MCP39F511 datasheet(44/62 Pages) MICROCHIP

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MCP39F511

DS20005393B-page 44

 2015 Microchip Technology Inc.

8.2

PWM Period

The PWM period is specified by writing the PWM

Period bits of the PWM Period register. The PWM

period can be calculated using the following formula:

Equation 8-1:

The PWM Period is defined as 1/[PWM Frequency].

When PTIMER is equal to PWM Period, the following

two events occur on the next increment cycle:

• the PWM timer is cleared

• the PWM pin is set. Exception: If the PWM Duty

Cycle equals 0%, the PWM pin will not be set.

8.3

PWM Duty Cycle

The PWM duty cycle is specified by writing to the PWM

Duty-Cycle register. Up to 10-bit resolution is available.

The PWM Duty-Cycle register contains the eight MSbs

and the two LSbs. The following equations are used to

calculate the PWM duty cycle as a percentage or as

time:

EQUATION 8-1:

PWM Duty Cycle can be written to at any time, but the

duty-cycle value is not latched until after a period is

complete.

The PWM registers and a two-bit internal latch are

used to double-buffer the PWM duty cycle. This

double-buffering is essential for glitch-less PWM

operation.

The maximum PWM resolution (bits) for a given PWM

frequency is shown in Equation 8-2.

EQUATION 8-2:

MAXIMUM PWM

RESOLUTION BASED ON

A FUNCTION OF PWM

FREQUENCY

PWM Period = [(PWM_Frequency) + 1] × 2 × PTIMER × (Prescale Value)

PWM Duty Cycle (%) = (PWM_DUTY CYCLE>)/(4 × PWM_FREQUENCY)

PWM Duty Cycle (time in s) = (PWM_DUTY_CYCLE) × PWM_TIMER_PERIOD/2 × (Prescale Value)

Note:

If the PWM duty cycle value is longer than

the PWM period, the PWM pin will not be

cleared.

TIME R



PWM

--------------------------





log



log

----------------------------------------bits

PWM Resolution (max)

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