Product overview

Description

The UC284xB family of control ICs provides the necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. Internally implemented circuits include a trimmed oscillator for precise DUTY CYCLE CONTROL under voltage lockout featuring start-up current less than 0.5mA, a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM comparator which also provides current limit control, and a totem pole output stage designed to source or sink high peak current. The output stage, suitable for driving N-Channel MOSFETs, is low in the off-state.

Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle ranges. The UC2842B and UC2844B have UVLO thresholds of 16V (on) and 10V (off), ideally suited off-line applications The corresponding thresholds for the UC2843B and UC2845B are 8.5V and 7.9V. The UC2842B and UC2843B can operate to duty cycles approaching 100%. A range of the zero to < 50 % is obtained by the UC2844B and UC2845B by the addition of an internal toggle flip flop which blanks the output off every other clock cycle.

  • All features

    • LOW START-UP AND OPERATING CURRENT
    • UNDERVOLTAGE LOCKOUT WITH HYSTERESIS
    • INTERNALLY TRIMMED REFERENCE WITH UNDERVOLTAGE LOCKOUT
    • CURRENT LIMITING
    • TRIMMED OSCILLATOR FOR PRECISE FREQUENCY CONTROL
    • CURRENT MODE OPERATION TO 500kHz
    • OSCILLATOR FREQUENCY GUARANTEED AT 250kHz
    • LATCHING PWM FOR CYCLE-BY-CYCLE
    • HIGH CURRENT TOTEM POLE OUTPUT
    • AUTOMATIC FEED FORWARD COMPENSATION

Circuit Diagram

The current status of a product:
Active: Product is in volume production
Evaluation: Product is under characterization. Limited Engineering samples available
Preview: Product is in design stage
Target: Product is in design feasibility stage.No commitment taken to produce
Proposal: Marketing proposal for customer feedback.No commitment taken to design or produce
NRND: Not Recommended for New Design.Product is in volume production only to support customers ongoing production.
Marketing description of the package type.Compliancy of the device with industry requirement domains (IRD)The RoHS status of a product:
ECOPACK 1: Initial grade to identify European RoHS compliant products.
ECOPACK 2: New grade to identify brominated chlorinated and antimony oxide flame retardant free products.
ECOPACK 3: Halogen free RoHS exemptions free products.
(*): ECOPACK 2 version available upon request.
(**): Some versions still existing in ECOPACK 1 or not compliant.
The current status of a product:
Active: Product is in volume production
Evaluation: Product is under characterization. Limited Engineering samples available
Preview: Product is in design stage
Target: Product is in design feasibility stage.No commitment taken to produce
Proposal: Marketing proposal for customer feedback.No commitment taken to design or produce
NRND: Not Recommended for New Design.Product is in volume production only to support customers ongoing production.
Budgetary PriceMarketing description of the package type.Storage method used to contain product.Main country of assembly or fabrication of the product.ECCNs are five character alpha-numeric designations used on the Commerce Control List to identify dual-use items for export control purposes. ECCNs are five character alpha-numeric designations used on the Commerce Control List to identify dual-use items for export control purposes.The value as specified by level (minTypMax) of the ambient temperature (in Cel) in which this item was designed to operate.The value as specified by level (minTypMax) of the ambient temperature (in Cel) in which this item was designed to operate.