As for your REF02 Vref,
If REF02 short Vout to GND, then what is the output voltage action?
1) drop to GND directly soon
2) when over the some load for a while, and drop to GND
Otherwise another action?
Any time that any output is shorted to ground, the output voltage will immediately go to ground potential, or zero volts relative to that ground. The exception, of course, is when the "short" is not zero Ohms. There are other considerations for output short circuiting. A look at the product data sheet page 4 indicates that the output current is limited to 30mA when the output is shorted to ground and the supply voltage is 15V (The short circuit current may be higher with higher supply voltages). Page 6 of the data sheet, in the Absolute Maximum Ratings Table, indicates that the output can be shorted to ground indefinitely without damaging the device. However, it should be noted that, at elevated ambient temperatures, the self heating caused by the power dissipation when the output is shorted just MIGHT raise the die temperature enough to be a problem. This would seem unlikely, but it does seem possible when you look at the thermal capability of the device. With a supply voltage of 30V (max for the product is 36V) and 30 mA output short circuit current, ignoring the quiescent current, we find that the power dissipation of the device is 900mW. The junction to ambient thermal resistance of the device ranges from 110degC/W in the TO-99 package to 170degC/W in the PDIP. The rated maximum die temperature is 150degC, and, for safe die temperatures with extended short on the output, the maximum ambient temperature is limited to about 51degC in the TO-99 package. Of course, a heat sink on the the device will allow for higher ambient temperatures with an extended short on the output and being mounted on a PCB will provide some amount of heat sinking, but whether it is enough depends upon the amount of copper on which the device is mounted). In the TO-99 package, the ambient temperature should be limited to about -3degC to ensure that the die temperature is not exceeded. I may be over cautious, but better safe than sorry. Furthermore, careful design will result in better overall circuit reliability.