CM3842 datasheet(2/12 Pages) ETC | CURRENT MODE PWM CONTROLLER

2 page

CM3842/3843

CURRENT MODE PWM CONTROLLER

2001/06/27

Advanced

Champion Microelectronic Corporation

Page 1

GENERAL DESCRIPTION

FEATURES

The CM3842/43 are fixed frequency current-mode PWM

controllers specially designed for OFF-Line switching

power supply and DC-to-DC converters with a minimum

number of external components. These devices feature

a trimmed oscillator for precise duty cycle control, a

temperature compensated reference, high gain error

amplifier, current sensing comparator, and high current

totem

pole

output

which

suitable

for

driving

MOSFETs.

The under voltage lock-out (U.V.L.O.) is designed to

operated with 200

µA typ. start-up current, allowing an

efficient bootstrap supply voltage design. The U.V.L.O.

thresholds for the CM3842 are 16V (on) and 10V (off)

which

are

ideal

for

off-line

applications.

The

corresponding typical threshold for the CM3843 are

8.4V (on) and 7.6V (off). The CM3842/43 can operated

within 100% duty cycle.

Low Start-Up current ( typ. 200

µA)

Optimized for Off-Line and DC-to-DC Converters

Maximum Duty Cycle

U.V.L.O. with Hysteresis

Operating Frequency Up to 500KHz

Internal Trimmed Bandgap Reference

High Current Totem Pole Output

Error Amplifier With Low Output Resistance

Available in 8-Pin Plastic DIP and Surface Mount

8-Pin S.O.I.C.

APPLICATIONS

PIN CONFIGURATION

Off-line flyback or forward converters.

DC-to-DC buck or boost converter.

Monitor Power Supply

8-Pin PDIP

(Top View)

AVAILABLE OPTIONS

Device

Start-UP

Voltage

Hysteresis Max. Duty Cycle

CM3842

16V

< 100%

CM3843

8.4V

0.8V

< 100%

8-Pin S.O.I.C.

(Top View)

COMP

VFB

ISENSE

VREF

GND

OUTPUT

VCC

RT/CT

COMP

VFB

ISENSE

VREF

GND

OUTPUT

VCC

RT/CT

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