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TPS659037: Some questions

Sho Ogane
Genius 5575 points
Part Number: TPS659037

Hi team,

I have two question about TPS659037.

1.About output timing of LDOVRTC in power sequence.
  I couldn't finf LDOVRTC output timing,
  so please tell me the timing.

2.TPS659037 has OSC16MIN and OSC16OUT.
   If we don't use 16Mhz crystal, Does the power supply sequence circuit work normally?

Best Regards,
Sho

  • 0
    TI__Genius 16410 points

    Hello Sho,

    1. VRTC is always on, so it will come up with VCC (minus some dropout), and will always be on as long as VCC is supplied to the PMIC.

    2. Whether or not the crystal is required is defined by OTP.  For TPS6590376 and TPS6590377, the OSC16M_CFG bit is 0, which means the crystal is required for the device.  Please see section 6.2.2.9 of the datasheet for more details.  The device may not operate correctly if it is configured for a crystal and a crystal is not connected to the PMIC.

    Regards,
    Karl

  • 0 in reply to Karl Wallinger
    Genius 5575 points

    Hi Karl san

    Thank you for the quick response.

    I understood about  VRTC output.

    However I can't  understand the following.
    The device has 16MHz oscillator, so if external crystal is not connected to PMIC, I think it operate correctly.
    So please tell me the detail reason why it may not operate corectly, sorry.

    Best Regards,
    Sho

  • 0 in reply to Sho Ogane
    TI__Genius 16410 points
    Hello Sho,

    Regarding the oscillator, the oscillator block is enabled by OTP, and is expecting a sine wave input (generated by crystal). In the oscillator module, this input passes through a DC blocking capacitor. If a crystal is not supplied, the internal oscillator node is floating (due to the series capacitor), and therefore the input seen by the PMIC is undefined. This floating node can pick up noise, and the PMIC could see some random frequency.

    In the worst case, the PMIC will see random noise and interpret it as a clock, and this can cause issues within the PMIC, including sudden reset.

    Regards,
    Karl