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Original question:

AMC1204: How to read the AMC1204 output signal

AMC1306M25: AMC1306M25 replace AMC1204. Need change anything?

Eggsy Pang
Expert 4985 points
Part Number: AMC1306M25
Other Parts Discussed in Thread: AMC1204,

HI team,

My customer used AMC1204 in old project. They would like to upgrate to AMC1306. Do they need change anything? Including software and hardware.

Thanks!

  • 0
    TI__Guru**** 168605 points

    Hi Eggsy,

    When you look at the datasheets for the AMC1204 and the AMC1306M25, you should notice a couple things on the hardware side:

    1. The AMC1204 comes in two different package options while the AMC1306M25 only has one.  Assuming you are using the DWV package, you can swap in the AMC1306M25 - they are pin-to-pin compatible.
    2. The AMC1204 has a switched capacitor input stage (see Figure 44), while the AMC1306M25 has more of a traditional differential amplifier input stage (see Functional Block Diagram, page 21).  The main influence here is the input impedance - the AMC1205 is ~12.5 kohms while the AMC1306M25 is ~22 kohms.  If you are using the AMC1204 in a current sensing application with a small value shunt resistor, this should not be an issue.

    On the software side of things, you need to consider:

    1. The AMC1204 uses the falling MCLK edge to shift data out of the modulator (see Figure 1) while the AMC1306M25 uses the rising edge of MCLK to shift out data (see Figure 1).  Depending on the setup and hold time needs of the digital filter used in the application, software changes may be required.
    2. The AMC1306M25 has fail-safe features (see section 8.4.1) not found in the AMC1204.  This does not necessarily mean any software changes are necessary, its just something you need to be aware of.
    3. If the AMC1204 is being used in a voltage sensing application, you will most likely have to change the way you account for offset and gain errors because of the difference in the input impedance of the devices (see item #2 above).

    Do let us know if you have any further questions!

  • 0 in reply to Tom Hendrick
    TI__Expert 4985 points

    Hi Tom,

    Thanks for your so great information in detail!

    My customer used AMC1204DWV for current sensing, which testing motor current in line.

    So as for your above suggestion, they don't need to chnage hardware.

    But as for the software, they need changing to read shift out data when rising edge of MCLK, right?

    I saw, "Depending on the setup and hold time needs of the digital filter used in the application, software changes may be required."

    It have "may be". Does it mean we don't need change software if we meet something  requirement 

    If we don't change the software, what happen?

    What is meaning of  "setup and hold time needs of the digital filter"?

    Could you provide it in detail?

     Thanks!

  • 0 in reply to Eggsy Pang
    TI__Guru**** 168605 points

    Hi Eggsy,

    I do not know what you are using as a digital filter. Whatever the controller is, there will be some finite setup and hold time that the FPGA/MCU/DSP will need to see in order to read valid data.  With the AMC1204, data changes on the falling clock edge with a minimum delay of 3nS and maximum delay of 15nS - the implication here is that the digital filter will use the rising clock edge to read a valid (stable) output data bit.  Assuming a 50/50 MCLK at 20MHz, there will be ~10 nS 'setup time' and 25 nS 'hold time'.  With the AMC1306M25, if the digital filter uses the rising clock to validate data, the setup time increases, but the hold time is only ~3.5nS. 

    You will need to do the math on this based on the needs of the controller.  As an example, the C2000 SDFM needs 5nS minimum for both setup and hold times against a rising clock edge.