Datasheet

AD590
REV. B
–9–
Figure 18. Matrix Multiplexer
Figure 19. 8-Channel Multiplexer
CMOS Analog Multiplexers can also be used to switch AD590
current. Due to the AD590’s current mode, the resistance of
such switches is unimportant as long as 4 V is maintained across
the transducer. Figure 18 shows a circuit which combines the
principal demonstrated in Figure 17 with an 8-channel CMOS
Multiplexer. The resulting circuit can select one of eighty
sensors over only 18 wires with a 7-bit binary word. The inhibit
input on the multiplexer turns all sensors off for minimum
dissipation while idling.
Figure 19 demonstrates a method of multiplexing the AD590 in
the two-trim mode (Figure 7). Additional AD590s and their
associated resistors can be added to multiplex up to 8 channels
of ±0.5°C absolute accuracy over the temperature range of
–55°C to +125°C. The high temperature restriction of +125°C
is due to the output range of the op amps; output to +150°C
can be achieved by using a +20 V supply for the op amp.