TMS320F28374S: XRS signal pulled down then restored to 1 while the 1.2V(VDD) and 3.3V(Vdd3vfl/vddio) are powered off

Hi Benjamin,

When the device powers up, the threshold for the POR triggered reset is untrimmed.  This untrimmed reset threshold is lower than the trimmed level.  Shortly after powering up, trims are loaded and the reset threshold is increased to be trimmed and closer to the device operating voltage range.

What will happen if the supply voltage is held between the untrimmed and trimmed reset thresholds (or is ramping slowly):

• Supply voltage is high enough to allow device to start powering up
• During the power-up process trim is loaded
• Supply voltage is now below the reset threshold, so the device resets

This isn't a concern for the C2000 device; the device will not begin executing until the trim is stable and the supply voltage is above the trimmed threshold.  However, if these resets propagate to other devices on the board or in the system, you may want to qualify the reset signal before passing it on to other ICs or components.

Hi Devin,
This issue is reported at power off state, not the power on state.
Do you mean, during the power off state, the power supply is high enough to allow device to start powering up if the power supply kept flat?
what's the voltage range for device to decide to start powering up?

Expect for your reply, thanks.

Best Regards
Benjamin

Hi Benjamin,

The device doesn't really know or care if the voltage is ramping up or down. As long as the voltage is between the untrimmed and trimmed trip threshold, the device will try to start, but fail once the trims are loaded.

Hi Devin,
What's the voltage range of untrimmed and trimmed? what's the range of trip threshold?
Expect for your reply, thanks.

Best Regards
Benjamin

Hi Benjamin,

The device can attempt power up as low as 2.1V (typically 2.5V). The trimmed trip range should be between 2.8V and 3.0V.