LAB

SEME

IP1844 SERIES

IP1845 SERIES

Prelim. 2/95

DESCRIPTION

The IP1844 and IP1845 series of switching regulator control circuits contain all the functions necessary to

implement off-line, current mode switching regulators, using a minimum number of external parts.

Functions included are voltage reference, error amplifier, current sense comparator, oscillator, totem-pole output

driver and under-voltage lockout circuitry. In addition there is a toggle flip-flop which blanks the output on every

second clock pulse, thereby ensuring that the duty cycle never exceeds 50%.

Although pin compatible with the UC1844 and UC1845 series, SEMELAB has incorporated several improvements

in the IP1844 and IP1845 series allowing tighter and more complete specification of electrical performance .

BLOCK DIAGRAM

Values in brackets are for IP1845 series.

3.6V

ERROR

AMP

OSCILLATOR

2R

R

1V

R

S

PW M

LATCH

CURRENT

SENSE

COM PARATOR

16V

(8.4V)

6V

(0.5V)

2.5V

UNDER–VOLTAGE

LOCKOUT

ENABLE

REFERENCE

REGULATOR

5V

INTERNAL

BIAS

34V

REG

R

S

V

STATUS

LATCH

REF

T

Q

TOGGLE

FLIP

FLOP

PIN NUM BERS

1st Num ber

2nd Num ber

– N, J and 8 Pin D Packages

– 14 Pin D Package.

I

SENSE

/C

R

T

T

OUTPUT

POW ER

GROUND

V

REF

V

C

3/5

5/9

7/12

2/3

1/1

4/7

6/10

7/11

5/8

8/14

Supply Voltage

Output Current

Analog Inputs

(pins 2 and 3)

Error Amp Output Sink Current

IP1844 , IP1845

Operating Ambient Temperature Range

IP2844 , IP2845

IP3844 , IP3845

≤ 30V

0 to ±200mA

–0.3V to 3V

0 to 2mA

–55 to 125°C

–25 to 85°C

0 to 70°C

RECOMMENDED OPERATING CONDITIONS