Maxim Integrated MAXQ7667 - Manual (Page 243)

14-11 _________________________________________________________________________________________________________
MAXQ7667 User’s Guide
14.5.3 Unipolar/Bipolar
The MAXQ7667 ADC produces a digital output that corresponds to the differential analog input voltage as long as the differential ana-
log inputs are within the specified range. The analog inputs are configured for differential conversion when the SARDIF (SARC.8) con-
trol bit is set. When performing differential conversions, the control bit SARBIP (SARC.7) selects between unipolar and bipolar opera-
tion modes. Unipolar mode sets the differential input range from 0 to REF. A negative differential analog input in unipolar mode caus-
es the digital output code to be zero. Selecting bipolar mode sets the differential input range to -REF/2 to +REF/2. The digital output
code is straight binary in unipolar mode and two’s complement in bipolar mode.
In single-ended mode (SARDIF set to 0), the MAXQ7667 ADC analog inputs are internally referenced to AGND. Selecting unipolar
mode sets the full-scale input range to 0 to REF. Bipolar mode sets the full-scale input range to 0 to REF/2. As above, the digital out-
put code is straight binary in unipolar mode and two’s complement in bipolar mode.
Figure 14-3. Equivalent Input Circuit (Hold/Conversion Mode)
CONTROL
LOGIC
CAPACITIVE
DAC
AGND
AIN+
AIN-
CIN+
CIN-
RIN+
RIN-
COMP
AVDD
Figure 14-2. Equivalent Input Circuit (Track/Acquisition Mode)
CONTROL
LOGIC
CAPACITIVE
DAC
AGND
AIN+
AIN-
CIN+
AVDD
CIN-
RIN+
RIN-
COMP