Vault 7: Projects

This publication series is about specific projects related to the Vault 7 main publication.

2010-2013 Microchip Technology Inc. DS39881E-page 137
PIC24FJ64GA004 FAMILY
EXAMPLE 14-1: PWM PERIOD AND DUTY CYCLE CALCULATIONS
(1)
TABLE 14-1: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 4 MIPS (FCY = 4 MHz)
(1)
TABLE 14-2: 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 8 1 1 1 1 1 1
Period Register Value FFFFh FFFFh 7FFFh 0FFFh 03FFh 007Fh 001Fh
Resolution (bits) 16 16 15 12 10 7 5
Note 1: Based on F
CY = 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 8 1 1 1 1 1 1
Period Register Value FFFFh FFFFh 7FFFh 0FFFh 03FFh 007Fh 001Fh
Resolution (bits) 16 16 15 12 10 7 5
Note 1: Based on F
CY = 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.
TCY = 2 • TOSC = 62.5 ns
PWM Period = 1/PWM Frequency = 1/52.08 kHz = 19.2 s
PWM Period = (PR2 + 1) • T
CY • (Timer2 Prescale Value)
19.2 s = (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
10
(FCY/FPWM)/log
10
2) bits
= (log
10
(16 MHz/52.08 kHz)/log
10
2) bits
= 8.3 bits
Note 1: Based on T
CY = 2 * TOSC; Doze mode and PLL are disabled.

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