Features: • Controls Zero Current Switched (ZCS) or Zero Voltage Switched (ZVS) Quasi-Resonant Converters
• Zero-Crossing Terminated One-Shot Timer
• Precision 1%, Soft-Started 5V Reference
• Programmable Restart Delay Following Fault
• Voltage-Controlled Oscillator (VCO) with Programmable Minimum and Maximum Frequencies from 10kHz to 1MHz
• Low Start-Up Current (150A typical)
• Dual 1 Amp Peak FET Drivers
• UVLO Option for Off-Line or DC/DC ApplicationsPinout
SpecificationsVCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 22V
Output Current
Source or Sink (Pins 11 & 14) . . . . . . . . . . . . . . . . . . . 0.5A
DC Pulse (0.5s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5A
Power Ground Voltage . . . . . . . . . . . . . . . . . . . . . . . ±0.2V
Inputs (Pins 2, 3, 10, & 15) . . . . . . . . . . . . . . . . 0.4 to 7V
Error Amp Output Current . . . . . . . . . . . . . . . . . . . . ±2mA
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W
Junction Temperature (Operating). . . . . . . . . . . . . . 150°C
Lead Temperature (Soldering, 10 seconds) . . .. . . . 300°C
All voltages are with respect to signal ground and all currents are positive into the specified terminal. Pin numbers refer to the J and N packages. Consult Unitrode Integrated Circuits databook for information regarding thermal specifications and limitations of packages.
DescriptionThe UC3861-3868 family of ICs is optimized for the control of Zero Current Switched and Zero Voltage Switched quasi-resonant converters. Differences between members of this device family result from the various combinations of UVLO thresholds and output options. Additionally, the one-shot pulse steering logic is configured to program either on-time for ZCS systems (UC1865-1868), or off-time for ZVS applications (UC1861- 1864).
UC3861-3868,The primary control blocks implemented include an error amplifier to compensate the overall system loop and to drive a voltage controlled oscillator (VCO), featuring programmable minimum and maximum frequencies. Triggered by the VCO, the one-shot generates pulses of a programmed maximum width, which can be modulated by the Zero Detection comparator. This circuit facilitates "true" zero current or voltage switching over various line, load, and temperature changes, and is also able to accommodate the resonant components' initial tolerances.
UC3861-3868,Under-Voltage Lockout is incorporated to facilitate safe starts upon power-up. The supply current during the under-voltage lockout period is typically less than 150A, and the outputs are actively forced to the low state.
UC3861-3868 Data Sheet
