ADG2108_15 Datasheet, PDF (18/28 Pages) Analog Devices – Switch Array with Dual/Single Supplies

ADG2108
THEORY OF OPERATION
The ADG2108 is an analog cross point switch with an array size
of 8 × 10. The 10 rows are referred to as the X input/output lines,
and the eight columns are referred to as the Y input/output
lines. The device is fully flexible in that it connects any X line or
number of X lines with any Y line when turned on. Similarly, it
connects any X line with any number of Y lines when turned on.
Control of the ADG2108 is carried out via an I²C interface.
The device can be operated from single supplies of up to 13.2 V
or from dual ±5 V supplies. The ADG2108 has many attractive
features, such as the ability to reset all the switches, the ability to
update many switches at the same time, and the option of reading
back the status of any switch. All of these features are described
in more detail here in the Theory of Operation section.
RESET/POWER-ON RESET
The ADG2108 offers the ability to reset all of the 80 switches to
the off state. This is done through the RESET pin. When the
RESET pin is low, all switches are open (off), and appropriate
registers are cleared. Note that the ADG2108 also has a power-
on reset block. This ensures that all switches are in the off
condition at power-up of the device. In addition, all internal
registers are filled with 0s and remain so until a valid write to
the ADG2108 takes place.
Data Sheet
LOAD SWITCH (LDSW)
LDSW is an active high command that allows a number of
switches to be simultaneously updated. This is useful in
applications where it is important to have synchronous
transmission of signals. There are two LDSW modes: the
transparent mode and the latched mode.
Transparent Mode
In this mode, the switch position changes after the new word is
written into the input shift register. LDSW is set to 1.
Latched Mode
In this mode, the switch positions are not updated at the same
time that the input registers are written to. This is achieved by
setting LDSW to 0 for each word (apart from the last word)
written to the device. Then, setting LDSW to 1 for the last word
allows all of the switches in that sequence to be simultaneously
updated.
READBACK
Readback of the switch array conditions is also offered when in
standard mode and fast mode. Readback enables the user to
check the status of the switches of the ADG2108. This is very
useful when debugging a system.
Rev. B | Page 18 of 28