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PIC24F16KA102 FAMILY

EXAMPLE 15-1: PWM PERIOD AND DUTY CYCLE CALCULATIONS

(1)

TABLE 15-1: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 4 MIPS (FCY = 4 MHz)

(1)

TABLE 15-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 16 MIPS (F

CY = 16 MHz)

(1)

PWM Frequency 7.6 Hz 61 Hz 122 Hz 977 Hz 3.9 kHz 31.3 kHz 125 kHz

Timer Prescaler Ratio 8111111

Period Register Value FFFFh FFFFh 7FFFh 0FFFh 03FFh 007Fh 001Fh

Resolution (bits) 16 16 15 12 10 7 5

Note 1: Based on FCY = FOSC/2, Doze mode and PLL are disabled.

PWM Frequency 30.5 Hz 244 Hz 488 Hz 3.9 kHz 15.6 kHz 125 kHz 500 kHz

Timer Prescaler Ratio 8111111

Period Register Value FFFFh FFFFh 7FFFh 0FFFh 03FFh 007Fh 001Fh

Resolution (bits) 16 16 15 12 10 7 5

Note 1: Based on FCY = FOSC/2, Doze mode and PLL are disabled.

1. Find the Timer Period register value for a desired PWM frequency of 52.08 kHz, where FOSC = 8 MHz with PLL

(32 MHz device clock rate) and a Timer2 prescaler setting of 1:1.

CY = 2 * TOSC = 62.5 ns

PWM Period = 1/PWM Frequency = 1/52.08 kHz = 19.2 μs

PWM Period = (PR2 + 1) • T

CY • (Timer 2 Prescale Value)

19.2 μs = (PR2 + 1) • 62.5 ns • 1

PR2 = 306

2. Find the maximum resolution of the duty cycle that can be used with a 52.08 kHz frequency and a 32 MHz

device clock rate:

PWM Resolution = log

(FCY/FPWM)/log

2) bits

= (log

(16 MHz/52.08 kHz)/log

2) bits

= 8.3 bits

Note 1: Based on T

CY = 2 * TOSC, Doze mode and PLL are disabled.

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