鈥?/div>
adjustable clock frequency increases or decreases
time required to change diode impedance
STANDARD PACKAGING
鈥?10 pin PLID
廬
CIRCUIT DESCRIPTION
The GT560 is a low voltage transconductance block which
can be used as an electronic volume control. The
transconductance element consists of two diodes back-to-
back, whose impedance is varied by changing the amount of
current through the diodes.
The impedance of the diodes is controlled by digital circuitry
which consists of:
鈥?an oscillator with an external capacitor,
C
T
, to set the
ramp frequency 茠
c,
5 x 10
-7
茠
鈮?/div>
c
C
T
鈥?logic interface, which senses the volume up-down controls
鈥?a digital / analog converter
鈥?the control logic/debounce logic
鈥?synchronous up-down counter
To increase or decrease the GT560 impedance, the switching
mechanism can be touch sensitive contacts or a mechanical
switch. In either configuration, the switches are connected
from pin 8 to V
CC
and pin 9 to V
CC
. Any resistance (30 M鈩?typ.),
from pin 8 or 9 to V
CC
will activate the GT560 control circuitry
and the device will change impedance levels.
鈥?Chip (79 x 60 mils)
LOGIC SUPPLY
(MEMORY)
ANALOG
SUPPLY
6
MODE
CONTROL
UP
CONTROL
DOWN
CONTROL
7
8
9
LOGIC
INPUT
INTERFACE
CONTROL
LOGIC
1
DIGITAL
TO
ANALOG
4
N/C
CT
10
CLOCK
OSCILLATOR
CURRENT
CONTROLLED
RESISTANCE
LINEAR
TO LOG
CONVERTER
3
2
5
RA
RB
GND
BLOCK DIAGRAM
Revision Date: January 2001
Document No. 510 - 64 - 03
GENNUM CORPORATION P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3 tel. +1 (905) 632-2996
Web Site: www.gennum.com E-mail: hipinfo@gennum.com
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