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AMC1306E25: + TMS320F28374S : New to Delta - Sigma ADC, please help

MarkoAnte
Intellectual 750 points
Part Number: AMC1306E25
Other Parts Discussed in Thread: TMS320F28374S, AMC1200, AMC1303E2520, AMC1303E2510

Hi, 

I'm starting a new project and I'm switching form Microchip to TI C2000 Delfino class probably to the - TMS320F28374S. I already used AMC1200 isolation op amp for current measurement and I had good results. Now I'm thinking of going with AMC1306E25 & the DSPs SDFM and I have a couple of questions about the use of a delta sigma adc. 

1) I have seen that there is a Manchester coded option for the DOUT. With this I don't have to run a CLK line form the DSP to the ADC - this is a positive. Are there any negatives in using a Manchester option? 

2) The datasheet says 16 bits of resolution at a data rate of 78 kSPS. Is this the recommended speed/resolution of operation? As I understand, if i set the filters in the DSP differently I can get lower resolution but faster sample rate right? 

3) In the data sheet the clock is listed to be between 5 and 20 Mhz. What would be the TYP clk? The DSPs SDFM works to 25 MHz. Is there any reason why would I not run the ADC at 20 MHz (besides power consumption and EMC)?

4) If I use the Manchester coded setting, and want to use multiple ADC,  can I use multiple different clocks or do the clock have to be synchronised (more of a TMS320F28374S question)? 

Best regards, 

Marko Antesic

  • 0
    TI__Guru**** 171025 points
    Hi Marko,

    This may be more of a question for the TMS320F28374S folks, but let me take a first pass at answering your questions. For Q1.) correct - you do not need to run a clock from the DSP, but you do need to run a clock to the AMC1306. For part of Q4 - since one of the typical applications for the AMC1306 might be a multi-phase motor control system or inverter, you would actually want all phases sampled synchronously so having one local clock service three current phases is the better option. For the rest of Q4, you could use the AMC1303 and save yourself an oscillator. For Q2) you are correct again, you can use a lower OSR and get a faster throughput with a lower resolution. This is common in applications where the same data output from one AMC1306 might be used in two different loops - one for control (higher OSR, higher performance, slower response) and one for protection (lower OSR, lower performance but higher speed/faster response). For Q3) the typical clock is 20 MHz, but 10 MHz is also a popular option. EMC/EMI is usually a concern with higher clock speeds, but minimizing trace lengths and employing good termination techniques on the PWB usually mitigate these issues.
  • 0 in reply to Tom Hendrick
    Intellectual 750 points

    Hi Tom, 

    thank you for your fast response. I did not see the AMC1303 devices, they will save me a lot of trouble in PCB routing. I'm building a 3-phase buck converter, so there is no critical need to sample all 3 currents at the same time. 

    Best regards, 

    Marko 

  • 0 in reply to MarkoAnte
    TI__Guru**** 171025 points

    Hi Marko,

    Take a look at the AMC1303E2510 or AMC1303E2520, there are also 50 mV input versions of this device.

  • 0 in reply to Tom Hendrick
    Intellectual 750 points
    I saw them, I will probably use the AMC1303E2520, I looked for the 50 mV version, but could not find any distributors that would have it in stock. The 250mV version will be also good, the converter is a prototype any way & the parts are pin compatible.

    Best regards,
    Marko