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11
11-41
32170/32174 Group User's Manual (Rev. 2.1)
11.3 Functional Description of A-D Converters
11.3.1 How to Find Along Input Voltages
The A-D converters use a 10-bit successive approximation method, and find the actual analog input
voltage from the value (digital quantity) obtained through execution of A-D conversion by
performing the following calculation.
The A-D converters are a 10-bit converter, providing a resolution of 1,024 discrete voltage levels.
Because the reference voltage for the A-D converter is the voltage applied to the VREF pin, make
sure an exact and stable constant-voltage power supply is connected to VREF. Also, make sure the
analog circuit power supply and ground (AVCC, AVSS) are separated from those of the digital
circuit, with sufficient noise prevention measures incorporated.
For details about the conversion accuracy, refer to Section 11.3.5, "Accuracy of A-D Conversion."
Analog input voltage [V] =
Figure 11.3.1 Outline Block Diagram of the Successive Approximation-type A-D Converter Unit
A-D conversion result
× VREF input voltage [V]
1024
A-D CONVERTERS
11.3 Functional Description of A-D Converters
ADiIN0
ADiIN1
ADiIN2
ADiIN3
ADiIN4
ADiIN5
ADiIN6
ADiIN7
Selector
AVSSi
VREFi
10-bit A-Di successive
approximation register
(ADiSAR)
10-bit A-Di data register
A-Di comparate
data register
A-D control circuit
10-bit A-D converter
Comparator
ADiIN8
ADiIN9
ADiIN10
ADiIN11
ADiIN12
ADiIN13
ADiIN14
ADiIN15
ADiCMP
ADiDT0-15
Successive approximation-type
A-D converter unit
AVCCi
Vref
VIN
i=0, 1