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LM96063: Disconnect remote diode-connected transistor and only use the internal die temp sensor

Jason Dai
Expert 3720 points
Part Number: LM96063
Other Parts Discussed in Thread: AMC6821,

Hello e2e,

Could user only use the internal die temp sensor and disconnect remote diode-connected transistor as left D+/D- floating?

therefore, user could still use Fan control close loop function.

Sincerely,

Jason

  • 0
    TI__Expert 6820 points

    Hi Jason,

    The control close loop feature on this device is based on a look-up table that relies on the remote temperature.  Therefore you cannot use this feature with the D+/- pins floating. 

    The AMC6821 can be used for local only closed loop control.  The FDRC1:0 bits need to be set to binary "11" and the IN+/- shorted together

    Thanks,

    David

  • 0 in reply to David Vaseliou
    TI__Expert 3720 points

    David,

    Due to the PCB space limitation, customer couldn't useAMC6821. 

    If user short D+/D-, could PWM pin still output PWM pulse to control Fan speed after power on? If yes, what is the PWM's  duty ratio and frequency?

    Or

    User still need to write the command through i2c to enable PWM pulse output?

    Sincerely,

    Jason

  • 0 in reply to Jason Dai
    TI__Expert 6820 points

    Hi Jason,

    The customer may be able to set the PWPGM bit to 1 in register 0x4A and control the PWM frequency and Duty Cycle using register 0x4C and 0x4D with the diode pins shorted.  The only concern would be if shorting the diode cause fault that keeps PWM pin 100%.  I would have to verify this behavior.   

    Would the customer be ok with this solution?  

    Thanks,

    David

  • 0 in reply to David Vaseliou
    Prodigy 50 points

    Hi David,

    If we use LM96063 and let D+/D- pin short, do the PWM output will keep 100% duty after power on? 

    If yes, can we use i2c bus to change the register setting for change the duty rate? 

    If no, how we can let it work at 100% duty after power on without i2c bus command? 

    Thanks you.

     

  • 0 in reply to joe lee
    TI__Expert 6820 points

    Hi Joe,

    Please see my feedback below. 

    joe lee said:
    If we use LM96063 and let D+/D- pin short, do the PWM output will keep 100% duty after power on? 

    If D+/D- pin short the PWM output will be 0% by default.  

    joe lee said:

    If yes, can we use i2c bus to change the register setting for change the duty rate? 

    If no, how we can let it work at 100% duty after power on without i2c bus command? 

    The PWM will not be 100% by default, but you can use registers 0x4C and 0x4D to configure the duty cycle and frequency of the PWM output.

     

    Thanks,

    David

  • 0 in reply to David Vaseliou
    TI__Expert 6820 points

    Hi Jason,

    I have confirmed that you can control the PWM output manually if the D+/D- pins are shorted using registers 0x4C and 0x4D to configure the duty cycle and frequency.

    Thanks,

    David

  • 0 in reply to David Vaseliou
    Prodigy 50 points

    Hi David,

    Do it possible to let controller have default output after power on, even without change the register?  By HW ? Because we need let Fan action even connect to an defect board.   Thanks you.

  • 0 in reply to joe lee
    TI__Expert 6820 points

    Hi Joe,

    There is no way to change the default register values to the device.  One work around may be to float the D+/D- pins.  This will cause a fault which will make PWM high.  Doing this will not allow you to control the PWM until the fault is resolved.  Changing the Rmt T_CRIT setpoint and Rmt High Setpoint to max values should resolve the fault and allow PWM control. 

    Thanks,

    David