Cirrus Logic AN75 - Manual (Page 3)

AN75
AN75REV2 3
Figure 5 illustrates the CS5525/CS5526 configured
to interface to a bridge transducer. The bridge is ex-
cited with +5 V. The voltage reference for the A/D
is derived from the +5 V which excites the bridge
to set up a ratiometric measurement configuration.
A ALD4201 quad analog switch is used to select
between the differential bridge signal and a ther-
mistor temperature sensor which is being used to
measure the bridge temperature. The CS5525/CS5526 has four digital outputs that
can be used to control as many as 16 analog switch-
es with the use of either the 74HC137 or 74HC237
1-of-8 Decoder/Multiplexers. The main difference
between the two chips is that the 74HC137 has ac-
tive low outputs; the 74HC237 has active high out-
puts. Figure 6 illustrates how the CS5525/CS5526
digital outputs (D0-D3) can be used to derive 16
separate control lines using a pair of 74HC237s.
Figure 4. CS5525/CS5526 Controls the low-voltage ALD4201 analog switch.
Figure 5. CS5525/CS5526 Controls the low-voltage ALD4201 analog switch.