07-11-2019, 11:11 PM
(This post was last modified: 07-11-2019, 11:13 PM by Nikolay_Po.)
Here are the diagrams of power on at pin 34 of RK808 power management system.
This is a startup from Pine64 12V 3A power supply:
Blue is voltage on 34pin of RK808 "VDC", yellow is system power voltage VCC_5V0_SYS
![[Image: attachment.php?aid=1380]](https://forum.pine64.org/attachment.php?aid=1380)
This is a startup with Pine64 12V 5A power supply:
![[Image: attachment.php?aid=1381]](https://forum.pine64.org/attachment.php?aid=1381)
A close-up:
![[Image: attachment.php?aid=1382]](https://forum.pine64.org/attachment.php?aid=1382)
It is seen that in both cases the VDC pulse is higher than 0.6V (higher than 0.6 screen cells) and longer than 100ms (longer than 1 screen cell).
RK808 power management system power plug-in detection time, TdbPLUG_IN declared as "typical", 100ms, with no maximum value. Pulse length on scope diagram is about 170..175ms. 70% margin from 100ms. Should be OK. But only in case of X5R dielectric for C204 1uF capacitor.
For initial question of @thomas88 and @TheWiley I'd recommend to look at the LEDs on the board and Ethernet connector at the moment of power plugging in. Will they blink somehow? If it is not a hardware problem, may be it is a software one?
Also I'd check the turn on with different board temperature. In case of different dielectric of C204 capacitor, the capacitance drift from voltage and temperature may significantly decrease the pulse length. In conjunction with unknown TdbPLUG_IN higher limit, turn on pulse may be shorter than actual TdbPLUG_IN time.
In other words, the design seems to me OK but two things need to be ensured: 1) C204 should be X5R or X7R dielectric, not Y5V/Z5U. 2) TdbPLUG_IN top limit should be defined by Rockchip as an IC manufacturer (may be I just don't have last RK808 datasheet).
This is a startup from Pine64 12V 3A power supply:
Blue is voltage on 34pin of RK808 "VDC", yellow is system power voltage VCC_5V0_SYS
This is a startup with Pine64 12V 5A power supply:
A close-up:
It is seen that in both cases the VDC pulse is higher than 0.6V (higher than 0.6 screen cells) and longer than 100ms (longer than 1 screen cell).
RK808 power management system power plug-in detection time, TdbPLUG_IN declared as "typical", 100ms, with no maximum value. Pulse length on scope diagram is about 170..175ms. 70% margin from 100ms. Should be OK. But only in case of X5R dielectric for C204 1uF capacitor.
For initial question of @thomas88 and @TheWiley I'd recommend to look at the LEDs on the board and Ethernet connector at the moment of power plugging in. Will they blink somehow? If it is not a hardware problem, may be it is a software one?
Also I'd check the turn on with different board temperature. In case of different dielectric of C204 capacitor, the capacitance drift from voltage and temperature may significantly decrease the pulse length. In conjunction with unknown TdbPLUG_IN higher limit, turn on pulse may be shorter than actual TdbPLUG_IN time.
In other words, the design seems to me OK but two things need to be ensured: 1) C204 should be X5R or X7R dielectric, not Y5V/Z5U. 2) TdbPLUG_IN top limit should be defined by Rockchip as an IC manufacturer (may be I just don't have last RK808 datasheet).