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MSP430F47167: wrong clock behaviors

Kien
Expert 3530 points
Part Number: MSP430F47167

Hi,

Please advise what should be the cause of bellowing symptom.

All of ICs has JTAG fuse burnt after the first programming.

Some out of thousand ICs didn't perform as expected. So I tried with a simple code toggling a GPIO every 100ms using SW delay (download via BSL).

Good ICs: waveform is as expected.

Bad ICs: actual toggling cycle is every ~700-800ms.

The symptom goes with the bad ICs when I try swapping ICs between two boards.

  • 0
    Guru 243980 points
    Which clock source are you using? How are you initializing it?
  • 0 in reply to Clemens Ladisch
    TI__Guru 56685 points

    Kien,

    As Clemens has suggested, there is not enough information here to properly asses what's going on. Can you describe how you are using the clock system? there seems to be several errata about the clock system for this, especially around the LF Xtal.

  • 0 in reply to Jace H
    TI__Guru 56685 points
    Kien,

    Do you have some additional information as requested above? With no response soon, I'll assume you have resolved your issue and I will close this thread.
  • 0 in reply to Jace H
    TI__Expert 3530 points
    JH,
    Sorry for my late reply.
    This is the configuration code for clock. It is executed after a delay of few seconds after disabling the WDT. This to make sure the VDD gets higher than 2.2V (errata).

    ...
    FLL_CTL0 |= XCAP11PF; // Configure load caps
    FLL_CTL0 |= DCOPLUS;
    SCFI0 = FN_4 | FLLD_4;
    SCFQCTL = (122 - 1);
    ...

    The crystal requires 12.5pF load cap while the on-chip FLL can only supports 10pF maximum. I am asking the customer to try with external load caps.
    Do you have any other suggestion for me?
  • 0 in reply to Kien
    TI__Guru 56685 points
    Kien,

    I believe you have found your issue with the last statement you gave. Having the wrong load capacitance for an Xtal can cause it not to start at all or to have an off frequency oscillation. this will obviously cause issues with clocking depending on your clocking setup. Please see teh following app note for more information about LF Xtals and MSP430s. http://www.ti.com/lit/slaa322
  • 0 in reply to Jace H
    TI__Expert 3530 points
    Hi JH,
    I did some more tests as below:
    1. I used external 10pF cap and 1pF internal cap -> worked
    2. I used external 1 pF (and 2pF later) and 10pF internal cap -> didn't work

    So I want to ask 2 questions:
    Q1: Can I say there is something wrong with the internal caps on that chip?
    Q2: Do you know if we can do the FA to check the internal caps after the JTAG fuses blown?
  • 0 in reply to Kien
    TI__Guru 56685 points
    Hello Kien,

    As outlined in the app note, several factors can go into the interruption of the oscillating of an Xtal. Keep in mind there is not 10pf setting for internal load caps on the device, but 1pf, 5.5pf, 8.5pf ,and 11pf. these values do include the bond and package capacitance for each pin. this makes adding capacitance in addition to higher internal amounts quite difficult. In order to do proper, you need to do a safety test and possibly an ESR test to the crystal along with load cap balancing to ensure proper oscillation. Also, the internal caps are typical values that can vary from device to device and with operating conditions. So without additional tests and layout review, I cannot say there is something wrong with the internal load caps.

    For your second question, there is not much our Quality team can do in regards to FA on a part where the JTAG fuse is blown..

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