UCC1570

Features:

` Low Power BiCMOS Process
` 85A Start-up Current
` 1mA Run Current
` 1A Peak Gate Drive Output
` Voltage Feed Forward
` Programmable Duty Cycle Clamp
` Optocoupler Interface
` 500kHz Operation
` Soft Start
` Fault Counting Shutdown
` Fault Latch Off or Automatic Restart


Pinout




Specifications

Supply Voltage
(Limit Supply Current to 20mA) . . . . . . . Self Limiting at 15V
Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . .   . . +20mA
Analog Inputs (CURLIM, VFWD, FEEBK) . . . . . . . . . . .. . .. 6V
Programming Current ISLOPE, IISET . . . . . . . . . . . .. . 1mA
Output Current IOUT
DC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . ±180mA
Pulse (0.5ms) . . . . . . . . . . . . . . . . . . . . . . . .. . .  . . . . ±1.2A


Description

The UCC1570 family of pulse width modulators is intended for application in isolated switching supplies using primary side control and a voltage mode feedback loop. Made with a BiCMOS process, these devices feature low startup current for efficient off-line starting with a bootstrapped low voltage supply. Operating current of UCC1570 is also very low; yet these devices maintain the ability to drive a power MOSFET gate at frequencies above 500kHz.

Voltage feedforward of UCC1570 provides fast and accurate response to wide line voltage variation without the noise sensitivity of current mode control. Fast current limiting is included with the ability to latch off after a programmable number of repetitive faults has occurred. This allows the power supply to ride through a temporary overload, while still shutting down in the event of a permanent fault. Additional versatility of UCC1570  is provided with a maximum duty cycle clamp programmable within a 20% to 80% range and line voltage sensing with a programmable window of allowable operation.