• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 253 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

ADS8887: recommend materials

Jimmy Huang
Expert 2975 points
Part Number: ADS8887
Other Parts Discussed in Thread: THS4551,

Hello:

We have an application in our new project. Please recommend the TI materials. The main functions are as follows:

One sensor, output voltage ± 5V / frequency 10 ~ 2KHz; We want to scale the range signal by 1 / 2 ( We currently selects THS4551). After THS4551 outputs the differential signal, we use a differential ADC to sample ( We currently selects ADS8887) and transmit it to our MCU through ADS8887 SPI interface. Because MCU resources are limited, we hope ADS8887 can borrow 10K sampling rate but output 4KB data. Can this scheme be realized?If not, please recommand better TI materials to replace THS4551 and ADS8887,Thank you.

  • 0
    TI__Mastermind 23050 points

    Hi Jimmy,

    Glad to see you designing with TI parts. THS4551 is a good choice for the input amplifier to many of our high precision devices. Can you elaborate a bit on your system requirements to help me understand what you need? I see your sensor's full scale range is +/-5V and you plan to attenuate this by 0.5. What is the minimum signal from the sensor you need to be able to resolve?

    Can you also clarify what you mean when you say you want the device to borrow 10k sample rate but output 4KB data? Do you mean you need to store the data in memory and you only have 4KB? If this is the case then the converter is going to produce 18bit * 10k = 180k samples/second. That means with 4kB you could store up to 4k * 8 / 180k = 177ms worth of data at a time assuming full memory utilization. Depending on how your memory is allocated though you may not be able to utilize the full 4kB. 

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Expert 2975 points

    Hi Zak：

    I am sorry，there are some problems with the previous description，The requirements are as follows：

    1. The output voltage of the vibration sensor is AC signal with ± 5V and less than 2KHz frequency. After half scaling with THS4551, it is ± 2.5V. THS4551 is powered by single power supply + 5V,that is, the output differential signal of THS4551 is an AC signal swinging on the + 2.5V bias voltage, and then sent to the differential ADC chip at the back end for sampling. The required accuracy is 2mV;

    Is the function description of THS4551 correct?

    2. The ADC chip sends data to our MCU through SPI interface. Our MCU only has 32KB RAM space, so the ADC sampling rate is required to be about 4KSPS. For ADC chip，the sampling rate can be higher, but the amount of output data can be reduced,

    Please help recommend ADC chip，Is ADS8887 suitable？Thank you.

  • 0 in reply to Jimmy Huang
    TI__Mastermind 23050 points

    Hi Jimmy,

    Yes your understanding of the THS4551 is correct. There is also a spice and TINA model for this device that you can use to simulate your circuit. 

    If you only need 2mV of accuracy on a 5V full scale signal (+/-2.5V), then you only need 2500 counts to resolve your signal and you could probably get by with a 12-bit converter. If your MCU has an integrated ADC you could likely just use that directly and would not need an FDA or ADC.

    Best,

    Zak