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BQ25887EVM: BQ25887 EVM TS pin

Babu Vishwanath Hemath Kumar
Prodigy 230 points
Part Number: BQ25887EVM
Other Parts Discussed in Thread: BQ25887

Hi, 

My name is Babu. Regarding sensing the temperature we have TS pin in the EVM module. In datasheet you have mentioned "temperature window". Can you tell me what is Temperature window you mean exactly?

Regarding the connection of 103AT-2 thermistor , we have to connect one end to TS of Junction J5(2) and another end to J5(1) am I right, just for clarification I am asking?

  • 0
    TI__Genius 10355 points

    Hi Babu, 

    Temperature window is the operating temperature range of the device. You can read more about the uses and purpose of this temperature window in section 8.3.7.4 of the BQ25887 datasheet. For the EVM, an example thermistor voltage divider circuit has already been implemented for understanding the charger's behavior at various TS voltages. You can connect a thermistor to both ends of the J5 junction, as you mentioned, though you will need to disconnect JP7. 

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 230 points

    I have seen in the datasheet  but there is no section 8.3.7.4 as mentioned by you. Can you provide me the details?

  • 0 in reply to Babu Vishwanath Hemath Kumar
    TI__Genius 10355 points

    Hi Babu,

    Apologies, I meant section 8.3.4.5 in the data sheet. The section covers charger behavior at various temperature ranges as well as how to calculate the resistor values for the voltage divider circuit at TS based on your thermistor's resistor values.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 230 points

    Thanks for the section, but in that section you have provided two graphs and one equation where I find difficult to find what is VT1 and VT5. Can you tell me the value of VT1 and VT5.

  • +1 in reply to Babu Vishwanath Hemath Kumar
    TI__Genius 10355 points

    Absolutely,

    This link may help to clarify things as well.

    VT1 is the expected voltage at the TS pin at T1 (based of JEITA Guidelines T1 should be about 0C) and VT5 is the expected voltage at TS pin at T5 (this should be 60C). These voltages are expressed as a percentage of REGN since that is the voltage used to bias the TS circuit. VT1 is typically 73.25% (0.7325) and VT5 is typically 34.375% (0.34375). VT1-VT5 can be found in the electrical characteristics section (7.5) of the datasheet.

    Best Regards,

    Juan Ospina