[C5535] Confirm the mean of "all power supplies" in RESET release timing.

Hi Kaka-san,

Below is my response.

The USB_LDO is not enabled while reset status. Right?

VK: Yes that's correct.

Would you please show me the target power domains which it means the  "all power supplies " in nRESET timing on datasheet?

VK: With respect to C5535 datasheet, pl read as. " The external reset signal on the RESET pin must be held low until all of the external power supplies reach their operating voltage conditions." This means all external supplies (supplied to device) need to reach valid voltage levels before reset pin is released". This will be updated in datasheet too.

[Background ] The USB domain has power-up sequence and need to be satisfied with this. But the USB_LDO is not enabled at reset timing. And this LDO is controlled by register on C5535. In order to be enabled this LDO, we need to run the initialization program for this. It seems that this is impossible because the nRESET is held low until USB_VDDA1P3 or USB_VDD1P3 reach their operating voltage condition even though the USB_LDO is disabled.

VK: Yes this is right, USB LDO is not enabled until its software configured, which happens only after reset and boot sequence process.

Hope this clarifies.

Regards

 Vasanth

Hi Kaka-san,

Yes your explanation is correct. What I meant is external supply needs to be at right voltage before you release the reset. For example (In your case) external supply of 3.1V should have reached the right threshold level.

Hope this clarifies.

Regards

 Vasanth