Specifications

Section 43. High-Speed PWM

High-Speed PWM

43.16.6 Constant Off-Time PWM

Constant Off-Time PWM illustrated in Figure 43-53, is a variable-frequency PWM output where

the actual PWM period is less than or equal to the specified period value. The PWM time base

resets externally after the PWM signal duty cycle value is reached and the PWM signal is

deasserted. This is implemented by enabling the On-Time PWM output called Current Reset

PWM and using the complementary PWM output (PWMxL).

The Constant Off-Time PWM can be enabled only when the PWM generator operates in

independent time base. If an external Reset signal is not received, by default, the PWM period

uses the value specified in PHASEx register.

Figure 43-53: Constant Off-Time PWM

43.16.7 Current-Limit PWM

The cycle-by-cycle current-limit, illustrated in Figure 43-54, truncates the asserted PWM signal

when the selected external fault signal is asserted. The PWM output values are specified by the

CLDAT<1:0> bits (IOCONx<3:2>). The override outputs remain in effect until the beginning of

the next PWM cycle. This is sometimes used in PFC circuits where the inductor current controls

the PWM On-Time. This is a constant frequency PWM.

Duty Cycle

Period

Timer

Value

Programmed Period

PWMxH/L

Value

External Timer Reset

Duty Cycle

Actual Period

External Reset

Note: Duty Cycle represents OFF-Time.