UC3845B:Current Mode PWM

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.

Key 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
Product Specifications
DescriptionVersionSize
DS0908: High performance current mode PWM controller3.3233 KB
Application Notes
DescriptionVersionSize
AN246: UC3842 provides low-cost current mode control1.31 MB
Presentations
DescriptionVersionSize
Primary side regulation controllers portfolio1 MB
Brochures
DescriptionVersionSize
Brochure Power management guide05.20164 MB
Sample & Buy
Part NumberPackagePacking TypeUnit Price (US$) *QuantityECCN (EU)ECCN (US)Country of Origin
UC3845BNDIP-8Tube--NECEAR99-
UC3845BD1SO-8Tube--NECEAR99MOROCCO
UC3845BD1013TRSO-8Tape And Reel--NECEAR99MOROCCO
Quality & Reliability
Part NumberPackageGradeRoHS Compliance GradeMaterial Declaration**
UC3845BNDIP-8IndustrialEcopack2
UC3845BD1SO-8IndustrialEcopack2md_o7-wspc-so-wspc-08-wspc-.15-wspc-jedec_mjo7l127ea6-wspc-(uc3845bd1013tr)_a_ver2_signed.pdf
UC3845BD1013TRSO-8IndustrialEcopack2md_o7-wspc-so-wspc-08-wspc-.15-wspc-jedec_mjo7l127ea6-wspc-(uc3845bd1013tr)_a_ver2_signed.pdf
High performance current mode PWM controller UC3842B
circuit_diagram_4299_thumbnail.png UC3842B
UC3842 provides low-cost current mode control UC3842B
48 V - 130 W high efficiency converter with PFC for LED street lighting applications - European version L6599AT
Very low drop voltage regulators with inhibit KFXX
md_o7-wspc-so-wspc-08-wspc-.15-wspc-jedec_mjo7l127ea6-wspc-(uc3845bd1013tr)_a_ver2_signed.pdf UC3845B