The UCC3808A is a family of BiCMOS push-pull, high-speed, low-power, pulse-width modulators. The UCC3808A contains 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 UCC3808A 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 60 ns to 200 ns depending on the values of the timing capacitor and resistors, thus limiting each output stage duty cycle to less than 50%.
The UCC3808A 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 off-line and battery powered systems. Thresholds are shown in the table below.
The UCC3808A is 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.
Dual Output Drive Stages in Push-Pull Configuration
Current Sense Discharge Transistor to Improve Dynamic Response
130-µA Typical Starting Current
1-mA Typical Run Current
Operation to 1 MHz
Internal Soft Start
On-Chip Error Amplifier With 2-MHz Gain Bandwidth Product
On Chip VDD Clamping
Output Drive Stages Capable of 500-mA Peak-Source Current, 1-A Peak-Sink Current