Datasheet

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LT1120

1120fc

TYPICAL APPLICATIO

APPLICATIO S

FEATURES

DESCRIPTIO

Micropower Regulator with

Comparator and Shutdown

The LT

1120 is a combination micropower positive regu-

lator and free collector comparator on a single monolithic

chip. With only 40µA supply current, the LT1120 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. 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.

The 2.5V reference will source or sink current. This allows

it to be used as a supply splitter or auxiliary output.

■

40µA Supply Current

■

125mA Output Current

■

2.5V Reference Voltage

■

Reference Output Sources 2mA and Sinks 2mA

■

Open Collector Comparator Sinks 10mA

■

Logic Shutdown

■

0.2V Dropout Voltage

■

Thermal Limiting

■

Available in 8-Lead DIP and SO Packages

■

Battery Systems

■

Battery-Backup System

■

Portable Terminals

■

Portable Instruments

■

Memory Keep-Alive

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

5V Regulator

Dropout Voltage and Supply Current

OUTPUT CURRENT (mA)

0.1 1

0.01

DROPOUT VOLTAGE (V)

SUPPLY CURRENT (mA)

0.10

1.00

0.1

10 100 1000

1120 TA02

+ +

OUT

GNDSHDN

SHUTDOWN

LT1120

0.001µF1M

25µF

> 5.2V

= 40µA

1120 TA01

10µF

Summary of content (12 pages)

PAGE 1
LT1120 Micropower Regulator with Comparator and Shutdown U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT®1120 is a combination micropower positive regulator and free collector comparator on a single monolithic chip. With only 40µA supply current, the LT1120 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
LT1120 W W U W ABSOLUTE AXI U RATI GS (Note 1) Input Voltage ........................................................... 36V NPN Collector Voltage ............................................. 36V Output Short-Circuit Duration .......................... Indefinite Power Dissipation ............................... Internally Limited Operating Temperature Range LT1120C ................................................ 0°C to 100°C LT1120I ................................................
PAGE 3
LT1120 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Tj = 25°C. PARAMETER CONDITIONS Feedback Sense Voltage VIN = 12V Shutdown Pin Voltage TYP MAX 2.44 2.5 2.56 V 0.4 V Normal VOUT ≤ 0.5V Shutdown Pin Current MIN Shutdown 2.2 VIN = 1.4V Feedback Bias Current UNITS 1.
PAGE 4
LT1120 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS MIN TYP MAX UNITS Comparator Offset Voltage ● Bias Current VIN = 36V (Note 2) ● Gain ∆VOUT = 29V, RL = 20k ● 1000 Output Sink Current VIN = 4.5V (Note 3) ● 5 Leakage Current VIN = 36V ● Note 1: Absolute Maximum Ratings are those values beyond which the life a device may be impaired.
PAGE 5
LT1120 U W TYPICAL PERFOR A CE CHARACTERISTICS Supply Current Supply Current at Dropout 10 10 TJ = –55°C TO 125°C SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) IOUT = 100mA 1 IOUT = 10mA 0.1 IOUT = 1mA IOUT = 100mA 1 IOUT = 10mA 0.1 IOUT = 1mA VOUT = 5V TJ = –55°C TO 125°C 0.01 0.01 1 5 10 15 20 25 REGULATOR INPUT-OUTPUT DIFFERENTIAL (V) 1 0.1 0.2 0.3 0.4 0.5 0.
PAGE 6
LT1120 U U U PI FU CTIO S GND (Pin 1): Ground. VIN (Pin 5): Input Supply. Bypass with a 10µF capacitor. Must always be more positive than ground. FB (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. REF (Pin 6): Reference. 2.5V can source or sink current. May be shorted to ground or up to 5V.
PAGE 7
LT1120 U U W U APPLICATIO S I FOR ATIO Reference Overload Protection Internal to the LT1120 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 typically 4mA or 5mA and sink 2mA. The available source and sink current decreases as temperature increases.
PAGE 8
LT1120 U TYPICAL APPLICATIO S Regulator with Output Voltage Monitor 5 5V VIN LT1120 VOUT 4 VOUT 5V 500k LOGIC LOGIC OUTPUT 0.001µF – 7 98k VOUT –INPUT 8 + + FB REF 6 PIN 7 10µF 2k LOGIC OUTPUT 2 GND 100k 1 1120 TA03 LOGIC OUTPUT GOES LOW WHEN VOUT DROPS BY 100mV 1A Low Dropout Regulator Compensating the Comparator as an Op Amp VIN 6 8 50µA + 7 2.2k – AT Av = 100, SLEW RATE = +0.
PAGE 9
LT1120 U TYPICAL APPLICATIO S Regulator with Improved Transient Response 5V Regulator 5 VIN > 5.2V IQ = 40µA VIN VOUT 4 5V 0.001µF LT1120 + 10µF FB 5 VIN > 5.2V VIN 1M 4 5V 0.001µF LT1120 + 2 VOUT FB 25µF GND + 25µF 0.001µF GND 1M 1 1M 2 1 22k 1120 TA06 1M 1120 TA07 Battery-Backup Regulator VOUT 5V 5 BATTERY INPUT VIN VOUT 4 4 + 0.
PAGE 10
R1 25Ω Q7 Q6 R36 60k Q8 Q9 R2 50k Q12 Q10 R37 110.8k R3 50k Q11 8 –INPUT Q17 Q18 Q15 Q16 Q14 R35 42k R6 3k Q21 Q19 R7 6.
PAGE 11
LT1120 U PACKAGE DESCRIPTIO H Package 8-Lead TO-5 Metal Can (.230 Inch PCD) (Reference LTC DWG # 05-08-1321) .335 – .370 (8.509 – 9.398) DIA .027 – .045 (0.686 – 1.143) .305 – .335 (7.747 – 8.509) 45°TYP .040 (1.016) MAX .050 (1.270) MAX SEATING PLANE GAUGE PLANE .010 – .045* (0.254 – 1.143) PIN 1 .028 – .034 (0.711 – 0.864) .165 – .185 (4.191 – 4.699) .230 (5.842) TYP REFERENCE PLANE .500 – .750 (12.700 – 19.050) H8 (TO-5) 0.230 PCD 0801 .110 – .160 (2.794 – 4.064) INSULATING STANDOFF .
PAGE 12
LT1120 U TYPICAL APPLICATIO Current Limited 1A Regulator 0.5Ω* VIN 2.2k MJE2955 2N3906* 5 VIN VOUT 5V AT 1A VOUT 4 0.22µF LT1120 FB 100k + 2 220µF† GND 1 270Ω 100k 1120 TA10 * SETS CURRENT LIMIT BUT INCREASES DROPOUT VOLTAGE BY 0.5V † MUST HAVE LOW ESR. SEVERAL 100µF CAPACITORS CAN BE PARALLELED U PACKAGE DESCRIPTIO 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 – .