Current and Voltage and the output of the regulator

[johndoe419]

Hello all,

I have a TPS62361B (http://www.ti.com/product/TPS62361B) switching regulator from texas instruments on my embedded system. The regulator does voltage scaling from 0.5V to 1.77V in 10mV steps. The maximum current at the output of the regulator is around 3A. The output of the regulator goes to the ARM processor.  I would like to measure the voltage and current at the output of the regulator (input to the ARM processor). I have NI 9215 for voltage and NI 9227 for current measurement.

1) Can I use them to measure the voltage and current at the output of the regulator?

2) Considering that the ARM processor may run sometimes at pretty low voltages when doing DVFS what is the recommended strategy to measure V and I?

3) How should the actual probes be connected? I am novice on the electronics side. So some handholding needed.

Thank you very much for your time.

[VenkatStony]

Hi

you can measure Voltage at any point of the circuit with respect to ground using voltage input NI card or module.

Check is there any measuring pont at the output of the regulator, is there? then connect Possitive of the chennel NI 9215 and GND to Board ground.

But Current measurement is some what difficult to mearure, because you need to connect NI 9227 cheannel in series with measuring point.

Regards.,

Venkat

[Henrik_Volkers]

Well, you can measure a voltage at any point on the board 🙂

But will it be the voltage of interest?

Quite high current, and voltage loss on traces .. 

So assuming you have a good PCB layout and you want to know the voltage AT the processor your need to measure it close at the processor. Looking at the datasheet of the converter two points to the layout: The feedback traces sense+- should go close to the processor to enable a voltage drop correction due to the current.  The current measurement should be done in the trace between the buffer cap/ coil and the sense + .   I would have choosen a current sense resistor directly on the PCB... however .. so keep the wires to the NI 9227 as short as possible. The 12mOhm sense resistor will give you a 36mV drop at 3A , that will be compensatet by the converter if the sense + is wired as noted.

Next: 50kHz samplerate aka ~22kHz bandwidth is much to slow for processor current monitoring .. the processor can do ten power consuming tasks inbetween two samples and even fall asleep half of the time 😉    not talking about the 2.5 MHz switching frequency of the converter, however an educated guess migth be possile 😄