LAB

SEME

IP1844A SERIES

IP1845A SERIES

Prelim. 2/95

Output Current

Analog Inputs

(pins 2 and 3)

Error Amp Output Sink Current

IP1844A , IP1845A

Operating Ambient Temperature Range

IP2844A , IP2845A

IP3844A , IP3845A

≤ 30V

0 to ±200mA

–0.3V to 3V

0 to 2mA

–55 to 125°C

–25 to 85°C

0 to 70°C

Notes:

1.

Lower limit set by under voltage lockout specification.

RECOMMENDED OPERATING CONDITIONS

* 1844A and 1845A series only.

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

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

TOGGLE

FLIP

FLOP *

T

Q

DESCRIPTION

The IP1844A/IP1845A 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 the IP1844A and IP1845A series of devices have a toggle flip-flop which blanks the output on every

second clock pulse, thereby ensuring that the duty cycle never exceeds 50%. For applications requiring more

flexible control, all devices feature an on-chip trimmed oscillator discharge current, allowing accurate control to

maximum-duty-cycle by selection of timing components. This can be beneficial even when using the IP1844A or

IP1845A series, as it allows optimum safety margins to be designed into the application.

Although pin compatible with the standard IP1844/5 parts these devices offer improved performance in several

areas. They also offer tighter specification and improved performance over the IP and UC1844/5 series, whilst

retaining complete compatibility.

BLOCK DIAGRAM