CCD 191 6000 Element Linear Image Sensor FEATURES • • • • • • • • • • • • 6000 x 1 photosite array µm photosites on 10µ µm pitch 10 µm x 10µ Anti-blooming and integration control Enhanced spectral response (particularly in the blue region) Excellent low-light-level performance Low dark signal Very high responsivity High speed operation Dynamic range typical: 15000:1 Over 3 V peak-to-peak outputs Special selection available - consult factory AR coated window GENERAL DESCRIPTION The CCD191 is a 6000 element line image sensor designed for scanning applications which require very high resolution, high sensitivity and very wide dynamic range. Incorporation of on-chip anti-blooming and integration controls allow the CCD191 to be extremely useful in industrial measurement and control environments, or in environments where lighting conditions are difficult to control. The CCD191 is a third generation device having an overall improved performance compared with first and second generation devices, including enhanced blue response and excellent low light level performance. The photoelement size is 10µm (0.39 mils) x 10µm (0.39 mils) on 10µm (0.39 mils) centers. The device is manufactured using Fairchild Imaging’s advanced chargecoupled device n-channel isoplanar buried-channel technology. Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD191 FUNCTIONAL DESCRIPTION Prescan Reference — Video output level generated from shift register cells which provides a reference voltage equivalent to device operation in the dark. This permits use of external DC restoration circuitry. The CCD191 consists of the following functional elements illustrated in the Block Diagram and Circuit Diagram. Photosites — A row of 6000 image sensor elements separated by a diffused channel stop and covered by a silicon dioxide surface passivation layer. Image photons pass through the transparent silicon creating hole-electron pairs. The photon generated electrons are accumulated in the photosites. The amount of charge accumulated in each photosite is a linear function of the incident illumination intensity and the integration period. The output signal will vary in an analog manner from a thermally generated background level at zero illumination to a maximum at saturation under bright illumination. Dynamic Range — The saturation exposure divided by the RMS temporal noise equivalent exposure. Dynamic range is sometimes defined in terms of peak-to-peak noise. To compare the two definitions a factor of four to six is generally appropriate in that peak-topeak noise is approximately equal to four to six times RMS noise. RMS Noise Equivalent Exposure — The exposure level that gives an output signal to the RMS noise level at the output in the dark. Two Transfer Gate — Gate structures adjacent to the row of im- Saturation Exposure — The minimum exposure level that will provide a saturation output signal. Exposure is equal to the light intensity times the photosites integration time. age sensor elements. The charge packets accumulated in the photosites are transferred in parallel via the transfer gates (φX) to the transport shift registers whenever the transfer gate voltages go high. Alternate charge packets are transferred to the A and B transport registers. Charge Transfer Efficiency — Percentage of valid charge information that is transferred between each successive stage of the transport registers. Two Analog Shift Registers — The transport shift registers are used to move the light generated charge packets delivered by the transfer gates. (φ1A, φ1B, φ2A, φ2B) serially to the charge detector/ amplifier. The parallel layout of the last elements of the two transport registers provides for simultaneous delivery of charge packets at the output amplifiers. Responsivity — The output signal voltage per unit exposure for a specified spectral type of radiation. Responsivity equals output voltage divided by exposure. Total Photoresponse Non-uniformity — The difference of the response levels of the most and the least sensitive element under uniform illumination. Measurement of PRNU excludes first and last elements. A Gated Charge Detector/Amplifier — Charge packets are transported to a precharge capacitor whose potential changes linearly in response to the quantity of the signal charge delivered. This potential is applied to the input gate of the two-stage NMOS amplifiers producing a signal at the output “VOUT” pin. Before each charge packet is sensed, a reset clock (φRA, φRB) recharges the input node capacitor to a fixed voltage (VRDA, VRDB) Dark Signal — The output signal in the dark caused by thermally generated electrons that is a linear function of the integration time and highly sensitive to temperature. Saturation Output Voltage — The maximum usable signal output voltage. Charge transfer efficiency decreases sharply when the saturation output voltage is exceeded. Integration and Anti-Blooming Controls — In many applications the dynamic range in parts of the image is larger than the dynamic range of the CCD, which may cause more electrons to be generated in the photosite area than can be stored in the CCD shift register. This is particularly common in industrial inspection and satellite applications. The excess electrons generated by bright illumination tend to “bloom” or “spill over” to neighboring pixels along the shift register, thus “smearing” the information. This smearing can be eliminated using two methods: Integration Time — The time interval between the falling edge of any two successive transfer pulses (φX). The integration is the time allowed for the photosites to collect charge. Exposure Time - The time interval between the falling edge of the two transfer pulses (φX) shown in the timing diagram. The exposure time is the time between transfers of signal charge from the photosites into the transport registers. Anti-Blooming Operation: A DC voltage applied to the integration control gate (approximately 1 to 3 volts) will cause excess charge generated in the photosites to be diverted to the anti-blooming sink (VSINK) instead of to the shift registers. This acts as a “clipping circuit” for the CCD output. Pixel - A picture element (photosite). CCD191 CIRCUIT DIAGRAM Integration Control Operation: Variable integration times which are less than the CCD exposure time may be attained by supplying a clock to the integration control gate. Clocking φIC reduces the integration time from tEXPOSURE to tINT. Greater than 10:1 reduction in average photosite signal can be achieved with integration control. The integration-control and anti-blooming features can be implemented simultaneously. This is done by setting the φIC, clock-low level to approximately 1 to 3 volts. DEFINITION OF TERM Charge-Coupled Device — A Charge-coupled device is a semiconductor device in which finite isolated charge-packets are transported from one position in the semiconductor to an adjacent position by sequential clocking of an array of gates. The charge-packets are minority carriers with respect to the semiconductor substrate. 2 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD191 BLOCK DIAGRAM CCD191 3 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD191 4 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD191 5 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD191 TIMING DIAGRAM 6 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD191 TYPICAL PERFORMANCE CURVES 7 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD191 PHOTOELEMENT DIMENSIONS TEST LOAD CONFIGURATIONS CCD191 PACKAGE OUTLINE DEVICE CARE AND OPERATION ORDER INFORMATION Glass may be cleaned by saturating a cotton swab in alcohol and lightly wiping the surface. Rinse off the alcohol with deionized water. Allow the glass to dry, preferably by blowing with filtered dry N2 or air. Order CCD191DC where “D” stands for a ceramic package and “C” for commercial temperature range. It is important to note in design and applications considerations that the devices are very sensitive to thermal conditions. The dark signal dc and low frequency components approximately double for every 5º C temperature increase and single-pixel dark signal non-uniformities approximately double for every 8º C temperature increase. The devices may be cooled to achieve very long integration times and very low light level capability. 8 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500