App-20
IM DL850E-01EN
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 according to the last
waveforms in the measurement intervals 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 μs.
(1) When the input signal is less than or equal to 25 kHz
The module measures the times of occurrence of the pulse edges (T1, T2, and T3) in measurement intervals
A and B.
In measurement interval C:
For the pulse width: The module calculates the pulse width as T2 − T1.
For the duty cycle: The module calculates the duty cycle as (T2 − T1)/(T3 − T1).
Input pulse
Measurement
interval: 40 μs
Time: T1
Time: T2 Time: T3
Pulse width = T2 – T1
Duty = (T2 – T1)/(T3 – T1)
Pulse width
40 μs
A
B
C
40 μs
(2) When the input signal is greater than or equal to 25 kHz
The DL850E/DL850EV measures the times of occurrence of the last pulse edges (T1, T2, and T3) in
measurement interval A.
In measurement interval B:
For the pulse width: The module calculates the pulse width as T2 − T1.
For the duty cycle: The module calculates the duty cycle as (T2 − T1)/(T3 − T1).
Input pulse
Pulse width = T2 – T1
Duty = (T2 – T1)/(T3 – T1)
Measurement
interval: 40 μs
T1 T2 T3
Pulse
width
40 μs
A
B