The UCC3580 family of PWM controllers is designed to implement a varietyof active clamp/reset and synchronous rectifier switching converter topologies.While containing all the necessary functions for fixed frequency, highperformance pulse width modulation, the additional feature of this design isthe inclusion of an auxiliary switch driver which complements the mainpower switch, and with a programmable deadtime or delay between eachtransition. The active clamp/reset technique allows operation of singleended converters beyond 50% duty cycle while reducing voltage stresseson the switches, and allows a greater flux swing for the power transformer.This approach also allows a reduction in switching losses by recovering energystored in parasitic elements such as leakage inductance and switchcapacitance.
The oscillator is programmed with two resistors and a capacitor to setswitching frequency and maximum duty cycle. A separate synchronizedramp provides a voltage feedforward pulse width modulation and a programmedmaximum volt-second limit. The generated clock from the oscillatorcontains both frequency and maximum duty cycle information.
The main gate drive output (OUT1) is controlled by thepulse width modulator. The second output (OUT2) is intendedto activate an auxiliary switch during the off timeof the main switch, except that between each transitionthere is deadtime where both switches are off, programmedby a single external resistor. This design offerstwo options for OUT2, normal and inverted. In the -1 and-2 versions, OUT2 is normal and can be used to drivePMOS FETs. In the -3 and -4 versions, OUT2 is invertedand can be used to drive NMOS FETs. In all versions,both the main and auxiliary switches are held off prior tostartup and when the PWM command goes to zero dutycycle. During fault conditions, OUT1 is held off whileOUT2 operates at maximum duty cycle with a guaranteedoff time equal to the sum of the two deadtimes.
Undervoltage lockout monitors supply voltage (VDD), theprecision reference (REF), input line voltage (LINE), andthe shutdown comparator (SHTDWN). If after any ofthese four have sensed a fault condition, recovery to fulloperation is initiated with a soft start. VDD thresholds, onand off, are 15V and 8.5V for the -2 and -4 versions, 9Vand 8.5V for the -1 and -3 versions.
The UCC1580-x is specified for operation over the militarytemperature range of -55°C to 125°C. TheUCC2580-x is specified from -40°C to 85°C. TheUCC3580-x is specified from 0°C to 70°C. Package optionsinclude 16-pin surface mount and dual in-line.
Provides Auxiliary Switch Activation Complementary to Main Power Switch Drive
Programmable deadtime (Turn-on Delay) Between Activation of Each Switch
Voltage Mode Control with Feedforward Operation
Programmable Limits for Both Transformer Volt- Second Product and PWM Duty Cycle
High Current Gate Driver for Both Main and Auxiliary Outputs
Multiple Protection Features with Latched Shutdown and Soft Restart
Low Supply Current (100 A Startup, 1.5 mA Operation)