1
LOGIC OUTPUT
Current Limited 1 Amp Regulator
2.2k 0.5* VIN MJE2955 2N3906* VOUT 5V AT 1A 220F 5 VIN 0.22F VOUT 4 FB 2 270 100k
50A
AT AV = 100, SLEW RATE = +0.05V/s - 6V/s
+
1M
* SETS CURRENT LIMIT BUT INCREASES DROPOUT VOLTAGE BY 0.5V.
MUST HAVE LOW
1120A TA04
ESR. SEVERAL 100F CAPACITORS CAN BE PARALLELED.
1120A TA06
Battery Backup Regulator
VOUT 5V VOUT FB 4 4
+
0.001F 2 50k 1M 1M 10F 2
VOUT LT1120A FB GND 1
VIN
5
MAIN POWER INPUT
1120A TA05
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LT1 120A
PACKAGE DESCRIPTIO
.300 - .325 (7.620 - 8.255)
.008 - .015 (0.203 - 0.381)
.065 (1.651) TYP .120 (3.048) .020 MIN (0.508) MIN .018 .003 (0.457 0.076)
(
+.035 .325 -.015 +0.889 8.255 -0.381
)
INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
NOTE: 1. DIMENSIONS ARE
.010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254)
.053 - .069 (1.346 - 1.752) 0- 8 TYP
.016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN
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)
.014 - .019 (0.355 - 0.483) TYP
RELATED PARTS
PART NUMBER LT1761/LT1762 LT1763 DESCRIPTION 100mA/150mA, Low Noise Micropower, LDO 500mA, Low Noise Micropower, LDO COMMENTS VIN: 1.8V to 20V; VOUT(MIN) = 1.22V; Dropout Voltage = 0.30V; IQ = 20A; ISD < 1A; VOUT = Adj, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V; ThinSOTTM/MS8 Packages. Low Noise <20VRMSP-P VIN: 1.8V to 20V; VOUT(MIN) = 1.22V; Dropout Voltage = 0.30V; IQ = 30A; ISD < 1A; VOUT = 1.5V, 1.8V, 2.5V,3V, 3.3V, 5V; SO-8 Package. Low Noise <20VRMSP-P VIN: 2.7V to 20V; VOUT(MIN) = 1.21V; Dropout Voltage = 0.34V; IQ = 1mA; ISD < 1A; VOUT = 1.8V, 2.5V, 3.3; DD, TO220, Packages. Low Noise <40VRMSP-P, "A" Version Stable with Ceramic Capacitors VIN: 1.8V to 20V; VOUT(MIN) = 1.22V; Dropout Voltage = 0.27V; IQ = 30A; ISD < 1A; VOUT = 1.5V, 1.8V, 2.5V,3V, 3.3V, 5V; MS8 Package. Low Noise <20VRMSP-P VIN: 2.1V to 20V; VOUT(MIN) = 1.21V; Dropout Voltage = 34V; IQ = 1mA; ISD < 1A; VOUT = 1.5V 1.8V, 2.5V, 3.3; DD, TO220, SOT-223, SO-8 Packages. Low Noise <40VRMSP-P, "A" Version Stable with Ceramic Capacitors VIN: -0.9V to -20V; VOUT(MIN) = -1.21V; Dropout Voltage = 0.34V; IQ = 30A; ISD < 3A; VOUT = Adj, -5V; ThinSOT Package. Low Noise <30VRMSP-P, Stable with Ceramic Capacitors VIN: 1.5V to 80V; VOUT(MIN) = 1.28V; Dropout Voltage = 0.30V; IQ = 30A; ISD < 1A; VOUT = Adj, -5V; MS8E Package. Low Noise <100VRMSP-P, Stable with Ceramic Capacitors
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LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDO LT1962 300mA, Low Noise Micropower, LDO
LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDO LT1964 200mA, Low Noise Micropower Negative, LDO LT3010 80V, 50mA, Low Noise Linear Regulator ThinSOT is a trademark of Linear Technology Corporation.
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
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N8 Package 8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.130 .005 (3.302 0.127) .400* (10.160) MAX 8 7 6 5 .045 - .065 (1.143 - 1.651) .255 .015* (6.477 0.381) 1 2 3 4
N8 1002
.100 (2.54) BSC
S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 - .197 (4.801 - 5.004) NOTE 3 .004 - .010 (0.101 - 0.254) 8 7 6 5 .045 .005 .050 BSC
.050 (1.270) BSC
.228 - .244 (5.791 - 6.197)
.150 - .157 (3.810 - 3.988) NOTE 3
.245 MIN
.160 .005
SO8 0303
.030 .005 TYP RECOMMENDED SOLDER PAD LAYOUT
1
2
3
4
LT/TP 0104 1K REV A * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 1994

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