ISO-CMOS
Functional Description
The MT8815 is an analog switch matrix with an array
size of 8×12. The switch array is arranged such that
there are 8 columns by 12 rows. The columns are
referred to as the Y inputs/outputs and the rows are
the X inputs/outputs. The crosspoint analog switch
array will interconnect any X I/O with any Y I/O when
turned on and provide a high degree of isolation
when turned off. The control memory consists of a 96
bit write only RAM in which the bits are selected by
the address inputs (AY0-AY2, AX0-AX3). Data is
presented to the memory on the DATA input. Data is
asynchronously written into memory whenever the
STROBE input is high and is latched on the falling
edge of STROBE. A logical “1” written into a
memory cell turns the corresponding crosspoint
switch on and a logical “0” turns the crosspoint off.
Only the crosspoint switches corresponding to the
addressed memory location are altered when data is
written into memory. The remaining switches retain
their previous states. Any combination of X and Y
inputs/outputs can be interconnected by establishing
appropriate patterns in the control memory. A logical
“1” on the RESET input will asynchronously return all
memory locations to logical “0” turning off all
crosspoint switches. Two voltage reference pins
(V
SS
and V
EE
) are provided for the MT8815 to
enable switching of negative analog signals. The
range for digital signals is from V
DD
to V
SS
while the
range for analog signals is from V
DD
to V
EE
. V
SS
and V
EE
pins can be tied together if a single voltage
reference is needed.
MT8815
Address Decode
The seven address inputs along with the STROBE
are logically ANDed to form an enable signal for the
resettable transparent latches. The DATA input is
buffered and is used as the input to all latches. To
write to a location, RESET must be low while the
address and data are set up. Then the STROBE
input is set high and then low causing the data to be
latched. The data can be changed while STROBE is
high, however, the corresponding switch will turn on
and off in accordance with the DATA input. DATA
must be stable on the falling edge of STROBE in
order for correct data to be written to the latch.
3-41
MITEL [ MITEL NETWORKS CORPORATION ]
