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TMS570LS1227: What is the internal circuit about 41 pin

Sherry Liang
Genius 10255 points
Part Number: TMS570LS1227

Dear team,

When the MCU is powered down, there will be 2.9V (normal power) at point A, and 2.2V at point B, and at this time the VCC pin of TMS570 will be about 1V. Why is it? Could you please tell me what is the internal structure of the PIN41 pin?

Thanks & Best Regards,

Sherry

  • 0
    TI__Guru**** 186196 points

    Hello,

    How did you power down the TMS570: cut the power supply (1.2 and 3.3) to MCU or just put the MCU to sleep mode? Is there power for other devices on the same PCB? 

  • 0 in reply to QJ Wang
    TI__Genius 10255 points

    Hi QJ,

    Sorry for the late reply!

    The power down means cut the power supply(1.2 and 3.3). 

    Yes, there is other power for other device in the same PCB. 

    Thanks & Best Regards,

    Sherry

  • 0 in reply to Sherry Liang
    TI__Guru**** 186196 points

    Hello Sherry,

    At the input pins on TMS570 device, there are diodes to protect the chip from ESD. These diodes connect to the supply rail of the device.

    If you drive a logic signal into a pin when the device is not powered it will attempt to power via the diode. This might not cause damage, but it will affect the power on reset circuitry, so the device will not power up correctly when power is available.