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Original question:

AMC6821: Application: FAN speed control abnormal

AMC6821: Application: FAN speed measurement (R.P.M) from 0x08 & 0x09 register

Kay Chen53
Expert 2225 points
Part Number: AMC6821


Hi there:

customer side would like to check the R.P.M reading of AMC6821 register whether match the real case FAN speed. 

But the reading from 0x08 & 0x09 was always 0xff, may we know the how to read the speed correctly?

and from the tool set of EVM,  we know could convert the RPM reading from register, but how is that work? 

( ) 

thanks again. 

  • 0
    TI__Mastermind 43955 points
    Hi Kay,

    Thank you for your question. A TI representative will get back to you tomorrow, as today is a holiday.

    Thanks for your understanding,
    Ren
  • 0 in reply to Ren Schackmann
    TI__Genius 11750 points
    Hi Kay,

    I'm currently looking into your request, and will update you with the information that I find.

    Best Regards,
    Matt
  • 0 in reply to Matthew Sauceda
    TI__Prodigy 240 points
    Hi Kay,

    How have you configured the configuration registers 1 and 2?

    Also, could you send me a schematic of the design?

    -Megan
  • 0 in reply to Megan Anderson
    Expert 2225 points

    Hi Megan:

    To attache the schematic of customer side , for the configuration register 1 & 2 would check with RD again. 

  • 0 in reply to Kay Chen53
    TI__Genius 11750 points
    Hi Kay,

    Thanks for the schematic. We will review and get back to you once we finished acquiring feedback.

    Best Regards,
    Matt
  • 0 in reply to Matthew Sauceda
    Expert 2225 points

    Hi Matt:

    update register configuration information from customer side.

  • 0 in reply to Kay Chen53
    TI__Prodigy 240 points
    Hi Kay,

    Could you share the oscilloscope capture from the TACH pin output of the AMC6821?

    Also, can you share with me your TACH-Low-Limit, TACH-High-Limit, and TACH-SETTING registers?

    Best,
    Megan
  • 0 in reply to Megan Anderson
    Expert 2225 points

    Hi Megan:

    our customer side RD member is under collecting the information;

    BTW, could you help to share example waveform of TACH pin & registers  value for example?

    Perhaps we could also check it at the same time?

  • 0 in reply to Kay Chen53
    TI__Prodigy 240 points
    Kay,

    You will have to give me some time to test this on my bench and provide those waveforms.

    Thanks,
    Megan
  • 0 in reply to Megan Anderson
    TI__Expert 7855 points
    Kay,

    Did the customer make any measurements?

    -Kelvin
  • 0 in reply to Kelvin Le THS
    Expert 2225 points

    Hi Kelvin & Megan:

    Customer side was expecting us to provide some example waveform of TACH pin & registers  value could compare.

    Could we use the bench report from you to provide firstly? 

    Thanks again. 

  • 0 in reply to Kay Chen53
    TI__Prodigy 240 points

    Kay,

    Thank you for your patience while we gathered data. We set configuration register 1 to 0x15 and configuration register 2 to 0x3f (from the information you gave us), and kept the other registers to default. Below shows the register values from the GUI that we used, and I've attached our configuration file (if you are using our GUI).

    Fullscreen register_configuration.txt Download 
    21	49	3 	15	3F	83	8 	0 	0 	20	19	19	3C	0 	46	50	0 	64	50	0 	69	1D	55	55	52	41	61	B3	8 	FF	FF	0 	0 	FF	FF	0 	0

    We were able to read RPM values from the EVM GUI as shown in the image below, as well as provided an example waveform from the TACH pin. 

    I would try changing the registers back to their default values and changing only configuration register 1 & 2 and see if you are able to read from the TACH pin.

    Best,

    Megan

  • 0 in reply to Megan Anderson
    TI__Expert 7855 points
    Kay,

    Is there any update?

    -kelvin