This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • Resolved

ADS4222: Recommendation of front end circuit for Single ended to Differential signal with isolation

Prodigy 80 points

Replies: 3

Views: 198

SE-TF-Diff-ADS_01_11_2019.TSCPart Number: ADS4222

Hi,

Please suggest the front end circuit to connect ADS4222, 

Currently  designing an custom board in which the single ended pulse signal has to be isolated.

The  Pulse duration is 1us to 6us, which is having amplitude of 0 to +10V with 50 ohm impedance.
and Frequency of the signal 150KHZ to 10MHZ .

so transformer has been chosen to isolate from primary to  secondary 

The question is how to step down the voltage from 0 to +10V  to 0 to 1V ? as ADS4222 supported is Max 2Vp-p

I went through few application notes from TI but am not able to come up with solution.  Which method to use,

1) A transformer having  Primary to secondary with 4:1 ratio  from coilcraft (SWB1010-SML ) then connect to differential amplifier with unity gain (THS4500) to ADS4222

2)A Transformer with 1:1 ratio (WBC1-1TL) and voltage divider circuit at secondary side (attached the TINA file) then connect to differential amplifier with unity gain (THS4500) to ADS4222

3)To Use an Inverting amplifier attenuate the signal  and connect to the primary side of transformer  with 1:1 ratio and then connect to differential amplifier with unity gain (THS4500) to ADS4222 

4)To Use an Inverting amplifier attenuate the signal  and connect to the primary side of transformer  with 1:1 ratio and connect using transformer coupled path as in Evaluation schematic circuit of ADS4222

ADS4222 is connected to FPGA using CMOS outputs.

The clock signal is driven from FPGA LVCMOS 65MHZ  to ADT4-1WT Minicircuits 50ohm single ended  to differential

Attached the TINA circuits. (issue: Differential Output swing is not as per the datasheet, please let me know what to be corrected) 

I Purchased ADS4222EVM and TSW1400EVM , before testing it . it would be better for me to fix the front end circuit and test it. Request to suggest ASAP.

Thank you

  • Guru 65570 points

    Chiranjeev,

    How about using an in-line attenuator or resistor pie network to drop down the voltage before it connects to the transformer? I would also send this post to the amplifier forum to see if they have any suggestions.

    Regards,

    Jim

  • In reply to jim s:

    Jim,

    Thank you for valuable suggestion.

    I have attached the circuit and output for review (circuit with pi network of ideal values considering source 50 ohm and load 50 ohm).  Please let me know for any corrections.

    also i will wait for Amplifier team recommendations.

      TI_Answer.TSC

  • Guru 65570 points

    In reply to chiranjeev N:

    Chiranjeev,

    As long as the INP/M are within the limits of the data sheet, you should be Ok.

    Regards,

    Jim

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.