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TIDA-01226: Confusion about the reference schematic

Part Number: TIDA-01226
Other Parts Discussed in Thread: DLPC3439, DLPA3005

Hi

In the reference schematic, "MCU_SW_ONOFF",

What is the purpose of designing this signal?

In my design, the power of this signal is changed from P3P3V to MSP_V3P3V,

which brings the boot timing problem.

Best Wishes!

JingMingJun

  • Hello JinMingJun,

    I believe this signal is used to turn on or turn off the MSP430. Let us double check.

    When you said you changed the power from P3P3V to MSP_V3P3V do you mean you changed what the pull-up resistor is being pulled-up to or did you change the buffer voltage? In either case could you elaborate on the reason for the change?

    Thanks,
    Kyle
  • Hello Kyle

    Thank you for your reply.

    From the TI code of the MSP430,
    The falling edge of “MCU_SW_ONOFF” turns off the MSP430, and the rising edge turns on the MSP430. When low, the MSP430 will remain in the same state. When high, the MSP430 will be able to operate according to the state of the “SW_SYS_ON-OFF” signal.
    But I don't know, what is the purpose of this design?

    In the TI schematic,
    The "MCU_SW_ONOFF" signal uses the design of the inverter buff/driver with open-drain out+ pull-up resistor, and the power supply uses P3P3V.
    The power input is DC19V.
    The power supply for the MSP430 is generated by the P5V.
    In my design,
    The "MCU_SW_ONOFF" signal uses the inverting schmitt trigger instead of the inverter buff with open-drain (the pull-up resistor is not required), and the power supply is also the P3P3V.
    The power input is DC15V.
    MSP430 power supply, power supply DC15V → separate generation 5V → 3.3V.

    In the power review experiment, I found that when the power supply was reduced for a short time (and then recovered), the MSP430 and DLPC3439 were turned off (expected), but due to the jitter of the P3P3V, a rising edge occurred in the "MCU_SW_ONOFF" signal, which caused the MSP430 to restart. .
    Therefore, as a countermeasure, I changed the power of the inverting schmitt trigger of the "MCU_SW_ONOFF" signal to the 3.3V power supply for the MSP430.
    Then it caused the MSP430 to boot too fast, so that the power of the DLPC3439 is not ready. . .

    Thanks,
    JingMingJun
  • Hi JingMingJun,

    The MCU_SW_ONOFF is only being used for the cypress part to be able control Proj_On when downloading the firmware via the GUI.
    This signal should than drive the MSP_PROJ_ON signal to the DLP chipset accordingly High/ Low.
    What is the state of the MSP_PROJ_ON signal when you are running is power glitch experiment ?

    what you meant with it is booting up too fast since the MCU_SW_ONOFF is only controlling the MSP_PROJ_ON signal, as far as we know (as this EVM's MSP430 code is written by third party, i can confirm with them).

    what you have connected to the MCU_SW_ONOFF pin on your schematic. Are you using a cypress part ?

    In general, you should also ensure in your design that the power is stable long enough to complete the power-down and power-up

    Thanks,
    Navneet
  • Hi Navneet

    >The MCU_SW_ONOFF is only being used for the cypress part to be able control Proj_On when downloading the firmware via the GUI.

    >This signal should than drive the MSP_PROJ_ON signal to the DLP chipset accordingly High/ Low.

    When MCU_SW_ONOFF goes low, MSP_PROJ_ON is pulled low and held, then the firmware is downloaded. After the firmware is downloaded, MCU_SW_ONOFF goes high, and MSP_PROJ_ON is pulled back to the high level to restore the power-on state. Is that correct?

    >What is the state of the MSP_PROJ_ON signal when you are running is(in?) power glitch experiment ?

    The MSP_PROJ_ON signal will go low and then go back high.

    At the same time, the MSP430 has a stable power supply because of its independent power supply.

    >what you meant with it is booting up too fast since the MCU_SW_ONOFF is only controlling the MSP_PROJ_ON signal,

    >as far as we know (as this EVM's MSP430 code is written by third party, i can confirm with them).

    When the system is powered on, the MSP430 pulls the MSP_PROJ_ON signal high and then monitors the HOST_IRQ signal. If HOST_IRQ is low, the MSP430 considers the DLPC3439 booting up and then initializes it via I2C.

    In fact, in my design, HOST_IRQ is low, not because the DLPC3439 boot is completed, but because the power of the DLPC3439 is not ready.In the TI schematic, MCU_SW_ONOFF(MSP_PROJ_ON) will remain low until P3P3V is ready.

    >Are you using a cypress part ?

    Yes.Please refer to the schematic uploaded.

    Thanks,

    JingMingJun

    CHP_RJBC1047_TIComfirm_190426.pdf

  • Hi JingMingJun,

    I compared the voltages P3P3V and MSP_V3P3V. There is a approx 250us difference in these signals to go high. It may create the problem in MCU to generate the Proj_on.

    Please grab some voltage captures and share it with us :
    1. Sys_pwr to proj_on
    2. MSP_V3P3V to MCU_SW_ONOFF
    3. P3P3V to MCU_SW_ONOFF

    And can you please elaborate your query one more time... i am little confused with what your actual query is. Is it booting problem of DLPC3439?

    DLPC3439 boots up based on the power comes from DLPA and DLPA generates power based on proj_on signal. Proj_on comes from MSP430 based on SW_SYS_ON-OFF state.
    DLPA power sequence you can see in DLPA3005 datasheet www.ti.com/.../dlpa3005.pdf

    I noticed you mentioned you are using 15V DC.. Is there any reason not to using 19V DC ?

    Thanks,
    Navneet
  • Hi JingMingJun,

    Could you please respond to my earlier post... I am waiting for your response.

    If you already resolved this issue, please click on Resolved issue.

    Thanks,
    Navneet
  • Hi Navneet

    I am very sorry to reply so late.

    In my design (refer to the schematic of the upload, different from the TI design),
    when the system is powered on, MSP_V3P3V goes high, about 260ms ahead of P3P3V (capture 1).
    If the SYS_ON-OFF signal is low, the MSP430 will turn off the 15V power input of the DLP system.
    When the MSP430 detects the power-on signal, that is, the SYS_ON-OFF signal goes high, it turns the power input of the DLP system on.

    capture 1: CH1--MSP_V3P3V, CH2--P3P3V, approximately 260ms difference
    capture 2: CH1--MSP_PROJ_ON, CH2--P3P3V, approximately 12ms difference
    capture 3: CH1--MCU_SW_ONOFF, CH2--MSP_V3P3V, rising simultaneously

    When the MSP430 detects the HOST_IRQ signal within 12ms after the MSP_PROJ_ON goes high,
    because the P3P3V has not gone high and the HOST_IRQ signal is low,
    the MSP430 will incorrectly assume that 3439 is initialized and then configure it through I2C.
    >I noticed you mentioned you are using 15V DC.. Is there any reason not to using 19V DC ?
    Since the 19V adapter that meets our product requirements was not found, the design was changed to a 15V power input.
    Thanks,
    JingMingJun
  • Hi JingMingJun,

    Please correct/adjust the 260ms delay for MCU_SW_ONOFF. It may be the cause that MCU_SW_ONOFF signal is triggring before setup the MCU and the interrupt to MCU might get missed.

    Thanks,
    Navneet