8XC196MD
A TO D CHARACTERISTICS
The sample and conversion time of the AD convert-
er in the 8-bit or 10-bit modes is programmed by
loading a byte into the AD
TIME Special Function
Register This allows optimizing the AD operation
for specific applications The AD
TIME register is
functional for all possible values but the accuracy of
the AD converter is only guaranteed for the times
specificed in the operating conditions table
The value loaded into AD
TIME bits 5 6 7 deter-
mines the sample time TSAM and is calculated us-
ing the following formula
SAM e
(TSAM c FOSC) b 2
8
TSAM e Sample time ms
FOSC e Processor frequency MHz
SAM e Value loaded into AD
TIME
bits 5 6 7
SAM must be in the range 1 through 7
The value loaded into AD
TIME bits 0 – 5 deter-
mines the conversion time TCONV and is calculated
using the following formula
CONV e
(TCONV c FOSC) b 3
2B
b
1
TCONV e Conversion time ms
FOSC e Processor frequency MHz
B e 8 for 8-bit conversion
B e 10 for 10-bit conversion
CONV e Value loaded into AD
TIME
bits 0 – 5
CONV must be in the range 2 through 31
The converter is ratiometric so absolute accuracy is
dependent on the accuracy and stability of VREF
VREF must be close to VCC since it supplies both the
resistor ladder and the analog portion of the convert-
er and input port pins There is also an AD
TEST
SFR that allows for conversion on ANGND and
VREF as well as adjusting the zero offset The abso-
lute error listed is WITHOUT doing any adjustments
AD CONVERTER SPECIFICATION
The specifications given assume adherence to the
operating conditions section of this data sheet Test-
ing is performed with VREF e 512V and 160 MHz
operating frequency After a conversion is started
the device is placed in the IDLE mode until the con-
version is complete
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