Performance of a 2048 × 2048 Pixel Three-Side-Buttable CCD Designed for Large Focal Planes in Astronomy

Abstract

TH78997M is a 2048 × 2048 pixel full-frame CCD sensor featuring 15 × 15 micron pixels, MPP operating mode, four parallel outputs and buttability on three sides. This new device makes it possible to build very large focal plane detectors for telescopes (two × n butted CCDs) with less than a 25 dead pixel zone between adjacent sensors. Other features are high full-well capacity (typically 180 Ke−) and very low dark current thanks to four phase MPP clocking which allows a very long exposure time together with a high S/N ratio.The readout of a complete frame is achieved through four parallel outputs running at frequencies ranging from ten KHz up to five MHz per output. The four on-chip amplifiers have been designed to be completely user controlled and to meet most of terrestrial and spaceborne astronomy requirements: very low noise (less than 4e− at 50 KHz, −40 degrees C), very low power consumption (150 micro-W/amplifier at 10 KHz/output), linearity better than 0.5% together with high conversion factor (4.2 micro-V/e−) over 2.5 V output range. The packaging of the device is compatible with the good flatness of the chip and with the low parasitic “cosmic event” rate thanks to specific care in selecting the packaging material.