I had installed/plugged 4 HSM (2 old V1 and 2 new V2 ) on my Server and after a while the power supply “burned” - After years of proper running, I am pretty sure that the load of the HSM finally killed it. So I wonder what is the real power usage of the NK Keys ? I reviewed the data sheet and have not seen a dedicated answer. The data sheet declares for a HSM e.g. USB A, Ver 1.1 , what would lead to a maximum of 100mA. Is that the limit ? ( also during heavy load ?)
To be clear: it was not the NK HSM or the fact that I had plugged every available USB slot with a NK HSM. The power supply was anyhow on the edge as I hacked the Server with more disks and network than usual and did not upgraded the power supply to the right level. But as it worked now several years, the final constat load of the NK’s might have killed the power-supply ( MTBF could always happen ).
I don’t have exact numbers yet but I’m pretty sure Nitrokey’s power
consumption doesn’t exceed 100 mA. We will do some measurements in two
weeks time and respond with details here.
Hi!
Looking theoretical consumption side, MCU alone should not exceed 51 mA [1].
HSM smart card is based on JCOP 3 platform, but I could not find any power definitions for it. Depending on class it might take maximum either 80 or 200 mA.
[1] STM32F103xB specification, page 42, 5.3.5 Supply current characteristics, Table 13. Maximum current consumption in Run mode, code with data processing running from Flash: 72 MHz -> 50 / 50.3 mA.
Yeah, the first I also have read. I think a test-cycle with a USB power meter will give you a first guess. It also depends what else you have enabled on the circuit. 200mA would be for USB1,1 too much. For USB 2 - you wouldb need to request from the Host first if it is more than 100mA.
Also the NK Storage has two cards - so crypting and writing on the SD card might consume more than 100mA - hey , time to change to USB-C
Yes, as a frame - but you would also request more than 100mA from the Host BEFORE you coudl consume it. Alt least that is the specification:
9.2.5.1 Power Budgeting
USB bus power is a limited resource. During device enumeration, a host evaluates a device’s power requirements. If the power requirements of a particular configuration exceed the power available to the device, Host Software shall not select that configuration.
USB devices shall limit the power they consume from VBUS to one unit load or less until configured. Suspended devices, whether configured or not, shall limit their bus power consumption as defined in Chapter 7. Depending on the power capabilities of the port to which the device is attached, a USB device may be able to draw up to five unit loads from VBUS after configuration.
