MPQ4487 line drop compensation


I had bought new EV Kit for MPQ4487 (EVQ4487) for evaluation.
I had tried to have line drop compensation as attached file.

But I had 40mV at 2.4A for line drop compensation, but seems small ( data sheet says 90mV).
Would you please check whether my measurement is wrong or correct.

I attached test method and result.
Please advise.
Thank you

Hi Kanji,

We’ll take a look at this and let you know our comments.

Hi Kanji,

From your set up and linear data, it looks like the measurement is close to accurate. The data sheet’s spec for line drop compensation is within spec of what you are getting.
Another test you may do is to apply load to USB1 and USB2 at the same time and see if it changes. If it does, then that would be due to the accuracy of either current sense.

In addition to this, you should measure at the buck output voltage since there is an IR drop after the USB switch at heavy load.

Dear Cecilia san

Thank you for your advise !

I had tested again according to your advice.
I understood that there are IR drop after USB switch as your comment.
Vout was approx 100mV higher than USBx when Iout=2.4A.

Here is my result for your reference.

(Case 1) Both No load
USB1  ;5.154 V whenUSB2  ;5.156 V
VOUT ; 5.156 V
(Case 2) USB2 2.4A /USB1 No load
USB1 ;5.251 V
USB2 ;5.198 V
VOUT1 ;5.254V

(Case 3) USB1 2.4A /USB2 No load
USB1  ;5.1901V
USB2  ;5.246 V
VOUT  ;5.247V

(Case 4)  USB1&USB2 both 2.4A
USB1 ;5.195 V
USB2 ;5.196 V
VOUT ;5.256 V


Thank you and with my best regards


I have a mistake / some TYPO in my previous data.
Please forget previous data.

( I had used Fluke287 tester for USB1 and VOUT data. It was bad accuracy…
Changed all voltmeters to HP 34401A, but tolerance between multimeter should be 1~1.5mV )


(Case 1) Both No load

USB1 5.154 V
USB2 5.153 V
VOUT 5.154 V
(Case 2) USB2 2.4A,  USB1 No load

USB1  5.252 V
USB2  5.195 V
VOUT1 5.252V

(Case 3) USB1 2.4A , USB2 No load

USB1  5.191 V
USB2  5.243 V
VOUT  5.243 V

(Case 4) USB1/USB2 both 2.4A

USB1 5.195 V
USB2 5.194 V
VOUT 5.195 V

Hi Kanji,

This looks good!