Enhanced Product Low Power Current Mode Push-Pull PWM

The UCC2808A-xEP is a family of BiCMOS push-pull, high-speed, low-power, pulse-width modulators. The UCC2808A-xEP contains all of the control and drive circuitry required for off-line or DC/DC fixed frequency current-mode switching power supplies with a minimal external parts count.

The UCC2808A-xEP dual output drive stages are arranged in a push-pull configuration. Both outputs switch at half the oscillator frequency using a toggle flip-flop. The dead time between the two outputs is typically 60ns to 200ns, depending on the values of the timing capacitor and resistors. The output stage duty cycle is limited to less than 50%.

The UCC2808A-xEP family offers a variety of package options and choice of undervoltage lockout levels. The family has UVLO thresholds and hysteresis options for off-line and battery-powered systems. Thresholds are shown in Device Comparison Table.

The UCC2808A-xEP is an enhanced version of the UCC2808 family. The significant difference between families is that the A versions feature an internal discharge transistor from the CS pin to ground, which is activated each clock cycle during the oscillator dead time. The internal discharge transistor discharges any filter capacitance on the CS pin during each cycle and helps minimize filter capacitor values and current-sense delay.