IP1844A 데이터 시트보기 (PDF) - Semelab - > TT Electronics plc

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IP1844A

CURRENT MODE REGULATING PULSE WIDTH MODULATORS

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SEME

LAB

IP1844A SERIES

IP1845A SERIES

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

VCC7/12

GND 5/9

34V

16V

(8.4V)

UNDER–VOLTAGE

LOCKOUT

ENABLE

REFERENCE 5V

REGULATOR

6V

(0.5V) 2.5V

REG

INTERNAL

BIAS

8 /1 4

VREF

S

VREF STATUS

LATCH

R

7/11 VC

R T /CT 4/7

VFB 2/3

COMP 1/1

ISENSE 3/5

OSCILLATOR

ERROR

AMP

2R

R

3.6V

6 /1 0

OUTPUT

Q

T

TOGGLE

FLIP

FLOP *

5/8 POW ER

GROUND

S

1V

R

PWM

LATCH * 1844A and 1845A series only.

CURRENT

Values in brackets are for IP1845 series.

SENSE

COMPARATOR

PIN NUMBERS

1st Number – N, J and 8 Pin D Packages

2nd Num ber – 14 Pin D Package.

RECOMMENDED OPERATING CONDITIONS

VCC

Supply Voltage 1

IO

Output Current

Analog Inputs

(pins 2 and 3)

Error Amp Output Sink Current

Notes:

Operating Ambient Temperature Range

IP1844A , IP1845A

IP2844A , IP2845A

IP3844A , IP3845A

1. Lower limit set by under voltage lockout specification.

Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.

≤ 30V

0 to ±200mA

–0.3V to 3V

0 to 2mA

–55 to 125°C

–25 to 85°C

0 to 70°C

Prelim. 2/95

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