64GA106 datasheet(171/330 Pages) MICROCHIP

171 / 330 page

 2010 Microchip Technology Inc.

DS39905E-page 171

PIC24FJ256GA110 FAMILY

EQUATION 14-2:

CALCULATION FOR MAXIMUM PWM RESOLUTION(1)

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 (FCY = 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

111

Period Register Value

FFFFh

7FFFh

0FFFh

03FFh

007Fh

001Fh

Resolution (bits)

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

111

Period Register Value

FFFFh

7FFFh

0FFFh

03FFh

007Fh

001Fh

Resolution (bits)

Note 1:

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

(

)

Maximum PWM Resolution (bits) =

FCY

FPWM • (Timer Prescale Value)

log10

log10(2)

bits

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.

TCY = 2 * TOSC =

62.5 ns

PWM Period

1/PWM Frequency = 1/52.08 kHz = 19.2

s

PWM Period

(PR2 + 1) • TCY • (Timer2 Prescale Value)

19.2

s

(PR2 + 1) • 62.5 ns • 1

PR2

306

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

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