AD7792/AD7793
Rev. B | Page 16 of 32
Table 15. Operating Modes
MD2
MD1
MD0
Mode
0
Continuous Conversion Mode (Default).
In continuous conversion mode, the ADC continuously performs conversions and places the result in the data
register. RDY goes low when a conversion is complete. The user can read these conversions by placing the device in
continuous read mode, whereby the conversions are automatically placed on the DOUT line when SCLK pulses are
applied. Alternatively, the user can instruct the ADC to output the conversion by writing to the communications
register. After power-on, a channel change, or a write to the mode, configuration, or IO registers, the first conversion
is available after a period of 2/fADC. Subsequent conversions are available at a frequency of fADC.
0
1
Single Conversion Mode.
When single conversion mode is selected, the ADC powers up and performs a single conversion. The oscillator
requires 1 ms to power up and settle. The ADC then performs the conversion, which takes a time of 2/fADC. The
conversion result is placed in the data register, RDY goes low, and the ADC returns to power-down mode. The
conversion remains in the data register, and RDY remains active low until the data is read or another conversion is
performed.
0
1
0
Idle Mode.
In idle mode, the ADC filter and modulator are held in a reset state, although the modulator clocks are still provided.
0
1
Power-Down Mode.
In power-down mode, all the AD7792/AD7793 circuitry is powered down, including the current sources, burnout
currents, bias voltage generator, and CLKOUT circuitry.
1
0
Internal Zero-Scale Calibration.
An internal short is automatically connected to the enabled channel. A calibration takes 2 conversion cycles to
complete. RDY goes high when the calibration is initiated and returns low when the calibration is complete. The
ADC is placed in idle mode following a calibration. The measured offset coefficient is placed in the offset register of
the selected channel.
1
0
1
Internal Full-Scale Calibration.
A full-scale input voltage is automatically connected to the selected analog input for this calibration.
When the gain equals 1, a calibration takes 2 conversion cycles to complete. For higher gains, 4 conversion cycles
are required to perform the full-scale calibration.
RDY goes high when the calibration is initiated and returns low when the calibration is complete. The ADC is placed
in idle mode following a calibration. The measured full-scale coefficient is placed in the full-scale register of the
selected channel.
Internal full-scale calibrations cannot be performed when the gain equals 128. With this gain setting, a system full-
scale calibration can be performed.
A full-scale calibration is required each time the gain of a channel is changed to minimize the full-scale error.
1
0
System Zero-Scale Calibration.
User should connect the system zero-scale input to the channel input pins as selected by the CH2 to CH0 bits. A
system offset calibration takes 2 conversion cycles to complete. RDY goes high when the calibration is initiated and
returns low when the calibration is complete. The ADC is placed in idle mode following a calibration. The measured
offset coefficient is placed in the offset register of the selected channel.
1
System Full-Scale Calibration.
User should connect the system full-scale input to the channel input pins as selected by the CH2 to CH0 bits.
A calibration takes 2 conversion cycles to complete. RDY goes high when the calibration is initiated and returns low
when the calibration is complete. The ADC is placed in idle mode following a calibration. The measured full-scale
coefficient is placed in the full-scale register of the selected channel.
A full-scale calibration is required each time the gain of a channel is changed.
Table 16. Update Rates Available
FS3
FS2
FS1
FS0
fADC (Hz)
tSETTLE (ms)
Rejection @ 50 Hz/60 Hz (Internal Clock)
0
x
0
1
470
4
0
1
0
242
8
0
1
123
16
0
1
0
62
32
0
1
0
1
50
40
0
1
0
39
48
0
1
33.2
60
1
0
19.6
101
90 dB (60 Hz only)