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PGA300: No Output on External Temperature Sensor

Ed Payne
Intellectual 375 points
Part Number: PGA300
Other Parts Discussed in Thread: PGA900

Hello:

I am using external temperature sensor in PGA300 and connect PT100 to INT+ (pin 21) and INT- (pin 22), the reading was always 7FFF (2.5V), and I have tried all configurations in GUI and still the same.

I read PGA900 manual, there is 4.99K resistor between INT+ (pin 21 in PGA300) and GND, can I apply this with PGA300?

Please help!

Thank you!

Ed

P.S. What does TSEM_N in EEPROM setting mean? like single-end or differential?

  • 0
    TI__Mastermind 31655 points

    Hello,

    You will need to configure the ITEMP current source to provide a current excitation for your temperature sensor, and you should set TSEM_N so that the PGA300 is operating as a differential amp for the temperature input. 

    You should not place a resistor between INT+ and GND if you plan to use an external temperature sensor.

    I would recommend using a higher resistance RTD like a PT1000 instead of the PT100 just to help increase the accuracy. With a two-wire measurement like what we are doing with the PGA300, you want the RTD's resistance to be much larger than the resistance that the wire traces contribute. This is for noise reduction and to increase accuracy.

    Regards,