FXA1012

One of the purposes of VPS is to drain the holes that are generated during exposure of the sensor to light. Free electrons are either transported to the VRD connection and, if excessive (from overexposure),free electrons are drained to VNS. No current should flow into VPS. During overexposures a total current 0.5 to 1mA through VPS may be expected. The PNP emitter follower in the circuit diagram (figure 9) serves these current requirements.

VNS drains superfluous electrons as a result of overexposure. In other words, it only sinks current. During overexposures a total current of 0.5 to 1mA through VNS may be expected. The NPN emitter follower in the circuit diagram meets these current requirements.The clamp circuit, consisting of the diode and electrolytic capacitor,enables the addition of a Charge Reset (CR) pulse on top of an otherwise stable VNS voltage. To protect the CCD, the current resulting from this pulse should be limited. This can be accomplished by designing a pulse generator with a rather high output impedance.

The FXA 1012 is a colour frame-transfer CCD image sensor designed for consumer digital photography applications. The combination of high speed and a high linear dynamic range of over 10 true bits makes FXA 1012 the perfect solution for use in compact high quality imaging applications. Two modes of operation provide both a monitoring image for LCD screens, and a full resolution, zero-smear still image with excellent colour rendition. The device structure is shown in figure 1.