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Original question:

UCC21750QDWEVM-025: Temperature Monitoring using thermistor inside the power module

UCC21750QDWEVM-025: Temperature and DC Link Monitoring using AIN pin

Weichi Zhang
Prodigy 40 points
Part Number: UCC21750QDWEVM-025
Other Parts Discussed in Thread: UCC21750

Hi Team,

Based on the Datasheet of UCC21750, the AIN pin can be used for DC-link voltage and temperature monitoring. From my understanding, the internal current source is used to generate a voltage across the internal/external NTC for temperature measurement (Rt=V/I), whilst the dc-link voltage measurement is more of based on the voltage divider, which is the voltage across R42. Then for temperature monitoring purpose, can I remove R42 in 'UCC217XX Family Driving and Protecting SiC and IGBT Power Modules and Transistors', Fig. 2, Block 4?

If this is not the case, during the dc-link voltage monitoring, rather than measuring the divider R42 from the dc-link voltage (Vdc*[R42/(R42+R33+R34+R35+R36+R37)]), there is also a voltage across R42 from the internal current source, V= I*R = 200e-6x6.19e3 =1.238V. How to determine the dc-link voltage from VAIN then?

Many thanks,

Weichi

  • 0
    TI__Expert 4875 points

    Hello Weichi,

    Thanks for your question. For temperature monitoring, you may remove R38 to disconnect the BUS+ terminal. Additionally, you may remove R42.

    If you are monitoring the dc link voltage, you will keep R38 and remove R40 to disconnect the TR+ terminal. During dc link monitoring, the voltage across R42 is determined by the voltage divider, as you said, including R37, R36, R35, R34, R33 and R42, and the bus voltage at BUS+. The voltage is determined as such, and is not impacted by the current source. 

    Regards,

    Audrey

  • 0 in reply to Audrey Dearien7
    Prodigy 40 points

    Many thanks Audrey. 

    Best regards,

    Weichi