Datasheet

 
 
SBAS323G − JUNE 2004 − REVISED OCTOBER 2007
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26
OVERVIEW
The MSC1211/12/13/14 ADC structure is shown in
Figure 12. The figure lists the components that make up
the ADC, along with the corresponding special function
register (SFR) associated with each component.
ADC INPUT MULTIPLEXER
The input multiplexer provides for any combination of
differential inputs to be selected as the input channel, as
shown in Figure 13. For example, if AIN0 is selected as the
positive differential input channel, then any other channel
can be selected as the negative differential input channel.
With this method, it is possible to have up to eight fully
differential input channels with common connections
between them. It is also possible to switch the polarity of
the differential input pair to negate any offset voltages. In
addition, current sources are supplied that will source or
sink current to detect open or short circuits on the pins.
TEMPERATURE SENSOR
On-chip diodes provide temperature sensing capability.
When the configuration register for the input MUX is set to
all 1s, the diodes are connected to the inputs of the ADC.
All other channels are open.
BURNOUT DETECT
When the Burnout Detect (BOD) bit is set in the ADC
control configuration register (ADCON0 DCh), two current
sources are enabled. The current source on the positive
input channel sources approximately 2µA of current. The
current source on the negative input channel sinks
approximately 2µA. The current sources allow for the
detection of an open circuit (full-scale reading) or short
circuit (small differential reading) on the selected input
differential pair. The buffer should be on for sensor burnout
detection.
Σ
Σ
X
Input
Multiplexer
Temperature
Sensor
Buffer PGA
Sample
and Hold
ADMUXD7h
REFOUT/
REFIN+
REFIN
−
REFOUT/
REFIN+
f
MOD
REFIN
−
AIN5
AIN6
AIN7
AINCOM
ADCON1DDh
ADCON2DEh
ADCON3DFh
OCR GCR ADRES
SUMR
D3h
D2h D1h D6h D5h D4h DBh DAh D9h
E5h E4h E3h E2h
Offset
Calibration
Register
ADC0N0DCh ACLKF6h
SSCON
E1h
ODACE6h
Offset
DAC
∆Σ
ADC
Modulator
FAST
SINC2
SINC3
AUTO
ADC
Result Register
Σ
Summation
Block
V
IN
AIN2
AIN3
AIN4
AIN0
AIN1
f
SAMP
f
DATA
Gain
Calibration
Register
Burnout
Detect
AV
DD
In+
AGND
In
−
Burnout
Detect
AIPOL.5A4h
AISTAT.5A7h
AIE.5A6h
AIPOL.6A4h
AISTAT.6A7h
AIE.6A6h
Figure 12. MSC1211/12/13/14 ADC Structure