TC826 Datasheet, PDF (7/18 Pages) TelCom Semiconductor, Inc – A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT

For a constant V_IN:
EQUATION 3-2:
V_IN = V_R
T_RI
T_SI
The dual slope converter accuracy is unrelated to the
integrating resistor and capacitor values, as long as
they are stable during a measurement cycle. An inher-
ent benefit is noise immunity. Noise spikes are inte-
grated or averaged to zero during the integration
periods. Integrating ADCs are immune to the large con-
version errors that plague successive approximation
converters in high noise environments. Interfering sig-
nals with frequency components at multiples of the
averaging period will be attenuated (Figure 3-2).
The TC826 converter improves the conventional dual
slope conversion technique by incorporating an auto-
zero phase. This phase eliminates zero scale offset
errors and drift. A potentiometer is not required to
obtain a zero output for zero input.
TC826
FIGURE 3-2:
NORMAL MODE
REJECTION OF DUAL
SLOPE CONVERTER
30
T = Measurement
Period
20
10
0
0.1/T
1/T
Input Frequency
10/T
© 2002 Microchip Technology Inc.
DS21477B-page 7