Hello ADI people,
I am trying to use AD9361 internal temp sensor with AUX ADC but encounter one interesting thing. The thing is that temp word which reading back from internal temp sensor is not the same when ENSM at different state. Following are testing configurations and result in detail for your reference.
In my case, AD-FMCOMMS3-EBZ has put in the oven for environment temperature control and AD9361 has set to do periodic temperature measurement. Below is registers setting for internal Temp sensor. Soak in 25 degree C for one hour to achieve thermal balance then start to read temp word. The temp word is around 84 ~ 85 in decimal when ENSM is FDD(both TX and RX is enabled but no RF signal to RX and no IQ data to TX) but temp word reduce to about 74 ~ 75 when ENSM changes to ALERT mode( both TX and RX is disabled but not go to WAIT mode).
0x00B = 0x0 /* Set no offset */
0x00C = 0x0 /* Set in periodic measuring mode */
0x00D = 0x1 /* Set reading time to 0s */
0x00F = 0x0
0x01D = 0x1
I know TX/RX chain will be power down when ENSM is at ALERT mode so that AD9361 will be cooler, but I don't think that will lead about 10 degree C temperature drop. And I did't see any section in UG-570 mentions this phenomenon. So I wonder whether any circuit relation between TX/RX chain and internal Temp sensor? Or any further recommendation for internal Temp sensor usage. Thanks for your help in advance.