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© 2010 Microchip Technology Inc. Preliminary DS39737A-page 49-17
Section 49. 10-Bit ADC with 4 Simultaneous Conversions
10-Bit ADC with
4 Simultaneous
Conversions
49
49.3.6 Multi-Channel Sample Conversion Sequence
Multi-channel A/D Converters typically convert each input channel sequentially using an input
multiplexer. Simultaneously sampling multiple signals ensures that the snapshot of the analog
inputs occurs at precisely the same time for all inputs, as shown in Figure 49-7.
Certain applications require simultaneous sampling, especially when phase information exists
between different channels. Sequential sampling takes a snapshot of each analog input, just
before conversion starts on that input, as shown in Figure 49-7. The sampling of multiple inputs
is not correlated. For example, motor control and power monitoring require voltage and current
measurements and the phase angle between them.
Figure 49-7: Simultaneous and Sequential Sampling
Figure 49-8 and Figure 49-9 illustrate that the ADC module supports simultaneous sampling,
using two S&H or four S&H channels to sample the inputs at the same instant, and then performs
the conversion for each channel sequentially.
The Simultaneous Sampling mode is selected by setting Simultaneous Sampling bit (SIMSAM)
in the ADC Control Register 1 (ADxCON1<3>). By default, the channels are sampled and
converted sequentially. Table 49-4 lists the options selected by a specific bit configuration. The
CHPS<1:0> bits determine the channels to be sampled, either sequentially or simultaneously.
Table 49-4: Start of Sampling Selection
SIMSAM Sampling Mode
0 Sequential Sampling
1 Simultaneous Sampling
AN0
AN1
AN2
AN3
Simultaneous
Sampling
Sequential
Sampling
Protego_Release_01_05-Related-OEM-Documentation-PIC24FJ32MC10X-Reference_Manual-Section49-10-Bit_ADC_with_4_Simultaneous_Conversions.pdf