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Original question:

THS4551: SPICE models

THS4551: Single ended source to ADS1288

Lkhagvajantsan Damdinsuren
Prodigy 20 points
Part Number: THS4551
Other Parts Discussed in Thread: ADS1288, THS4501, , ADS1285EVM-PDK, ADS1285

Tool/software:

Hello, 

I am designing interface of single-ended source (ADXL354 accelerometer, with output impedance of 32kOhms) to delta sigma ADC model of ADS1288.

Since I do not have details of internal PGA differential amplifier of the ADS1288, may I use THS4551 or THS4501 models, assuming those are similar.

Thank you.

  • 0
    TI__Genius 17576 points

    Hello Lkhagvahantsan,

    I am switching this thread to the ADC team so they can support your questions on modeling the internals of the data converter.

    If you end up needing a fully-differential amplifier I can assist you further. In general, you can use PGA and FDA models to simulate internal ADC blocks as long as you understand the specifications of the internal amplifiers within the ADC.

    As I do not know what type of amplifier is internal to the ADS1288, I will have the precision ADC (PADC) team give their input here first. 

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    TI__Mastermind 42951 points

    Hi Lkhagvajantsan Damdinsuren,

    As Mark mentioned in your other post (https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1457609/ads1288-ads1288?tisearch=e2e-sitesearch&keymatch=%2520user%253A637038#), we do not have a model to share for the ADC input stage.

    You should instead get the ADS1285EVM so you can perform any required testing and better understand the input stage characteristics.

    -Bryan

  • 0 in reply to Alec Saebeler
    Prodigy 20 points

    Hello Alec Saebeler,

    Thank you very much for your reply.

    Yes I need the single-ended to fully differential amplfier stage, your assitantance is appreciated.

    After that let me simulate internal ADC blocks.

    The ADXL354 output has series resistance of 32kOhm, we will use external capcitor 27nF to set cutoff frequency to 200Hz, final ODR output data rate will be 125Hz for low noise seismic signals.

    I insert here screenshot of ADXL335 MEMS acceleromter which is similar to target sensor ADXL354.

     

    Best regards,

    Lhagva   

  • 0 in reply to Lkhagvajantsan Damdinsuren
    TI__Genius 17576 points

    Hello Lkhagva,

    Do you have a range for what the voltage of the output signals would be from ADXL335?

    I can support designing a THS4551 front-end here and get you started before you consider ADC input structure.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 20 points

    Hello Alec,

    Thank you for your reply.

    ADXL354 has unipolar single ended output. The sensor has Output Full-Scale Range (FSR) of +-2g, Sensitivity is 400mV/g, so 2g will produce 800mV.

    The 0 g bias output is nominally equal to V1P8ANA/2, where V1P8ANA is 1.8V and half of it makes 0.9V  

    Therefore output signal minimum will be 0.1V (represents -2g) and maximum will be 1.7V (represents +2g).

    I imagine output of the THS4551 will be centered at 2.5V, gained about 1.8 times, which has approximate range of 1.06V to 3.94V. However I follow your recommendation on output of FDA..  

    Yes, please assist designing front-end circuit, after that we will decide ADC.  

    Best regards,

    Lhagva 

  • 0 in reply to Lkhagvajantsan Damdinsuren
    TI__Genius 17576 points

    Hello Lhagva,

    Great!  Thank you for the explanation for the ADXL354, I knew you could explain it to me better than I could read it on the datasheet.

    I will work on an FDA circuit for you and send it over once I have it simulated and understood to be good.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 20 points

    Hello Alec,

    Thank you for your reply. I have thoroughly reviewed the datasheet.

    Could you please recommend suitable evaluation boards along with your simulation results.

    We plan to purchase ADS1285EVM-PDK Evaluation kit.

    As Mark suggested, we have also reviewed the ADS131X0X ADC and consider it to be the best candidate for our requirements. However, for testing and  evaluation stage we will proceed with ADS1285. 

    Best regards,

    Lhagva