AD7927 Analog Devices, AD7927 Datasheet - Page 13

• Manufacturer Part Number: AD7927
• Description: 8-Channel, 200 kSPS, 12-Bit ADC with Sequencer in 20-Lead TSSOP
• Manufacturer: Analog Devices

Specifications of AD7927

• Resolution (bits): 12bit
• # Chan: 8
• Sample Rate: 200kSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni (Vref) x 2
• Adc Architecture: SAR
• Pkg Type: SOP

Data Sheet
SEQUENCER OPERATION
The configuration of the SEQ and SHADOW bits in the control register allows the user to select a particular mode of operation of the
sequencer function. Table 9 outlines the four modes of operation of the sequencer.
Table 9. Sequence Selection
SEQ
0
0
1
1
SHADOW
0
1
0
1
Sequence Type
This configuration means that the sequence function is not used. The analog input channel selected for each
individual conversion is determined by the contents of the channel address bits, ADD0 through ADD2, in each
prior write operation. This mode of operation reflects the traditional operation of a multichannel ADC, without
the sequencer function being used, where each write to the AD7927 selects the next channel for conversion (see
Figure 11).
This configuration selects the shadow register for programming. The following write operation loads the contents of
the shadow register. This programs the sequence of channels converted on continuously with each successive valid
CS falling edge (see the Shadow Register section, Table 10, and Figure 12). The channels selected need not be
consecutive.
If the SEQ and SHADOW bits are set in this way, the sequence function is not interrupted upon completion of
the WRITE operation. This allows other bits in the control register to be altered between conversions while in a
sequence, without terminating the cycle.
This configuration is used in conjunction with the channel address bits, ADD2 to ADD0, to program continuous
conversions on a consecutive sequence of channels from Channel 0 to a selected final channel as determined by
the channel address bits in the control register (see Figure 13).
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AD7927