nRF5340 - VBUS pin issues

RE: nRF5340 - VBUS pin issues

Gabriele — Mon, 12 Jul 2021 14:47:56 GMT

Ok, I see using a switch is unavoidable.
Thanks.

RE: nRF5340 - VBUS pin issues

Stian Røed Hafskjold — Mon, 12 Jul 2021 14:31:29 GMT

When VBUS is not powered on the nRF52, there will be flowing current through the internal ESD diodes from D+/D- to VBUS. The current will then only be limited by the pull down resistor on VBUS to GND. So that's not a solution. You will at least have to power VBUS, but again, there will flow current to ground in the milliamp range.

RE: nRF5340 - VBUS pin issues

Gabriele — Fri, 09 Jul 2021 10:03:26 GMT

This is the circuit.
The question is can IC communicate with PC when nRF5340's VBUS is 0V ?
I want to avoid a USB switch.
Consider that a pull down to GND is not a short to GND.

RE: nRF5340 - VBUS pin issues

Stian Røed Hafskjold — Fri, 09 Jul 2021 09:42:25 GMT

Do you mean VDD = 0V and VBUS=5V? nRF53 VDD is forced to 0V and the VBUS and D+/D- lines are shared with another USB device, leaving VBUS at 5V?

If VBUS is forced to GND there will be a short circuit between GND and D+/D-

RE: nRF5340 - VBUS pin issues

Gabriele — Fri, 09 Jul 2021 06:29:55 GMT

Thank you Stian.
Now, suppose to have a situation where nRF5340's pin VBUS = 0V, and another IC with its own USB Device interface attached on the same D+/D- bus.
Will the nRF5340's internal diodes plus resistors disrupt the bus communication between the host and the IC?
I know this is a difficult question, but I'm pretty sure you have an answer also for this.

RE: nRF5340 - VBUS pin issues

Stian Røed Hafskjold — Thu, 08 Jul 2021 14:35:02 GMT

Hi,

The nRF5340 cannot be damaged if VBUS is powered while VDD and VDDH are forced to 0V. However, the D+/D- are not floating, they are pulled towards VSS by a diode and a series resistor. The resistance is ~100kohm if VDD=0V, and in the 1kohm range if VDD is present.

RE: nRF5340 - VBUS pin issues

Gabriele — Sun, 04 Jul 2021 19:40:13 GMT

Hello Stian,

any news on this ?

RE: nRF5340 - VBUS pin issues

Gabriele — Wed, 30 Jun 2021 07:56:56 GMT

When disabled, my supply voltage regulator is grounded to 0V.

RE: nRF5340 - VBUS pin issues

Stian Røed Hafskjold — Tue, 29 Jun 2021 11:20:15 GMT

When you say VDD = VDDH = 0V, does that mean grounded or open?