9

LT1431

TYPICAL APPLICATIO S

0

0

1

2

3

4

6

1

23

4

LT1431 • TA14

56

5

5V Power Supply Monitor with

±500mV

Window and 50mV Hysteresis

Transfer Function

High Efficiency Buck Converter E = 85% to 89%

6

5

C2

4.7

µF 35V

TANTALUM

GND

FB

LT1170

C3

0.1

µF

D2

BAT85

D1

BAT85

C1

220

µF

35V

R4

100

Ω

R2

1k

R6*

23.7k

R7*

24.9k

Q1

VN2222LL

C5

0.047

µF

5

4

2

1

3

C4

0.033

µF

D4

BAT85

D3

MBR330

L1

50

µH 3A

C6

470

µF

16V

1

3

4

8

7

R8*

24.9k

VIN

OFF

RTN

1

2

R3

10k

NOTES: UNLESS OTHERWISE SPECIFIED

1. ALL RESISTANCES ARE IN

Ω, 0.25W, 5%

2. ALL CAPACITANCES ARE IN

µF, 50V, 10%

3. SHUTDOWN LOGIC STATE MUST BE DEFINED BY A LOGIC GATE OR BY TYING TO GND

5V

2.5A

R1

470k

R5

680

Ω

Q3

2N3904

+

0.12m

Ω

ESR

RUN = 0

SHUTDOWN

> 3V

1

BOLD LINE INDICATES HIGH CURRENT PATHS

* = 1% FILM RESISTORS

C1 = NICHICON-UPL1V221MPH

C6 = NICHICON-UPL1C471MPH6

D1, D2 = PHILIPS-BAT85

D3 = MOTORALA-MBR330

L1 = COILTRONICS CTX50-3-MP

C3, C4, C5 = WIMA-MKS-2

2

Q2

2N3904

V +

COLL

REF

COMP

VR2

LT1431CN8

+

GND-F

GND-S

+

LT1431 • TA15

COLL

REF

GND-F

GND-S

10

Ω**

“HIGH” FOR

OVER VOLTAGE OR

UNDER VOLTAGE

5k

1N4148

COLL

REF

GND-F

GND-S

10

Ω**

5k

4k*

1k

6k*

1k

*DETERMINES WINDOW SIZE

V = (R – 5)(0.5mA)

**SETS HYSTERESIS

LT1431 • TA13

LT1431

LT1431