Hi,
The datasheet describes the power up sequence as follows
...
3. All static 1.8V IO supplies (DVDD18, DDR_DVDD18, USB0_VDDA18, USB1_VDDA18 and SATA_VDDR) and any of the LVCMOS IO supply groups used at 1.8V nominal (DVDD3318_A, DVDD3318_B, or DVDD3318_C).
4. All analog 3.3V PHY supplies (USB0_VDDA33 and USB1_VDDA33; these are not required if both USB0 and USB1 are not used) and any of the LVCMOS IO supply groups used at 3.3V nominal (DVDD3318_A, DVDD3318_B, or DVDD3318_C).
There is no specific required voltage ramp rate for any of the supplies as long as the LVCMOS supplies operated at 3.3V (DVDD3318_A, DVDD3318_B, or DVDD3318_C) never exceed the STATIC 1.8V supplies by more than 2 volts.
...
If a customer brings up the 1.8V rail (after RTC and Core supplies certainly), while the 3.3V is still down, there is an interesting ramp visible on the 3.3V rail, which starts at the time when 1.8V ramps. The 3.3V rail is pulled up by the 1.8V rail. Pictures attached. This however does not violate the datasheet sequencing requirement as stated above.
Questions:
(1) Would this ramp on 3.3V based on the 1.8V ramp be expected? Is there a C6748 device level reason for it?
(2) Are there any reliability concerns with this behavior?
Regards,
--Gunter
