Hardware Description
2019 Microchip Technology Inc.
DS50002905A-page 39
FIGURE 4-3:
PWM Duty Cycle to Voltage Correspondence.
Considering that the minimum specified voltage for the provided fan is 7V, the minimum
drive setting needs to be set at 16 in order to ensure a reliable fan operation and
tachometer reading.
This minimum drive setting and voltage per duty cycle behavior is dependent on the
drawn current and varies from fan to fan.
is provided only for reference on
how this combination of driver and fan behave and to help with understanding the
relationship between the output voltage and the PWM duty cycle.
Note that by setting the PWM duty cycle at 50%, the fan RPM won’t be set at 50%. This
is where the EMC2103-4 RPM-based Fan Speed Control Algorithm solves the
problem, by automatically adjusting the PWM duty cycle to achieve a target RPM.