19.4.2.3 Hysteretic Mode

Hysteretic mode control is sometimes called “Bang-Bang” control, where a signal within a power converter is controlled within an upper cutoff and a lower cutoff limit. The Hysteretic mode is used in power supply applications utilizing hysteretic control, such as LED drivers. The Hysteretic mode is enabled by the HME bit (SLPxCON[27]) and requires the SLOPEN bit to be cleared. Hysteretic Control mode enables a single DAC and comparator to monitor both the high and low limits for a signal. DACDAT provides the higher value, while DACLOW provides the lower value. When the DAC changes direction, it uses Transition mode to respond and reach the new value as fast as possible. In Hysteretic mode, the comparator effectively functions as a window comparator. The DAC output races ahead of the monitored voltage in the application circuit. While the DAC is transitioning to the new value, the comparator output is “blanked” via the TMCB[9:0] bits (DACxCON[23:16]) to prevent spurious responses. The state of the PWM output is monitored via the input multiplexer controlled by the HCFSEL[3:0] bits of the SLPxCON register. This module monitors the actual state of the PWM output rather than make assumptions that could damage the application circuit. A configuration example to use Hysteretic mode is shown in Figure 19-4.