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Tibbo Project System (TPS)
© Tibbo Technology Inc.
7.2.9.27
#16, M1S: Three PWMs With OC Outputs
Function:
Three PWMs with open collector outputs
Category:
Output module
Special needs:
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Power requirements:
5V/20mA
Mates with:
Details
This Tibbit is based on the PIC16F1824 microcontroller and takes advantage of the
PWM channels available on this PIC device. The PIC micro has four PWM channels
but one of the channels cannot be used because it shares I/O lines with the I2C
interface. The I2C interface is utilized for communications with the main CPU of the
and also for PIC firmware upgrades.
The frequency and the pulse width (duty cycle) are set independently for each
PWM channel. The frequency is controlled through a divider and a period value. The
divider allows you to select the base frequency applied to the divider. Available
choices are 32MHz, 8MHz, 2MHz, and 500KHz. The output signal of the PWM can
then be programmed to have the period equal to 4~1024 base frequency periods in
4-period steps (i.e. 4, 8, 12,...1020, 1024). This gives you the output range from
8MHz down to 488Hz. The PWM pulse width can be programmed to have the period
equal to 1~1024 base frequency periods in 1-period steps (1, 2, 3,... 1023, 1024).
Each PWM channel uses one Zetex FFMT491 NPN transistor which is rated for 1A
continuous collector current.