Datasheet

Software-Controlled Switches (SoftConfig)
2-4 ADSP-BF609 EZ-KIT Lite Evaluation System Manual
Figure 2-2 shows two individual FET switches (Pericom PI3A125CEX)
with reference designators UA and UB. Net names
ENABLE_A and ENABLE_
B
control UA and UB. The default FET switch enable settings in this
example are controlled by resistors RA and RB which pull the enable pin 1
of UA and UB to ground (low). In a real example, these enable signals are
controlled by the Microchip IO expander. The default pull-down resistors
connects the signals EXAMPLE_SIGNAL_A and EXAMPLE_SIGNAL_B and also
connects signals EXAMPLE_SIGNAL_C and EXAMPLE_SIGNAL_D. To disconnect
EXAMPLE_SIGNAL_A from EXAMPLE_SIGNAL_B, the Microchip IO expander is
used to change ENABLE_A to a logic 1 through software that interfaces with
the Microchip. The same procedure for ENABLE_B would disconnect
EXAMPLE_SIGNAL_C from EXAMPLE_SIGNAL_D.
Figure 2-3 shows the equivalent circuit to Figure 2-2 but utilizes mechan-
ical switches that are in the same package. Notice the default is shown by
black boxes located closer to the ON label of the switches. In order to dis-
connect these switches, physically move the switch to the
OFF position.
Figure 2-2. Example of Individual FET Switches