level (the signal level beyond which additional signal charges are
drained away). A higher VSTOR bias results in a higher anti-
blooming level.
Transfer
The TCK clock controls the transfer of electrons from the stor-
age well into two discrete readout registers for alternating
odd/even pixel readout. Transfer is from the storage wells into
the CR1 phases of the readout registers. The readout registers
are then used to serially shift the charge packets to the two
high-speed low-noise output amplifiers.
The two readout registers are pseudo-2-phase buried-channel
CCD shift registers. The CR1x and CR2x phases are comple-
ments of each other. Each of these two phases has a storage
(CRxS) and a barrier (CRxB) gate. The storage and barrier gates
of each phase are clocked in phase (i.e., CR1S is clocked in
phase with CR1B, and CR2S is clocked in phase with CR2B).
The only difference between the storage and barrier phase
clocks is the bias levels applied to these clocks. AC-coupling
and then DC-shifting the CRxS phases will produce the CRxB
phases.
The final storage electrode of each readout register is connected
separately to CRLAST. CRLAST should be clocked in phase with
CR1.
All CR clocks operate with 50% duty cycle.
Unlike CR1 and CR2, the CRLAST pin is connected to only two
CCD gates, one for each of the two CCD shift registers on each
side. Consequently, the CRLAST capacitance is much smaller
than the CR1 or CR2 capacitance. To prevent CRLAST from
switching much faster than CR1 and CR2, we recommend that a
100Ωresistor be connected in series with CRLAST. The
CRLAST clock should preferably have a slower rise and fall time
than CR1 and CR2.
Additional details on driving the sensor are provided on Figure 7.
Output
The signal charge packets from the readout shift registers are
transferred serially from the last readout gate (CRLAST), over
the set gate (VSET), to a floating sense node diffusion. The set
gate isolates the sense node diffusion from the last readout gate
and the rest of the readout shift register. As signal charge accu-
mulates on the floating node diffusion, the potential of this diffu-
sion decreases. The floating node diffusion is connected to the
input of a 2.5-stage low-noise amplifier, producing an output
signal voltage on the amplifier output (OSn). The floating diffu-
sion is cleared of signal charge by the reset gate (RST) in prepa-
ration for the next signal charge packet. The voltage level of the
floating diffusion after each reset is determined by the output re-
set drain voltage (VOD). AC coupling the output is recom-
mended to eliminate the DC offset.
Each of the output signals (OSn) requires an off-chip load draw-
ing approximately 8mA of load current. If the sensor is running at
greater than 35MHz data rate, or if the load capacitance (CLOAD)
is greater than 10pF, larger load current (up to the 18mA limit)
may be required. As the load current increases, the amplifier
bandwidth increases. The amplifier can also drive larger capaci-
tive loads when the load current is larger. We recommend how-
ever that just enough bandwidth be used since larger bandwidth
also results in increased noise.
If an off-chip current load is not available, each of the amplifier
outputs (OSn) can be connected to a 1.2kΩload resistor. The
use of a passive (resistive) load reduces the amplifier gain, re-
sulting in lower responsivity and saturation output signal.
The variations in charge conversion efficiency among the vari-
ous outputs of the sensor, along with component variations in
the drive electronics, result in output gain mismatch. To match
outputs, we recommend that the camera electronics incorpo-
rate gain correction.
The isolation pixels should not be used for calibration or
detection.
03-036-00183-07 DALSA Corp.: Phone: 519-886-6000 Fax: 519-886-8023 3
www.dalsa.com DALSA EUROPE: Phone: +49-8142-46770 Fax: +49-8142-467746 ISO 9001
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