Low power current mode push-pull PWM with discharge transistor, 12.5/8.3V UVLO, -40°C to 85°C

The UCCx808A devices are a family of

BiCMOS push-pull, high-speed, low-power, pulse-width modulators. The UCCx808A

contain all of the control and drive circuitry required for off-line or DC-to-DC

fixed frequency current-mode switching power supplies with minimal external parts

count.

The

UCCx808A 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, thus limiting each output stage duty cycle to

less than 50%.

The UCCx808A family offers a variety

of package options, temperature range options, and choice of undervoltage lockout

levels. The family has UVLO thresholds and hysteresis options for offline and

battery-powered systems.

The UCCx808A are an enhanced version

of the UCC3808 family. The significant difference 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 feature discharges any filter

capacitance on the CS pin during each cycle, and helps minimize filter capacitor

values and current sense delay.