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Purpose of series resistor in 28377D experimental kit.

Amtech
Genius 4535 points
Other Parts Discussed in Thread: TMS320F28377D, TMDSCNCD28379D

Hi All,

I am using 28377D experimental kit for my testing purpose. I am going to develop new control card based on TMS320F28377D and following thing confuse me.

  1. On experimental kit there is 39Ω(R10) series resistor with TDO pin. But in data sheet(Pg. No: 66) that pin is directly connected to JTAG TDO pin(without any series resistor). So, which is better?

  2. VREGENZ pin tied to 3.3VDD through series resistor of 0Ω. Why you provide that resistor is there any specific reason or future need?

  3. All VDDIO is directly connected to 3.3VDD. But, pin no. F4 and G4 is connected through 0Ω series resistor. Why? Is it for any specific reason or future need?

Regards,

Maulik Timbadiya

  • 0
    TI__Guru 57255 points

    Hi Maulik,

    You've done a good job analyzing the schematics.  What you have mentioned are all pretty solid questions and I can understand why you might ask each based on the documentation.

    1. Please refer to Note (3) in the pin descriptions table of the device datasheet.  The resistor is meant to reduce potential ringing on the output - not knowing how the design would be used, we decided to be safe on the controlCARD design.  TDO is one of several pins that may need a series resistor.

    2. We wanted to have this option for internal TI experimentation/debug use.  No need for this in a customer design.

    3. We wanted to have this option for internal TI experimentation/debug use.  No need for this in a customer design.


    (I notice that you are referring to the F28377D schematics - please note that there is a new version of the controlCARD R1.3 - which will be sold with '379D silicon as the TMDXCNCD28379D/TMDSCNCD28379D.  It has a few upgrades over the R1.1A design)


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Genius 4535 points

    Dear Brett,

    First of all thank you very much for your appreciation.
    But, Can you help to solve my below mentioned query?

    Name : "Diode protection on ADC pin for 28377D experimental kit"
    e2e.ti.com/.../488768

    Also help to resolve this:

    https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/489159

    Regards,
    Maulik Timbadiya