PIC24FJ128GA010_09 Datasheet, PDF (118/240 Pages) Microchip Technology – 64/80/100-Pin General Purpose, 16-Bit Flash Microcontrollers

PIC24FJ128GA010 FAMILY
EXAMPLE 13-1: PWM PERIOD AND DUTY CYCLE CALCULATIONS⁽¹⁾
1. Find the 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/FOSC = 62.5 ns
PWM Period = 1/PWM Frequency = 1/52.08 kHz = 19.2 μs
PWM Period = (PR2 + 1) • TCY • (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 = log₁₀(FCY/FPWM)/log₁₀2) bits
= (log₁₀(16 MHz/52.08 kHz)/log₁₀2) bits
= 8.3 bits
Note 1: Based on TCY = TOSC * 2, Doze mode and PLL are disabled.
TABLE 13-1: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 4 MIPS (FCY = 4 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 TCY = TOSC * 2, Doze mode and PLL are disabled.
TABLE 13-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 16 MIPS (FCY = 16 MHZ)⁽¹⁾
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 TCY = TOSC * 2; Doze mode and PLL are disabled.
DS39747E-page 118
© 2009 Microchip Technology Inc.