Which chip? The NB679 or the RK3399?
Input voltage limits
24V. Limit is 20V. HMMMM.
It was said multiple times here, that users even unsure, that 20V is alright for RockPi and here you are. Using 24V.
Like, why? Tell me, why?
With EN connected to VCC via a 10/5.1 Ohm divider, and EN max voltage being 4.5V, my calculation says that VCC max is not 9V but 4.5/5.1*(5.1+10) = 13.32V
I am just saying this because i wanted to power the rockpi4 from a PC power supply 12V line, so that i can more safely power 2.5" HDD attached to the rockpi4 USB3 ports. Should be a sae setup, also the radxa diagram has labelled VCC with 12V.
Alas, no help for when you want to run it with > 20V.
the nb679, C1 removed. R3, R4 Adapted to 24V
Since I want to use it as a PLC, it must be 24V fixed.
9v, 12V are not an advantage as PLC operation.
Correct. AFAICT 12V operation is totally fine.
C1 removed, not replaced? Doesnât seem like a good idea to me. You need C1. Read page 15 ff. of the NB679 datasheet.
Is R1 fuckered or does it still work?
What voltage divider did you use? Between 1.4V to 1.8V on the EN pin will enable USM mode. Not sure if that would interefere with something (it shouldnât, but âŚ).
I need a pi that is 24V fixed, since the hardware then only works with 24v.
âB&R X64â bus system.
The Pi is unfortunately in the press.
Sorry my english is a bit bad
Understand the purpose of that capacitor, its there to handle the high but discontinuous current demands of the converter. A good quality power supply and low impedance wires, and that capacitor isnât all that important. Its much more important for power supplies that are marginal, or wires that are relatively high impedance.
I confirm applying 20V through USB-C with a connector breakout board like the one
makes some damage. VCC12V became shorted to ground by NB679GD. My board is Rock PI 4C v1.2. Firstly, I thought that capacitor C90002 was shorted due to its voltage rating of 16V. But it turns out it was the NB679GD that was faulty. The only explanation I see is that the voltage divider formed by R90006 and R90315 apply around 6.75V on pin EN at 20V for VIN. EN pin is rated for 4.5V max. A better design would have been to replace R90315 with a 3.3V zener.
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I fried my NB679GD with a 20V supply too. I can still use my Rock Pi 4A after I de-soldered the NB679GD and connected the input to the 5V rail directly. But I think it is urgently needed that the specification or that voltage divider and the capacitors are adjusted. More people will damage their devices and might not be able to fix it.
As it is the max supply voltage is 13V!!!
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