Datasheet

© 2008 Microchip Technology Inc. DS21455D-page 15
TC7106/A/TC7107/A
In some applications, a scale factor other than unity
may exist between a transducer output voltage and the
required digital reading. Assume, for example, a
pressure transducer output is 400 mV for 2000 lb/in
2
.
Rather than dividing the input voltage by two, the
reference voltage should be set to 200 mV. This
permits the transducer input to be used directly.
The differential reference can also be used when a
digital zero reading is required when V
IN
is not equal to
zero. This is common in temperature measuring
instrumentation. A compensating offset voltage can be
applied between analog common and V
IN
-. The
transducer output is connected between V
IN
+ and
analog common.
The internal voltage reference potential available at
analog common will normally be used to supply the
converter’s reference. This potential is stable
whenever the supply potential is greater than
approximately 7V. In applications where an externally
generated reference voltage is desired, refer to
Figure 7-1.
FIGURE 7-1: External Reference.
TC7106A
TC7107A
6.8V
Zener
I
Z
V+
V+
V+
1.2V
Ref
Common
TC7106A
TC7107A
6.8 k Ω
20 k Ω
V
REF
+
V
REF
-
V
REF
+
V
REF
-
(a) (b)
V+