My customer uses TPS62239 with the Murata LQM21PN2R2MC0 inductance 2.2uH 600mA.

When he calculates the DC output load regulation 0.001%/mA , he finds 5mV; but when he measures the output voltage for Iout = 500mA ,he finds 10mV with Vin=5V. Question:

Do you you think the measured value is good(reasonable deviation)?

What is the mean of the Output voltage accuracy between -40°C to +85°C?

Do you think that in the specifications output voltage accuracy we can include the dc output load regulation. ex: output voltage accuracy -40°C to +85°C : +-2.5% => +-25mV dc output load regulation 0.001%/mA => for 500mA we have 5mV. What is the consideration to do?Max=> +-25mV or Max (25mV+5mV) => 30mV.

The load regulation is specified at 0.001%/mA typical at the conditions of Vin = 3.6V, Vout = 1.8V, and power save mode disabled.  Since your conditions are different, you may get a different value for the load regulation.  However, I would expect it to be close to 0.001%/mA and the 0.002%/mA that your customer is measuring is certainly close to the typical value spec'd in the datasheet.  Also, make sure that the customer is measuring the current and voltage with high precision meters and measuring the voltage right at the output of the IC.  Any inaccuracies in the maters or extra voltage drop from the board trace can certainly affect the measurement by 0.001%/mA.

The meaning of the output voltage accuracy of +/-2.5% is that at the conditions specified, Vin = 3.6V, power save mode disabled, and no load, the output voltage will be within the setpoint by +/-2.5% on all devices and over the said temperature range.  This spec does not include load regulation, as the load is set to 0 in the test conditions.

Yes, the total accuracy is the accuracy at no load (+/-2.5%) plus the load regulation of 0.001%/mA typical.

You can find the typical load regulation at your Vin/Vout conditions in figures 14 and 15 in the datasheet.