8-bit PIC® MCU Slope Compensation Module

The Slope Compensation (SC) module is designed to provide the necessary slope compensation for fixed frequency, continuous current, and current mode switched power supplies. The SC module in a PIC® microcontroller (MCU) device works by quickly discharging an internal capacitor at the beginning of each Pulse Width Modulation (PWM) period of the switching power supply control signal. An internal current sink charges this capacitor at a programmable rate. As the capacitor charges, the capacitor voltage is subtracted from the current reference voltage, producing a linear voltage decay at the required rate.

SC Circuit Block Diagram

The core of the SC module contains the following:

• On-chip capacitor in series with the voltage source,
• Shorting switch across the capacitor,
• Calibrated current sink, and
• One-shot pulse generator to ensure the switch is closed long enough to completely discharge the capacitor.

Connections

The input to the SC module can be connected to the following signals:

• Comparator C1
• Comparator C2
• Op-amp

The output of the SC module can be connected to the following signals:

• COG1
• COG2
• Comparator C1
• Comparator C2