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Original question:

CC3220MOD: CC3220MOD Schematic and Gerber for review

CC3220MOD: Power on reset

Ed Richter
Prodigy 60 points
Part Number: CC3220MOD
Other Parts Discussed in Thread: , TPS3839

I was looking at support thread: "CC3220MOD: CC3220MOD Schematic and Gerber for review" and "CC3220MODA: CC3220MODA questions" and I have a follow-up question. I can't get my program to execute properly on power up on the CC3220MODASF LaunchPad when I configure it like the circuit in this support thread. I removed the J3, J5 and J6 jumpers (disconnecting the XDS microcontroller from the CC3220MOD). I shorted J10 to connect VBAT_RESET to 3.3V. I removed J16 to remove the shottky diode and another 100k pullup connected to the nReset pin (and all other power to the BRD circuitry). However, when I power up the LaunchPad, my flashed program never starts executing. However, if I hit the reset button (SW1), it always works.

I think I need to add a reset IC like the TPS3839L30DQNR to my CC3220MOD design to get my code to execute on power up correctly. Does that sound right?

Thanks

  • 0
    TI__Mastermind 46531 points

    Hi Ed,

    You said you configured your LaunchPad like the circuit in one of those threads. Can you please share the circuit here?

    See Section 5.14.1 Power-Up Sequencing in the datasheet. Note that for the CC3220MOD to boot properly, nRESET must go high roughly 3ms after VBAT is high (T1). 

    Try measuring the VBAT and nRESET signals when you first power up your LaunchPad with an oscilloscope and share the scope shots. 

    BR,

    Seong

  • 0 in reply to Seong Kim
    Prodigy 60 points

    Hi Seong – thanks for responding. I don't have my custom board yet. I just moved the jumpers (as described in my post) on the LaunchPad (see attached pic) so that there were no external connections to the nReset pin - like in your schematic on the other post. The datasheet says you should tie the VBAT_RESET to VBAT if you aren't always driving nReset. I thought that implied that it was ok to never drive nReset as long as you connected VBAT_RESET to VBAT.

     I didn’t capture the scope traces but I looked at them and the nReset definitely did not meet the 5ms requirement after VBAT stable nor did the LaunchPad execute the code correctly on power up. That is what prompted my question:

    "I think I need to add a reset IC like the TPS3839L30DQNR to my CC3220MOD design to get my code to execute on power up correctly. Does that sound right?"

    Thanks

  • 0 in reply to Ed Richter
    TI__Mastermind 46531 points

    Ed,

    I just tried testing this on my own LaunchPad with the same jumper configuration and the module is able to run the application image without requiring a reset. There may be an issue with your particular board. 

    You can add a reset IC to your custom board if you'd like but is normally not a requirement. 

    If you bought your LaunchPad thorugh the TI store, you can reach out to the support for the store and request an exchange. If you ordered it from another vendor, you might be able to do the same with them, but we don't control that.

    BR,

    Seong

  • 0 in reply to Seong Kim
    TI__Mastermind 46531 points

    Hey Ed,

    For the CC3220MOD to power up and function properly, the nRESET must go high roughly 3ms after VCC3V3 goes high (see Section 5.14 in the datasheet). The TPS3839 is concerning because the datasheet states that the reset output remains low for 200ms after VDD voltage rises above the threshold voltage.

    BR,

    Seong

  • 0 in reply to Seong Kim
    Prodigy 60 points

    Hi Seong,

    Thanks. I'm finding the documentation a little confusing. In section 5.14, Table 5.2 shows a typical 3ms reset low time - with no max specified. Table 5.12 shows a 5ms min requirement. Are you saying there is a maximum time for nReset low?

    Thanks,

    Ed

  • 0 in reply to Ed Richter
    TI__Mastermind 46531 points

    Hey Ed,

    T1 is the time from when VBAT goes high to when nRESET goes high (see Figure 5-6). And according to the datasheet, 3ms is what you want to shoot for in order for the device to boot up properly.

    However, the CC3220MOD actually has a 100k-Ohm and a 0.1-uF RC tied to the reset pin internal to the module, making T1 10ms. So you do not want to go beyond 10ms or else the device will not power up properly. And adding that reset IC which has a 200ms hold time will not work with the CC3220MOD's reset.

    Table 5-12 lists the JTAG timing parameters, so I'm not sure exactly which table you were referring to. 

    BR,

    Seong