AD7328 range select and temperature reading

Hi Vignani,

     We are looking into this. Meanwhile, can I ask what are the values that you reading on the temperature indicator? Please take note that temperature indicator provides local temperature on the ad7328 and should be in pseudo differential. Please refer to the temperature indicator section of the datasheet. We'll get back to you  other questions.

Regards,

Jonathan

The AD7328 is in pseudo-diff mode, +-10V range for all channels. Channel 7 has no connections besides a 470kOhm resistor to analog ground. SPI speed is 2MHz for temperature reading, otherwise 20MHz.

The temperature values I read from channel 7 are in the range 4315..4330 for an (estimated) range of 25-50 degrees on the PCB. If you look at Figure 47 on the data sheet, these values are out of scale, but not by much; there is an offset of about 50, and this could be due to the external 3V reference used.

I will now try with the +-2.5V range and see what happens.

A.Vignani

Da: jcolao

Inviato: mercoledì 6 aprile 2016 17:29

A: VIGNANI Alberto (CRF)

Oggetto: Re:  - AD7328 range select and temperature reading

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AD7328 range select and temperature reading

reply from jcolao<jcolao> in Precision ADCs - View the full discussion<https://ez.analog.com/message/249699?et=watches.email.thread#comment-249699>

Hi Vignani,

     As you mentioned that you using a 3V reference. The reference will be a factor on the input voltage range and also affect the lsb size and can change the output coding of the conversion result. Please also take note that the supply voltage range must also be equal to or greater than the input voltage range.

     Figures 47 are based from using an internal reference 2.5V and range of +/-2.5V. Using a 3V range will have a different conversion result.

Regards,

Jonathan