ata6616 ATMEL Corporation, ata6616 Datasheet - Page 227

• Manufacturer Part Number: ata6616
• Description: Microcontroller With Lin Transceiver, 5v Regulator And Watchdog
• Manufacturer: ATMEL Corporation

4.18.8
4.18.8.1
4.18.8.2
4.18.8.3
9132A–AUTO–10/08
DRAFT
ADC Conversion Result
Single Ended Conversion
Unipolar Differential Conversion
Bipolar Differential Conversion
After the conversion is complete (ADIF is high), the conversion result can be found in the ADC
Result Registers (ADCL, ADCH). The form of the conversion result depends on the type of the
conversion as there are three types of conversions: single ended conversion, unipolar differen-
tial conversion and bipolar differential conversion.
For single ended conversion, the result is:
where V
Table 4-57 on page 229
0x3FF represents the selected voltage reference minus one LSB. The result is presented in
one-sided form, from 0x3FF to 0x000.
If differential channels and an unipolar input mode are used, the result is:
where V
and V
230). The voltage on the positive pin must always be larger than the voltage on the negative pin
or otherwise the voltage difference is saturated to zero. The result is presented in one-sided
form, from 0x000 (0
As default the ADC converter operates in the unipolar input mode, but the bipolar input mode
can be selected by writing the BIN bit in the ADCSRB register to one. In the bipolar input mode
two-sided voltage differences are allowed and thus the voltage on the negative input pin can
also be larger than the voltage on the positive input pin. If differential channels and a bipolar
input mode are used, the result is:
where V
and V
0x200 (-512
However, if the signal is not bipolar by nature (9 bits + sign as the 10th bit), this scheme loses
one bit of the converter dynamic range. Then, if the user wants to perform the conversion with
the maximum dynamic range, the user can perform a quick polarity check of the result and use
the unipolar differential conversion with selectable differential input pair. When the polarity check
is performed, it is sufficient to read the MSB of the result (ADC9 in ADCH register). If the bit is
one, the result is negative, and if this bit is zero, the result is positive.
ADC
ADC
ADC
=
=
=
REF
REF
V
---------------------------- -
-----------------------------------------------------------
------------------------------------------------------- -
IN
POS
POS
V
V
IN
the selected voltage reference. The result is presented in two’s complement form, from
the selected voltage reference (see
POS
POS
V
is the voltage on the selected input pin and V
REF
d
is the voltage on the positive input pin, V
is the voltage on the positive input pin, V
) through 0x000 (+0
1024
–
–
V
V
V
V
REF
NEG
NEG
REF
d
) to 0x3FF (+1023
1024
512
and
GAIN
Table 4-58 on page
GAIN
d
) to 0x1FF (+511
ATA6616/ATA6617 [Preliminary]
d
). The GAIN is either 8x or 20x.
Table 4-57 on page 229
d
230). 0x000 represents analog ground, and
). The GAIN is either 8x or 20x.
NEG
NEG
REF
the voltage on the negative input pin,
the voltage on the negative input pin,
the selected voltage reference (see
and
Table 4-58 on page
227