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[FAQ] TPS2372: What happens when TPS2372-3 is configured as Class 7?

Part Number: TPS2372
Other Parts Discussed in Thread: TPS23730

A family of our products use the TPS2372-4 configured as Class 7. The TPS2372-4 is currently not available. It turns out that many of the product models do not exceed Class 6 power levels so we would like to use TPS2372-3 (which is available) in those models but maintain the Class 7 configuration. Is it only the pass-FET Rds-on, current limit, and inrush current limit which is different between the TPS2372-4 and theTPS2372-3 such that the situation described above will work? 

  • Hi Shawn,

    You are right. The main difference between TPS2372-3 and TPS2372-4 are the power rating. Compared to TPS2372-4, the TPS2372-3 has (comparisons based on typical values):

    1. lower power rating (51 W to 71 W)

    2. higher pass FET on-resistance (0.3 Ω to 0.1 Ω)

    3. higher thermal resistance (junction-case 40.2 to 38.0 °C/W)

    4. lower inrush current limitation (200 mA to 335 mA)

    5. lower operation current limitation (1.85 A to 2.2 A)

    6. lower recommended current (1.2 A to 1.85 A)

    The Class 7 is between 51 W to 62 W. When the input voltage of PD is the lowest 37 V, the highest current flow through through PD will be up to 1.68 A and it won't cause current limitation at typical condition. 

    So if your product won't exceed Class 6 in most of time and only reach Class 7 very rarely and within a short time, it looks ok for me to use TPS2372-3. While the best solution is to find enough TPS2372-4. I will check when TPS2372-4 will be restocked and let you know.

    Best regards,

    Diang 

  • Hi Diang,

    Thankyou for the fast reply. So, to be clear, the TPS2372-4 and TPS2372-3 will both negotiate as Class 7 when configured as such, correct?

  • Hi Shawn,

    Yes, both TPS2372-3 and TPS2372-4 should be configured as Class 7 resistor in your case. The negotiation is mainly the PSE send the voltage pulse and read the return current from the PD.

    I currently do not have TPS2372-3, while I tested a TPS23730 which is also rated as Class 6. It can be configured with Class 8 resistor and pass the negotiation:

    Best regards,

    Diang

  • Thankyou Diang.