The recent development of active pixel sensors as X-Ray focal plane arrays will place them in contention with
CCDs on future satellite missions. Penn State University (PSU) is working with Teledyne Imaging Sensors
(TIS) to develop X-Ray Hybrid CMOS devices (HCDs), a type of active pixel sensor with fast frame rates,
adaptable readout timing and geometry, low power consumption, and inherent radiation hardness. CCDs have
been used with great success on the current generation of X-Ray telescopes (e.g. Chandra, XMM, Suzaku, and
Swift). However, their bucket-brigade readout architecture, which transfers charge across the chip with discrete
component readout electronics, results in clockrate limited readout speeds that cause pileup (saturation) of bright
sources and an inherent susceptibility to radiation induced displacement damage that limits mission lifetime. In
contrast, HCDs read pixels through the detector substrate with low power, on-chip readout integrated circuits.
Faster frame rates, achieved with adaptable readout timing and geometry, will allow the next generation's larger
effective area telescopes to observe brighter sources free of pileup. In HCDs, radiation damaged lattice sites
affect a single pixel instead of an entire row. The PSU X-ray group is currently testing 4 Teledyne HCDs,
with low cross-talk CTIA devices in development. We will report laboratory measurements of HCD readnoise,
interpixel-capacitance and its impact on event selection, linearity, and energy resolution as a function of energy.