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TPS543B20: About API Threshold Setting

Tsukui Yusuke
Guru 21930 points
Part Number: TPS543B20

Hi,

Could you tell me about API Threshold Setting?
The following contents are listed in the data sheet.

Please tell me the API threshold corresponding to the resistance value.
121kΩ(1×)=xx mV
187kΩ(2×)=xx mV
8.66kΩ(3×)=xx mV
78.7kΩ(4×)=xx mV

Customer wants to know the meaning of ”1～4×” and detection point of API.

Best Regards,
Yusuke / Japan Disty

  • 0
    TI__Guru**** 191445 points
    Yusuke-san,

    The threshold points are as follows:
    21kΩ(1×)=15 mV
    187kΩ(2×)=25 mV
    8.66kΩ(3×)=35 mV
    78.7kΩ(4×)=45 mV
  • 0 in reply to JohnTucker
    Guru 21930 points

    John-san,

    Thank you for you kind support.
    Let me ask you one more thing.

    For example,In 78.7kΩ=45mV condition,
    API is activated when the output voltage drops 45mV.
    Is this correct in my understanding?

    Also, could you tell me where TPS543B20 is sensing 45mV?

    Best Regards,
    Yusuke / Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 191445 points
    Yusuke-san,

    The TPS543B20 uses differential remote sense to directly monitor the output voltage. There is an internal high pas 25.5 kHz filter. the voltage is sensed after that filter.
  • 0 in reply to JohnTucker
    Guru 21930 points
    John-san,

    Thank you for your response.
    I understood about the API detection point.

    "For example,In 78.7kΩ=45mV condition,
    API is activated when the output voltage drops 45mV."
    Is my understanding correct?

    Best Regards,
    Yusuke / Japan Disty
  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 191445 points
    Yusuki-san,

    I will double check on the detection point.
  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points

    Yusuki-san,

    From the apps engineer on my team:

    "Control voltage is the voltage at output of internal error amplifier. This error amplifier requires to regulate the output voltage to the reference voltage."

  • 0 in reply to JohnTucker
    Guru 21930 points

    John-san,

    Thank you for you support.
    Can you explain to me in a little more detail please?

    I want to know the relation between the built-in amplifier and the setting voltage.
    When 15 mV setting is changed to 45 mV,
    Is the API functioning faster?
    Customers want API setting guidelines.
    And, Could you tell me the relationship between 1 and 2.

    1．"Control voltage is the voltage at output of internal error amplifier. 

    This error amplifier requires to regulate the output voltage to the reference voltage."

    2．”The threshold points are as follows:"
    21kΩ(1×)=15 mV
    187kΩ(2×)=25 mV
    8.66kΩ(3×)=35 mV
    78.7kΩ(4×)=45 mV

    Best Regards,
    Yusuke / Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 191445 points
    Let me see what I can find out.
  • 0 in reply to JohnTucker
    Guru 21930 points

    John-san,

    Thank you for your response.
    Let me know one more thing.
    If API sensitivity is too high (ex,21kΩ(1×)=15 mV ),
    please tell us the risks of concern.

    I look forward to your reply. 

    Best Regards,
    Yusuke / Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 191445 points
    Yusuke-san,

    I am sending your inquiry out now. Hopefully I will have an answer later today.
  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points

    Yusuke-san,

    When API enable, the RSP/RSN has to pass through the high pass filter (2.5pF and 2.5MOhm). When the signal of RSP/RSN is passed the setting threshold, API will be active.

    When the load increases during the load transient, the output voltage decreases. So, 15mV threshold is hitting first before 25mV, 35mV, and 45mV. If API threshold sets at 15mV, API feature will kick-in after RSP/RSN pass through the high pass filter and 15mV amplitude. If API threshold sets at 45mV, API feature will kick-in after RSP/RSN pass through the high pass filter and 45mV amplitude. So, the output voltage will dip more with 45mV API threshold.

    The disadvantage at 15mV threshold is that the API may be activated and an additional pulse can occur just due to the output voltage ripple.

  • 0 in reply to JohnTucker
    Guru 21930 points

    John-san,

    Thank you for your kind support.
    Let me ask you one more thing.
    Data sheet has the following description.
    "The E48 series resistors with tolerance of 1% or less are recommended"

    What are the risks when using API resistors with accuracy less than 1%?
    (ex,2％ resistor)
    Customers want to know what happens when resistor accuracy is bad

    Best Regards,
    Yusuke / Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 191445 points
    Yusuke,

    The function is set by pin strapping at start up. If the tolerance is too loose, the TPS543b20 may misinterpret the setting to be other than you intend.