An Applications Engineer demonstrates how a simple resistor divider can be used to measure current and power with the new ISL28022 digital power monitor.


For the second circuit, I'm gonna demonstrate a simple resistor divider. This will demonstrate the current in the power readings for the ISL28022.

For this circuit, I have VBUS connected to a top of a resistor divider with the VINP. The shunt resistor, who has 10ohms, this could be used as a shunt resistor to measure current, and then the load would be 1k, as you can see here, and the VINM is connected between the 10ohm resistor and the 1k ohm resistor.

So I've connected the circuit that I gave you an illustration on to Site 2. I have 5V applied to VBUS. If you noticed, I had a 10ohm shunt resistor and 1,000ohm load resistor, so it's roughly a 1-to-100 ratio. As you can see, is that the VBUS is at 5V and the VSHUNT is at 50mV.

What you can see here is I'm gonna lower the...make it more accurate again. You can see that ratio is illustrated here. Now to measure the current, just press the Current checkbox, enter in the resistor value of your shunt, and press okay. The reading that I see as the current matches what I see on the DMM that I have here.

To measure the power, just click on the Power button or the Power box, and the ISL28022 will calculate the power, just like it calculates the current internally without using microcontroller commands. And to just make it easy for us, you can see 5 x 5, V x I equals Power, is 25. Now that looks right and if you lower this to 1V, as you can see, 1 x 1 = 1.