Fawad Munawar said:I am using 8 of AFE5809 chips to get more channel options .My main concern is In the TGC section producing VCNTL signals.(VCNTL_IN_P/VCNTL_IN_N)
This signal is an analog signal that controls the attenuator in the RX AFEs. In the most typical case it provides a ramp voltage to the RX AFE. what voltage range VCNTL signal should be used ?
I am not familiar with the AFE5809, but from looking at the datasheet and the schematics that your provided, I do think that the DAC output range should be from 0V to +1.5V. I think that you can use a single ended input to VCNTLP by grounding VCNTLM. As opposed to a differential input.
For more details on this specification please refer to the Medical Forum, they take care of this AFE5809 part.
Fawad Munawar said:Can I use 0V to +1.5V or it should be always be 10v and -10 v that is mentioned in datasheet .
I assume you are referring to figure 26 in the DAC7811 datasheet.
The DAC can actually use a ±15V reference voltage and anywhere in between, so you can supply a voltage anywhere from -15V to +15V. In this design the limiting factor is the OPA277 amplifier rails.
The DAC7811 is perfectly capable of supplying an output voltage from 0V to +1.5V, you will need a -1.5V reference
Fawad Munawar said:See attached design for your review.
I am unsure as to what the purpose of U114 is. Typically we add a trans-impedance stage to convert the current output of the DAC to voltage. As you can see in figure 26.
1-Can I use precision 1.5v regulator only to this job to generate the VCNTLP signal because I need only +1.5 v and 0.
2-if not possible above option above can I use the following modified version of design below in which I have crossed the parts which I do not need and by changing resistor values I will get +1.5v only ?let me know if this approach works for me .See snapshot below
