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DRV8871: H-Level period and the L-Level period of PWM

cafain
Mastermind 6365 points
Part Number: DRV8871

HI,

Pulse input up to 200kHz is recommended for fPWM of DRV8871-Q1.
(1) has comments, but I can not understand the contents.

Please tell me the H-Level period and the L-Level period of PWM.

Q1.
If fPWM=200kHz and duty=50%, consider H-Level=2.5μs and L-Level=2.5μs.
16% think that H-Level=2.9us, L-Level=2.1us Is there a problem?
Also
Is 84% in H-Level=4.6us, L-Level=0.4us, is there no problem?

Q2.
"Typical devices require at least 400ns.".......
Although it is written in the comment.
Is 400ns the min period of L=level?

Q3.
Is 800ns min during H=level?

best regards
cafainPWM pulse width DRV8871Q1.pdf

  • 0
    TI__Guru** 114905 points
    Hi Cafain,

    The minimum high level pulse is 800ns. The minimum low level pulse is 800ns. The recommended PWM max is 200kHz.



    "Q1.
    If fPWM=200kHz and duty=50%, consider H-Level=2.5μs and L-Level=2.5μs.
    16% think that H-Level=2.9us, L-Level=2.1us Is there a problem?"

    The 16% does not apply. Both the high pulse and low pulse are > 800ns

    Also
    Is 84% in H-Level=4.6us, L-Level=0.4us, is there no problem?"

    Yes, this is a problem. The low pulse is not > 800ns.

    "Q2.
    "Typical devices require at least 400ns.".......
    Although it is written in the comment.
    Is 400ns the min period of L=level?"

    No. The min low level pulse is also 800ns
    Some devices may operate at less than 800ns, but 800ns is needed to ensure operation across devices.


    Q3.
    Is 800ns min during H=level?

    Yes
  • 0 in reply to Rick Duncan
    Mastermind 6365 points

    Hi, Rick-san

    I appreciate the detailed explanation.
    Again, please confirm 2 points.

    1.
    If the minimum pulse width of Low/High-Level is specified to 800ns, what do 16% and 84% indicate?

    2.
    In the same way 400ns is what you indicated.

    best regards
    cafain

  • 0 in reply to cafain
    TI__Guru** 114905 points
    Hi Cafain,

    1.
    If the minimum pulse width of Low/High-Level is specified to 800ns, what do 16% and 84% indicate?

    16% is the minimum PWM duty cycle at 200kHz. 800ns/5us = .16 or 16%
    84% is the maximum PWM duty cycle at 200kHz. 4.2us/5us = .84 or 84%

    2.
    In the same way 400ns is what you indicated.

    Device operation is unpredictable between 0 and 16%, and 84% and 100%. Some devices may operate as lower than 8% and higher than 92% but this cannot be expected.

    The device will operate at 100% duty cycle.