ISO-CMOS
Functional Description
The MT8806 is an analog switch matrix with an array
size of 8 x 4. The switch array is arranged such that
there are 8 columns by 4 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 32
bit write only RAM in which the bits are selected by
the address inputs (AY0-AY2, AX0 & AX1). Data is
presented to the memory on the DATA input. Data is
asynchronously written into memory whenever both
the CS (Chip Select) and the STROBE inputs are
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 regardless of whether CS is high
or low. Two voltage reference pins (V
SS
and V
EE
)
are provided for the MT8806 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.
MT8806
Address Decode
The five address inputs along with the STROBE and
CS (Chip Select) inputs 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 and CS must go high 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.
3-11
MITEL [ MITEL NETWORKS CORPORATION ]
