Board for power measurement


#1

hello,

I would like to measure current and voltage of CPU, GPU and Memory individually. I have access to national instruments measuring modules. I am expecting to put my probes at the output of the regulator which supplies power to CPU, GPU and Memory. Can you recommend any board with available schematics, decent enough processor to run benchmarks and easy enough to do power measurements.

Thank you very much.


#2

Hi Naveen,

96boards usually supports power measurement but the measurement point is a general measurement point and can NOT measure power for CPU, GPU and memory individually.

Please see the Hikey doc: https://github.com/96boards/documentation/blob/master/ConsumerEdition/HiKey/AdditionalDocs/HiKey_User_Guide_CircuitCo.pdf, in the page 10 it explains J12 ~ J14 for power measurement. For CPU, GPU and memory power measurement, you could use J13 to measure PMIC total power, it includes all SoC related power. Please note one thing, Hikey board has two manufactures, one is Circuit and another is Lemaker. This doc is for Circuit version and you should check schematics for Lemaker version for these pins.

For Mediatek X20 board, you could find related info in the page:
http://www.96boards.org/documentation/ConsumerEdition/MediaTekX20/HardwareDocs/HardwareUserManual.md/, in “Power Measurement” chapter.

Thanks,
Leo Yan


#3

Thanks Leo for the reply.

Unfortunately, total SoC power measurement is not sufficient for me. I need individual power numbers.

Also, I am not expecting ready made measurement points for the same. We have good knowledge of soldering boards in house. So, I am expecting to have good schematics from which I can know where exactly I need to put my probes on. Would any of the boards from 96boards fit that bill?

Best


#4

Hi Naveen

I think it is unlikely. There are two reasons for this:

  1. Manufacturers are not required to publish the board artwork needed to mod a board in this manner. In most cases this artwork is held by the board manufacturer and you would have to approach them to negotiate over access to a copy.

  2. Downstream of the PMIC (e.g. CPU, GPU. DDR) the design constraints on the board tend be pretty aggressive and most board designers react by burying the power rails in the mid layers. So even if you did have the artwork required to locate them and somehow managed to “unbury” them the system would be unlikely to meet the PMIC design constraints. So after all the work you may simply end up with a broken board…

If you have the budget ARM’s Juno platform is quite flexible here (I suspect because it doesn’t use a mobile phone PMIC), see https://community.arm.com/docs/DOC-9321 .


Board File for Hikey960
#5

Thank you @danielt. ARMs juno platform seems to be perfect fit for my work. I have also been looking at Minnowboard Turbot schematics and it seems that the resistors have been surfaced on the board to tap. Do let me know if you know about other alternatives. I will make a evaluation and buy one of them.

The NI measuring modules to measure current has a built in shunt resistor. It also has very low input impedance (12mOhms). So, I strongly believe that it should be within the PMIC’s design constraints as the voltage drop across it is negligible.

We recently bought Nvidia Jetson TX1. But the schematics for the daughter board are not available. Also, the Thermal Transfer Plate (TTP) is applied in a special process which once taken apart cannot be put back together without specialized equipment. So, there was no access to PMIC there.


#6

Regarding PMIC stability, I’m not privy to all the details but I believe that the constraints (which will vary between PMICs) also include the reactance of the load; burying the rails gives the designers strong control over rail capacitance.


#7

Just got a quote from the suppliers of ARM Juno r2. They are charging about 9000€ (approximately 9617$). There is no academic pricing. Basically the pricing is the same for academic and commercial purposes. I was willing to go up to 2000-3000 euro. But the price tag puts it beyond my reach. I was not expecting it to be so expensive.

@leo.yan and @danielt, do you have any other board suggestions?


#8

I’m afraid I was expecting it to be that expensive… that’s why I mentioned the budget when I introduced it!

Anyhow, it if helps the Helio X20 board has inductors to help the PMIC manage the rail capacitance. These downstream of the PMIC and brought out to the surface of the board.

This might make a board mod possible although I must repeat how tricky this could be. You’ll have to desolder the inductors and connect the instrumentation and try to include sufficient inductance to the power monitoring circuit to keep the PMIC stable. In other words you risk having something that is physically very fragile and could also be electrically unstable.


#9

Hi…i am a new user here. As per my knowledge downstream of the PMIC the design constraints on the board tend be pretty aggressive and most board designers react by burying the power rails in the mid layers. So even if you did have the artwork required to locate them and somehow managed to “unbury” them the system would be unlikely to meet the PMIC design constraints.