  We develop the vertex detector for the international linear collider (ILC)
using the FPCCD (Fine Pixel CCD), whose pixel size is 5 x 5 um2. Together with
the FPCCD sensor, a prototype of the readout ASIC was developed in 2008. The
readout ASIC was confirmed to work correctly at slow readout speed (1.5
Mpix/sec). In this letter, we describe the status of the performance study for
the readout ASIC.
