CM3843

Features:

`Low Start-Up current ( typ. 200A)
`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.


Application

· Off-line flyback or forward converters.
· DC-to-DC buck or boost converter.
·Monitor Power Supply



Pinout




Specifications

Supply voltage, VCC	35V
Output current, IO	± 1A
Analog inputs, VI	-0.3V to 6.3V
Error amp output sink current, ISINK(EA)	10mA
Power dissipation (TA = 25 ), PD	1W
Maximum junction temperature TJ	150
Storage temperature range	-65 to 150
Lead temperature (soldiering, 10 seconds)	260

Description

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 is suitable for driving MOSFETs.
The under voltage lock-out (U.V.L.O.) CM3843 is designed to operated with 200A 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.