DAC161P997: How to connect the HART modem

Could you please help check whether the connection is right? Especially the HART connection part.

Rload = 500 ohm.The current across Rload is normal. My HART master communicates with the transmitter.The HART signal  amplitude at 1200 Hz is lower than 400 mV which is sended from AD5700, while the signal amplitude at 2200 Hz is normal,between 400mV and 600 mV. Is there something wrong in my design? 

Joe or Lucas will get an answer to you after this holiday weekend.

Hi,

Your DAC161S997 connections match up with the connections in the EVAL schematic. It is recommended to use the DAC8740H with the DAC161S997, instead of the AD5700.

There is a similar thread to this as well: https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/819256/dac161s997-how-to-connect-the-hart-modem.

Let me doublecheck some of your nets with another engineer and I will get back to you with more information soon.

Thanks,
Lucas

Thank you for your reply. But  it's DAC161P997.

Hi,

My mistake, the pins are similar between the two, so your connections still look correct.

Can you measure the AD5700 pin 14 HART OUT directly before C219? The direct output of the AD5700 should be the correct voltage. If it is not, then the AD5700 may be causing the issue.

Also, try measuring DAC161P997's pin 14 C2 directly and comparing it to the AD5700's output. These should be relatively the same signal. This can help verify the load of the circuit is correct.

Please verify AD5700's pin 15 REF is 2.5 V as well.

Thanks,
Lucas