Advanced Monolithic Systems, Inc.

6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140

LP2950/LP2951

2 Ampere Low Dropout Regulator

Regulator with Early Warning and Auxiliary Output

ERROR

ERROR

FLAG

CURRENT

LIMIT SECTION

GND

FB

V

OUT

SD

1

4

3

8

5

7

+V

IN

+V

LP2951

+V

R

1

R

2

10k

Ω

100

µF

4.7

TANT.

+

+

1%

220

.033

20k

Ω

4.7M

Ω

2N3906

0.05

680

470

MJE2955

ERROR

GND

FB

V

OUT

5

4

8

1

6

+V

IN

LP2951

#1

V

TAP

7

ERROR

GND

FB

V

OUT

4

8

6

+V

IN

LP2951

#2

V

TAP

3

SD

7

SENSE

2

5

RESET

1

µF

20

+V

IN

D

1

D

2

3.6V

NICAD

27 k

Ω

2.7M

Ω

330 k

Ω

1

µF

D

4

Q

1

MAIN 5V OUTPUT

µP

V

DD

2

D

3

5V MEMORY

SUPPLY

EARLY WARNING

SENSE

+

+

VOUT = 1.23V(1+R1/R2)

•

Early warning flag on low input voltage

•

Main output latches off at lower input voltages

•

Battery backup on auxiliary output

≤ 5.7V. When V

exceeds 5.7V Reg.#1 is back in regulation and the early warning signal rises,

unlatching Reg.#2 via D3.

1A Regulator with 1.2V Dropout

Latch Off When Error Flag Occurs

OUTPUT

5V ± 1% @

0 TO 1A

GND

FB

OUT

IN

4

7

6

1

2

8

V

TAP

LP2951

SUPERTEX

VP12C

SENSE

0.002µF

2kΩ

10kΩ

1ΜΩ

0.01µF

220µF

1µF

+

I

UNREGULATED

INPUT

R

1

ERROR

GND

FB

V

OUT

R

2

SD

7

4

3

8

1

5

+V

IN

+V

IN

V

OUT

1

µF

+

470k

Ω

LP2951

470k

Ω

RESET