UCD9248 rail 1 does not seem to soft-start

We're bringing up a board with four UCD9248 parts. Excerpts from our schematics are available (privately) on request -- but it's a pretty standard design, borrowing verbatim from the Xilinx VC709 evaluation board.

On a few of our supplies, we're unable to get the first rail (which also happens to be the lowest-voltage rail; 1.0V on one UCD9248, and 0.9V on another) to soft-start. Attached is a typical trace, showing a quick up-slew and a substantial overshoot. We have used "magic" calibration for the control loop, so this should be a vanilla use of the TI tools for the device.

Any suggestions? We are probably able to tolerate this level of overshoot, but the lack of soft-start is making us hesitant to hook up expensive downstream parts to these supplies. (The supplies are currently mostly unloaded, although a few experiments didn't show the problems to be load-dependent.)

thanks,

Graeme2746.ucd9248.xml