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TMS320F28379D: Resolver Resolution

Hakan B
Expert 1120 points
Part Number: TMS320F28379D
Other Parts Discussed in Thread: ADS1203

Hi guys,

I want to read a resolver with my 28379d DSP. What is the maximum bit resolution that I can achieve? Moreover, what will be the data update rate then? As you know, in order to increase resolution you should increase the sampling duration (like ADC) or do oversampling in general. This means you have to sacrifice output update rate.

I couldn' find any information about it.

Regards,

Hakan

  • 0
    TI__Mastermind 28275 points
    Hi Hakan,

    The F28379D device has an ADC that can operate in 2 modes: 16-bit and 12-bit. In 16-bit mode, you are looking at an ENOB (Effective Number of Bits) of 14.1 bits and for 12-bit mode, an ENOB of 11.1 bits. Maximum sample rate of 1.1MSPS for the 16-bit and 3.5MSPS for the 12-bit. You can find all this information in the device data manual.

    If you need more resolution than this, you can oversample the signal. The basic idea behind oversampling is, you gain 1-bit of resolution for every 4x you oversample the signal. Keep in mind that this is not limitless and you will run into limitations such as the maximum throughput of the ADC etc. There is plenty of material online about oversampling that goes more in-depth.
  • 0 in reply to Frank Ankapong
    Expert 1120 points
    Frank,

    Thank you for the answer. I know how ADC works, I am not asking about ADC. I am asking about resolvers. If you search the keyword 'resolver' in the manual, you can see that it is only used in sigma delta filter module (section 5.10.5). Moreover in this section, you can not see any connection between sigma delta filter module (SDFM) and ADC, even you look at the block diagram of SDFM (page 134 and 135). So I thought that SDFM is another peripheral like ADC that converts special analog signals (like resolvers). But there is not any information about SDFM resolution (or I couldn't see it). If this SDFM is a sub data processing module of ADC, your comment is totally valid. But there must be a sentence or block diagram in the manual that shows the connection between SDFM and ADC (which I couldn't find).

    Here is the latest manual of f28379d.
    www.ti.com/.../tms320f28379d.pdf

    Regards,
    Hakan
  • 0 in reply to Hakan B
    TI__Mastermind 28275 points
    Hakan,

    My apologies. I assumed your inquiry was about the performance of the ADC. Yes, the SDFM is a separate module and not part of the ADC. As far as I'm aware, the SDFM doesn't have an analog front-end and only takes in digital streams.

    I have re-assigned your post to our SDFM expert who will better be able to answer your question about the SDFM.
  • 0 in reply to Hakan B
    TI__Guru 55700 points
    Kadir,

    SDFM is a filter module and as Frank mentioned it take only sigma delta modulated bit streams and these modulated bitstreams come from SD-modulators (which are external to this chip) like AMC1304, ADS1203 etc.

    ENOB / resolution you can achieve depends upon resolver frequency, SD-modulator bit stream rate, OSR filter settings and not just on SDFM. ENOB / resolution vs OSR settings are generally found in SD-modulator datasheet.

    Regards,
    Manoj