App-25
IM 701240-01E
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App
App
Index
Appendix
Pulse Width and Duty Cycle Measurement
• When the input signal is less than or equal to 25 kHz, measurement is made as
described in (1).
• When the input signal is greater than or equal to 25 kHz, measurement is made from
the last waveform in the measurement interval as described in (2).
• The sequence of processing described below is performed simultaneously through
pipeline processing. Thus, the period (t) and frequency (f) are updated every 40
µ
s.
(1)When the input signal is less than or equal to 25 kHz
Measures the times of occurrences of pulse edges (T1, T2, and T3) in measurement
intervals A and B.
In measurement interval C:
For pulse width:
Calculates pulse width = T2 – T1.
For duty cycle:
Calculates duty cycle = (T2 – T1)/(T3 – T1).
Input pulse
Time: T1
Time: T2 Time: T3
Pulse width = T2 – T1
Duty cycle = (T2 – T1)/(T3 – T1)
Pulse width
Measurement
interval: 40
µ
s
A
B
40
µ
s
C
40
µ
s
(2)When the input signal is greater than or equal to 25 kHz
Measures the times of occurrences of pulse edges (T1, T2, and T3) in measurement
interval A.
In measurement interval B:
For pulse width:
Calculates pulse width = T2 – T1.
For duty cycle:
Calculates duty cycle = (T2 – T1)/(T3 – T1).
Input pulse
Pulse width = T2 – T1
Duty cycle = (T2 – T1)/(T3 – T1)
T1 T2 T3
Pulse width
Measurement
interval: 40
µ
s
A
B
40
µ
s
Appendix 11 Measurement Principles (Measurement Method and Update Rate) of the Frequency Module