Datasheet

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LT1120A

1120afa

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20µA Supply Current

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125mA Output Current

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2.5V Reference

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Reference Output Sources 4mA and Sinks 4mA

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Open Collector Comparator Sinks 10mA

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Logic Shutdown

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0.2V Dropout Voltage

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Thermal Limiting

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8-Lead SO Package

The LT

1120A is a combination micropower positive

regulator and free collector comparator on a single mono-

lithic 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 cur-

rents. 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 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.

Micropower Regulator with

Comparator and Shutdown

Dropout Voltage and Supply Current5V Regulator

1120A TA01

> 5.2V

= 20µA

10µF

SHUTDOWN

0.001µF

25µF

LT1120A

OUT

GND

OUTPUT CURRENT (mA)

0.1

0.01

DROPOUT VOLTAGE (V)

1.00

1 1000

1120A TA02

0.10

100

0.1

SUPPLY CURRENT (mA)

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Battery Systems

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Battery Backup System

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Portable Terminals

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Portable Instruments

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Memory Keep Alive

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

, LTC and LT are registered trademarks of Linear Technology Corporation.

Summary of content (8 pages)

PAGE 1
LT1120A Micropower Regulator with Comparator and Shutdown U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ 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.
PAGE 2
LT1120A U U W W W 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 .............
PAGE 3
LT1120A ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range of TJ = 25°C.
PAGE 4
LT1120A U W 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.
PAGE 5
LT1120A U U U 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.
PAGE 6
LT1120A U U W U 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.
PAGE 7
LT1120A U 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.
PAGE 8
LT1120A U 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.