Q: How to understand the initial accuracy 0.2% for MAX6033B? If the input voltage, temperature is constant, will the output be same for each POR? Or it changes randomly?
A: Initial accuracy speaks for itself. It is the value set by any trimming. One can take a part off the shelf, connect it in a test circuit in automatic test equipment (ATE), and measure the output voltage. The measured value should be within the initial accuracy tolerance specified in the data sheet. This specification is usually for room temperature only, with a defined input voltage and load current. It provides a starting point for most of the other specifications. Initial accuracy tolerance can be affected by package stress, so proper control of the solder temperature profile is essential and twisting of the PCB must be kept to a minimum. Because package stress may start to change the unpowered part on the shelf, the initial accuracy tolerance may be subject to slight drifts; This is one reason why many industries, notable the military, require new products with date-coded parts to be less than a certain age.
For example, MAX6033B, 2.5V output. The test condition should be same as datasheet as below. And then, you can get the test data for initial accuracy. Usually, when these test conditions are fixed, the initial accuracy for each POR will be same. Usually, its initial error can be calibrated by system softward.
ELECTRICAL CHARACTERISTICS—VOUT = 2.500V
(VIN = 5V, COUT = 0.1µF, IOUT = 0A, TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1)