Specifications

3.2 MECHANISM OF THE CCD ELECTRICAL
CHARGE TRANSMISSION
The TMC-7 uses a 4-phase drive method CCD. For
simplicity, a 2-phase drive method CCD is explained
below.
Figure 1 shows an example of the changes which can
occur in potential wells in successive time intervals.
At t1, the electrode voltages are fH1>fH2, so the
potential wells are deeper toward the electrode at the
higher voltage fH1. An electrical charge accumulates
in these deep wells.
At t2, the clock voltages fH1 and fH2 are reversed;
now the wells toward the electrode at voltage fH2
become deeper while those toward the electrode at
fH1 become shallower. So the wells at fH2 are deeper
than those at fH1 and the signal charge flows toward
the deeper wells.
At t3, the electrode voltages have not changed
because of t2, so the signal charge flows into the wells
toward the electrode at fH2; one transmission of elec-
trical charge is completed. This action is repeated over
and over to execute the horizontal transmissions.
Vertical transfer
The vertical shift register transfers charges using a
four-phase drive mode. Figure 2 shows an example of
the changes which can occur in potential wells in suc-
cessive time intervals. At tO, the electrode voltages are
(V1 = V2)>(V3 = V4), so the potential wells are deeper
toward the electrode at the higher voltages V1 and V2.
Charges accumulate in these deep wells.
At t1, the electrode voltages are (V1 = V2 = V3)>(V4),
so the charges accumulate in the wells toward the
electrode at V1, V2 and V3.
At t2, the electrode voltages are (V2 = V3)>(V4 = V1),
so the charges accumulate in the wells toward the
electrode at V2 and V3. Electrode voltage states at t3
and after are shown below.
t3(V2 = V3 = V4)>(V1)
t4(V3 = V4)>(V1 = V2)
t5(V4>(V1 = V2 = V3)
t6(V4 = V1)>(V2 = V3)
t7(V4 = V1 = V2)>(V3)
t8(V1 = V2)>(V3 = V4) (Initial state)
These operations are repeated to execute the vertical
transfer.
t1
t2
t3
time
potential profile
transfer direction
Operating Pulse Waveforms (ø1, ø2 or øH1, øH2)
(minus) shows lower
impurity concentration
potential profile
P - sub
ø2
ø1
t
N-
N
N- N N- N N- N N-
N, N- * : N type impurity
* -
V1
V0
ø2
V1
V0
ø1
V1 > VO
t1 t2 t3
transfer direction
V1
V2
V3
V4
t0
t1
t2
t3
t4
t5
t6
t7
t8
4 Phase CCD Drive
3
Figure 1
Figure 2