The UCC28C4x-Q1 series of control integrated circuits provide the features necessary to implement AC-DC or DC?to-DC fixed-frequency current-mode control schemes with a minimum number of external components. Protection circuitry includes undervoltage lockout (UVLO) and current limiting. Internally implemented circuits include a start-up current of less than 100 μA, a precision reference trimmed for accuracy at the error amplifier input, logic to ensure latched operation, a pulse-width modulation (PWM) comparator that also provides current-limit control, and an output stage designed to source or sink high-peak current. The output stage, suitable for driving N-channel MOSFETs, is low when it is in the OFF state. The oscillator contains a trimmed discharge current that enables accurate programming of the maximum duty cycle and dead time limit, making this device suitable for high-speed applications.

Major differences between members of this series are the UVLO thresholds, acceptable ambient temperature range, and maximum duty cycle. Typical UVLO thresholds of 14.5 V (ON) and 9 V (OFF) on the UCC28C42-Q1 and UCC28C44-Q1 devices make them ideally suited to off-line AC-DC applications. The corresponding typical thresholds for the UCC28C43-Q1 and UCC28C45-Q1 devices are 8.4 V (ON) and 7.6 V (OFF), making them ideal for use with regulated input voltages used in DC-DC applications. The UCC28C40-Q1 and UCC28C41-Q1 feature a start-up threshold of 7 V and a turnoff threshold of 6.6 V (OFF), which makes them suitable for battery-powered applications. The UCC28C40-Q1, UCC28C42-Q1, and UCC28C43-Q1 devices operate to duty cycles approaching 100%. The UCC28C41-Q1, UCC28C44-Q1, and UCC28C45-Q1 obtain a duty cycle from 0% to 50% by the addition of an internal toggle flip-flop, which blanks the output off every other clock cycle. The UCC28C4x-Q1 series is specified for operation ambient temperature from –40°C to 125°C.

The UCC28C4x-Q1 series are an enhanced replacement with pin-to-pin compatibility to the bipolar UC284x, UC384x, UC284xA, and UC384xA families. The new series offers improved performance when compared to older bipolar devices and other competitive BiCMOS devices with similar functionality. These improvements generally consist of tighter specification limits that are a subset of the older product ratings, maintaining drop-in capability. In new designs, these improvements can reduce the component count or enhance circuit performance when compared to the previously available devices.