Antiblooming is always present when biases fall within the
specified operating conditions. By adjusting VSTOR how-
ever, the user has the added flexibility of selecting the anti-
blooming level (the signal level beyond which additional
signal charges are drained away). A higher VSTOR bias re-
sults in a higher antiblooming level.
Transfer
The TCK clock controls the transfer of electrons from the
storage well into two discrete readout registers for alter-
nating 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
packetstothetwohigh-speedlow-noiseoutputamplifiers.
The two readout registers are pseudo-2-phase buried-
channel CCD shift registers. The CR1x and CR2x phases
are complements of each other. Each of these two phases
hasastorage(CRxS)andabarrier(CRxB)gate.Thestorage
and barrier gates of each phase are clocked in phase (i.e.,
CR1Sis clockedinphase withCR1B,andCR2S isclockedin
phasewith CR2B).Theonlydifferencebetweenthestorage
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 con-
nected 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
twoCCDgates,oneforeachofthetwoCCDshiftregisters
on each side. Consequently, the CRLAST capacitance is
muchsmaller thantheCR1or CR2capacitance.Toprevent
CRLASTfromswitchingmuchfasterthanCR1andCR2,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.
Additionaldetailsondrivingthe sensorareprovided onFig-
ure 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
nodediffusion.Thesetgateisolatesthesensenodediffusion
from the last readout gate and the rest of the readout shift
register. As signal charge accumulates on the floating node
diffusion,thepotentialofthisdiffusiondecreases.Thefloat-
ing 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 diffusion is cleared
of signal charge by the reset gate (RST) in preparation for
the next signal charge packet. The voltage level of the float-
ingdiffusionaftereachresetisdeterminedbytheoutputre-
set drain voltage (VOD). AC coupling the output is
recommended to eliminate the DC offset.
Each of the output signals (OSn) requires an off-chip load
drawingapproximately8mAofloadcurrent.If the sensor is
running at greater than 35MHz data rate, or if the load ca-
pacitance (CLOAD) is greater than 10pF, larger load current
(upto the 18mAlimit)mayberequired. As theloadcurrent
increases, the amplifier bandwidth increases. The amplifier
can also drive larger capacitive loads when the load current
is larger. We recommend however that just enough band-
width be used since larger bandwidth also results in in-
creased noise.
If an off-chip current load is not available, each of the ampli-
fier outputs (OSn) can be connected to a 1.2kΩload resis-
tor. The use of a passive (resistive) load reduces the
amplifiergain,resultingin lower responsivity and saturation
output signal.
The variations in charge conversion efficiency among the
various outputs of the sensor, along with component varia-
tions in the drive electronics, result in output gain mis-
match. To match outputs, we recommend that the camera
electronics incorporate a gain correction of up to 15%.
03-36-00134-05 DALSA INC.: 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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