LT1185 查看數據表（PDF） - Linear Technology

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LT1185

Low Dropout Regulator

Linear Technology 

LT1185

TYPICAL APPLICATIO S

Low Input Voltage Monitor Tracks Dropout Characteristics

+

+ C2

2.2µF

TANT

VIN

R5*

0.01Ω

–

R3

360k

R4**

1k

4k

REF

GND

FB

VIN

LT1185

VOUT

+

R1

2.37k

+

R2

2.6k

C1

2.2µF VOUT

TANT

–

*3" #26 WIRE

**R4 DETERMINES TRIP POINT AT IOUT = 0

R6 DETERMINES INCREASE OF TRIP POINT AS IOUT INCREASES

( ) TRIP POINT FOR VIN = VOUT

1

+

R4

R3

•

•

R7

R6

+

IOUT

R5 • R7

R6

FOR VALUES SHOWN, TRIP POINT FOR VIN IS:

VOUT + 0.37V AT IOUT = 0 AND VOUT = 1.18V AT IOUT = 3A

†DO NOT SUBSTITUTE. OP AMP MUST HAVE COMMON MODE

RANGE EQUAL TO NEGATIVE SUPPLY

R6**

1k

R7

27k

OPTIONAL HYSTERESIS

≈2M

3+

2

LT1006† V+

– V– 7

4

LT1185 • TA05

“LOW” FOR LOW INPUT

OUTPUT SWINGS FROM VIN+ TO VIN–

Time Delayed Start-Up

+

D3†

R3**

15k D2

RLIM***

+

R1

2.37k

VIN

+

–

C2

2.2µF

Q1**

C3*

D1

REF

GND

FB

VIN

LT1185

+ C1

VOUT

2.2µF

TANT

R2

VOUT

–

ALL DIODES 1N4148

LT1185 • TA06

*SEE CHART FOR DELAY TIME VERSUS (C3)(R3//RLIM) PRODUCT

**FOR LONG DELAY TIMES, REPLACE D2 WITH 2N3906 TRANSISTOR AND USE R3 ONLY FOR

CALCULATING DELAY TIME. R3 CAN INCREASE TO 100k

***ILIM IS ≈11k/RLIM, INSTEAD OF 15k, BECAUSE OF VOLTAGE DROP IN D1. TEMPERATURE

COEFFICIENT OF ILIM WILL BE ≈0.11%/°C, SO ADEQUATE MARGIN MUST BE ALLOWED

FOR COLD OPERATION

†D3 PROVIDES FAST RESET OF TIMING. INPUT MUST DROP TO A LOW VALUE TO RESET TIMING

12

Delay Time

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

0

5 10 15 20 25 30

INPUT VOLTAGE (V)

LT1185 • TA07

( ) *t = (R3//RLIM)(C3) =

R3 • RLIM

R3 + RLIM

(C3)

1185ff

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