AD590
Figure 18. Matrix 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. T he resulting circuit can select one of eighty
sensors over only 18 wires with a 7-bit binary word. T he inhibit
input on the multiplexer turns all sensors off for minimum
dissipation while idling.
Figure 19. 8-Channel Multiplexer
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. T he 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.
REV. B
–9–
ADI [ ADI ]
