Absdute
Maximum
Ratings
\
current), every
100R
will cause
a
1
%
Increase
In
con trel scale
error. As the times are increased,
this error will decrease in
d~rect
proportion.
The
voltage applied to the
sustain level control input will
directly determine the sustain
voltage of the output envelope
(minus
the sustain final voltage
error). Voltages greater than
the
threshold voltage will cause
the
envelope to ramp
up
to
this
higher voltage
when
the
peak
threshold is reached. The rate
a?
which thls occurs
will
be
equal
to the fastest attack rate.
Since all four control inputs
are connected
only
to the
bases
of
NPN
transistors, the control
input pins
of
tracking units may
be simply tied together. There-
fore,
in
the
case
of
the time
control inputs, only one
atten-
uator network is required to
controy the same parameter in
a
multiple
chip
system.
Selection
of
RX
and
CX
As
is
shown
in
the envelope
equations, the
Rc
time constant
of
the attack,
decay
and
release
curves is given
by
RXCX
times
The
exworrential multiplier.
exp(-vC/vT). ~ractidal circuit
limitations
determ~ne
RX
and
the
multipller, from which
CX
can
then be calculated. The peak
capacitor charging and discharg-
ing
currents
is
given
by
{VZ/
a
X)~XP{VCA/VT).
(VCSIRX)
explVc~IV~1,
and
(VP/R
x)exp
IVCR/VT) for the attack, decay,
and
release phases respectively.
For the best
scale
accuracv and
tracking
at
the shortest times.
these
currents should be kept
less
than
100
FA,
and in
all
cases
they
should not
be
allowed
to exceed
300
PA.
Thls sets the
minimum
value for
RX
at
24K.
Larger
values
of
RX
will allow
positive
time control voltages to
be used.
However,
as
can
also
be
Voltage Between
VCC
and
VEE
Pins
a
24V
Voltage Between VCC
and
Ground Pins
+T8V
Voltage Between
VEE
and Ground Pins
-6.OV
Current Into
VEE
Pin
+50mA
Voltage Between Control and Ground Pins
L6.W
Voltage
to Gate and Trigger lnput
Pin5
VEE
to
VCC
Storage Temperature Range
-55"~
to
+150O~
Operating Temperature Range
-25"~
to
+75"~
seen from the envelope
equa-
tions, the sustainlfinal voltage
error, the asymptote error, and
the
control
voltage feedthrough
are
aBI
affected
by
Rx.
A
prac-
tical
maximum
of
240K
is
recommended
for
RX
when the
internal
buffer
IS
used and 1
M
if
an
external
FET
buffer
is
used,
Trimming
the
EnvelopeTimes
The
RC
time constants of the
output
envelope
will typically
track
to
within
+
15%
from
unit
to unit,
even
at the longest time
settings.
Sf
better tracking
is
required, the best method for
trimming the
tlme constants
is
to simply adjust
RX
with
a
trimming potentiometer.
Output
Drive
Capability
The buffer output can sink at
least
400
MA
and can source
up
to
1
OmA.
but with considerable
degradation in performance. An
output load no less than
20K
TO
ground
is
recommended.
The buffer has
a
somewhat
high output impedance,
As
a
result
of
this,
small steps
(50mV)
appear in the output waveform
at the phase transitions,
due
to
the
sudden change in drive
the
output
must
provide to
Rx.
The
largest step is at the beginning
of
the
envelope
and
is
given by
(RQ/Rx)VZ.
It
may
be
de-
creased
by
increasing
Rx,
lower-
ing
RQ,
or
using
an5external buf-
fer with
a
low output impedance.
RQ
may
be
lowered
by
adding
a
resistor from the output pin
to
VEE.
However,
every
IrnA
of
current
drawn from the output
pin
may
irlcrease the
buffer
input current
as
much as
5-6
nA
with consequent degradation
in
performance.
Envelope
Equations
Release
Curve
EF
=VOS
+
IB1RX
-
IB2RX/1+e
Attack/Decay/Release
Asymptote
Error
EA
=
VQS
+
(67
RX
-
IsrRx
e
V~A
=
Attack Control Voltage
V~D
=
Decay Control Voltage
VCR
Release Control Voltage
Vcs
=
Sustain Control Voltage
VOS
=
Op
Amp
Offset
IB1
=
Op
Amp
lnput Current
tg2
=
Buffer lnput Current
VZ
=
Attack Asymptote Voltage
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