Monitoring current and voltage

[engr_joni_ee]

I have found INA226 that can monitor the current using a shunt resistor that can be added either on high side of the load or low side of the load.

I am wondering about the value of the shunt resistor on the high side of the load. There is a DC to DC converter providing 4 A current with the supply voltage of 5V. Some LDOs are connected to the output of LDOs supplying power to several ICs on the board. We actually want to measure the total current at the output of the DC to DC converter. Few tens of mV drop in the supply voltage is not a problem. How do we calculate the suitable value of the shunt resistor and of what power rating.

The power is 20 Watt.
P = V x I
P = 5 x 4
P = 20 Watt

V = I x R
...
...

 

[KlausST]

P = V x I

this is always true.

but P_R = V_R x I_R

The R (shunt) is connected in series with the load ... thus the load current is the same as the shunt current.
BUT: the voltage across the resistor never is the full supply voltage of 5V. The shunt voltage V_R = I_R x R, where I_R = I_load
Thus: V_R = I_load x R

***
No datasheet link, no sketch --> no answer.

You eventually need to learn (as a long term member) to do some research on your own ... and some " + - * / " math on your own.

Klaus

 

[engr_joni_ee]

Here is the datasheet INA226.

https://www.ti.com/lit/ds/symlink/ina226.pdf?ts=1708325550014&ref_url=https%253A%252F%252Fwww.google.com%252F