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TPS65720: Getting temperature from TS pin

user6090715
Prodigy 20 points
Part Number: TPS65720

Hi!

I want to reduce the charge current in a product I am developing when the temperature is below a certain degree. 

From what I can see in the datasheet for the TPS657201 PMIC the TS_OUT pin can be used to read a voltage that corresponds to a temperature. The voltage interval is 0 to 1.4V and the corresponding temperature scale is -20 to 60 degrees Celsius. How is this conversion made? Is it a linear conversion? 

How would one go about to get a battery temperature measurement using the value from the TS_OUT pin?

Thanks in advance!

Best regards,

Björn

  • 0
    TI__Mastermind 30280 points

    Please refer to Section 8.3.10.2 Internal Analog Multiplexer (BAT, TS, TS_OUT); TPS657201, TPS657202 Only on page 28 of the TPS65720 datasheet.

    When TS pin is connected to TS_OUT, <opamp_mux> = 1b, then the voltage range from 0V to 1.4V corresponds to a temperature range from -20C to +60C.

    The voltage to temperature relationship only applies when a 10k NTC, B=3380K resistor is connected from the TS pin to GND.

    This B value signifies B25/50, the nominal rating for NTC resistors which defines the temperature-resistance relationship from 25C to 50C. All NTC resistors have multiple B values, one for each temperature range that was measured. Since the TS_OUT range is supposed to be -20C to +60C, the B25/50 value will not hold across the wider range so the results from -20C to +25C and from +50C to +60C will vary slightly depending on which NTC resistor you use.

    Since the full details of the schematic are not shown in Figure 15, it is difficult to provide the exact answer you are looking for.

    Simply put, the answer is "No, the properties of an NTC are not linear, therefore the output at the TS_OUT pin will not be linear".

    The best way for you to verify the performance would be to used the TPS65720EVM-515 board and measure the TS_OUT pin at the temperatures you are interested in using to increase or decrease the charging current. You will need to remove R2 on the PCB and replace it with a 10k, B=3380K NTC resistor to begin your testing.