UC3842 Philips Current-mode PWM controller Data Sheet

Description

The UC3842 is available in an 8-Pin mini-DIP the necessary features to implement off-line, fixed-frequency current-mode control schemes with a minimal external parts count. This technique results in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting.
Protection circuitry includes built-in undervoltage lock-out and current limiting. Other features include fully-latched operation, a 1% trimmed bandgap reference, and start-up current less than 1mA.
These devices feature a totem-pole output designed to source and sink high peak current from a capacitive load, such as the gate of a power MOSFET. Consistent with N-channel power devices, the output is low in the OFF-state.

FEATURES
– Low start-up current
– Automatic feed-forward compensation
– Pulse-by-pulse current limiting
– Enhanced load response characteristics
– Undervoltage lock-out with hysteresis
– Double pulse suppression
– High current totem-pole output
– Internally-trimmed bandgap reference
– 400kHz operation, guaranteed min

DATASHEET CONTAINS:

PIN CONFIGURATIONS (UC3842 PINOUT)

APPLICATIONS
– Off-line switched mode power supplies
– DC-to-DC converters UC3842

BLOCK DIAGRAM

ORDERING INFORMATION

ABSOLUTE MAXIMUM RATINGS

DC AND AC ELECTRICAL CHARACTERISTICS
– Reference section
– Oscillator section
– Error amp section
– Current sense section
– Output section
– Undervoltage lockout section
– PWM section
– Total standby current
– Maximum operating frequency section

UNDERVOLTAGE LOCKOUT

ERROR AMP CONFIGURATION

CURRENT SENSE CIRCUIT

TYPICAL PERFORMANCE CHARACTERISTICS
– Output Saturation Characteristics
– Error Amplifier Open-Loop Frequency Response

OPEN-LOOP LABORATORY TEST FIXTURE

SHUTDOWN TECHNIQUES

OFF-LINE FLYBACK REGULATOR

SPECIFICATIONS

SYNCHRONIZATION AND MAXIMUM DUTY CYCLE CLAMP

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