This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS549D22: About PMBUS

Part Number: TPS549D22

Hi Team:

Can you help to comment on the following questions, thanks!

1:  there is no statement on the PMBUS Pin , such as open drain, if this device is the open-drain type? if the external pull up is need? because there is no any information related to pull up voltage and resistor in the datasheet and design application circuit.

2:  if 1.8V pull up is recommended?  if 1.8V pull up is ok, it shall be better,

  • Hello,

    The PMBUS pins are high impedance pins that will detect the logic thresholds on the the respective PMBus lines. The need for an external pull up will depend on the capabilities of the PMBus controller. For instance, if you were to utilize the TPS549D22 EVM with a USB2GPIO dongle as the controller, the USB2GPIO controller dongle has internal pullups on the dongle itself that may be configured. However, if the PMBus controller uses an open-drain configuration to drive the PMBus communication, then external pullups will be needed. If you have any information on how you and/or your customer plans to control the PMBus communication, I can provide an answer based on the controller device information. In order to determine the appropriate pull up resistance, this will depend on the current sinking capabilities of the PMBus driver and bus capacitance of the PMBus lines on the circuit board.

    Regarding the 1.8V pull up. This is sufficient for the TPS549D22. Attached are the logic low and high thresholds for each of the PMBus pins.

    Regards,

    Alec Biesterfeld