UCC2808ADTR-2

The UCCx808A devices are a series of BiCMOS push-pull high-speed, low-power pulse-width modulators. The UCCx808A incorporates all the control and drive circuitry required for off-line or DC/DC fixed-frequency current-mode switching power supplies while minimizing the number of external components. The dual-output driver stage of the UCCx808A is 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 from 60 ns to 200 ns, depending on the values of the timing capacitor and resistor, thus limiting the duty cycle of each output stage to less than 50%. The UCCx808A series offers various package options and temperature range options and supports the selection of undervoltage lockout levels. This series of devices has UVLO thresholds and hysteresis options suitable for off-line and battery-powered systems. The UCCx808A is an enhanced version of the UCC3808 series. The major difference between them is that the A version uses an internal discharge transistor between the CS pin and ground, which remains active during each clock cycle within the oscillator dead time. This feature discharges any filter capacitance on the CS pin during each cycle, which helps to minimize the value of the filter capacitor and reduce the current-sensing delay. The UCCx808A-x device is a highly integrated, low-power current mode push-pull PWM controller. The controller employs low starting current and an internal control algorithm that offers accurate output voltage regulation in the presence of line and load variations. The UCCx808A-x family of parts has UVLO thresholds and hysteresis options for off-line and battery-powered systems. The oscillator generates a sawtooth waveform on RC. During the RC rise time, the output stages alternate on time, but both stages are off during the RC fall time. The output stages switch at 1/2 the oscillator frequency, with ensured duty cycle of <50% for both outputs.

Applications

• High-efficiency switch-mode power supplies
• Telecom DC/DC converters
• Point-of-load power modules
• Low-cost push-pull and half-bridge applications

Key features

• Dual output driver stage in push-pull configuration with current-sensing discharge transistors for improved dynamic response
• 130μA typical startup current
• 1mA typical operating current
• Operating frequency up to 1MHz
• Internal soft-start
• On-chip error amplifier with 2MHz gain-bandwidth product
• On-chip VDD clamp
• Output driver stage capable of 500mA peak source current and 1A peak sink current