EVAL-ADUC836QS AD [Analog Devices], EVAL-ADUC836QS Datasheet - Page 24

• Manufacturer Part Number: EVAL-ADUC836QS
• Description: MicroConverter, Dual 16-Bit ADCs with Embedded 62 kB Flash MCU
• Manufacturer: AD [Analog Devices]

Auxiliary ADC
The auxiliary ADC is intended to convert supplementary inputs
such as those from a cold junction diode or thermistor. This ADC
is not buffered and has a fi xed input range of 0 V to 2.5 V (as sum ing
an external 2.5 V reference). The single-ended inputs can be driven
from AIN3, AIN4, or AIN5 pins, or directly from the on-chip
temperature sensor voltage. A block diagram of the aux il ia ry ADC
is shown in Figure 8.
Analog Input Channels
The primary ADC has four associated analog input pins (labeled
AIN1 to AIN4) that can be confi gured as two fully dif fer en tial input
channels. Channel selection bits in the ADC0CON SFR detailed
in Table VI allow three combinations of differential pair selection
as well as an additional shorted input option (AIN2–AIN2).
ADuC836
TEMPERATURE
ON-CHIP
SENSOR
CONVERSION CYCLE. CHOPPING
ANALOG INPUT CHOPPING
THE INPUTS ARE ALTERNATELY
THE MULTIPLEXER IS CONTROLLED
AIN3
AIN4
AIN5
EXTERNAL SINGLE ENDED INPUTS
OR THE ON-CHIP TEMP. SENSOR.
OFFSET AND OFFSET DRIFT
ALLOWS SELECTION OF THREE
A DIFFERENTIAL MULTIPLEXER
VIA THE CHANNEL SELECTION
REVERSED THROUGH THE
YIELDS EXCELLENT ADC
ANALOG MULTIPLEXER
PERFORMANCE.
BITS IN ADC1CON.
MUX
MU
X
CHOP
REFIN(–) REFIN(+)
REFERENCE VOLTAGE IS SELECTED
THE EXTERNAL REFERENCE INPUT
DIFFERENTIAL REFERENCE
TO THE ADuC836 IS DIFFERENTIAL
AND FACILITATES RATIOMETRIC
CIRCUITRY TESTS FOR OPEN OR
VIA THE XREF1 BIT IN ADC1CON.
SHORTED REFERENCE INPUTS.
OPERATION. THE EXTERNAL
STREAM (THE OUTPUT OF WHICH
THE MODULATOR PROVIDES A
HIGH FREQUENCY 1-BIT DATA
REPRESENTS THE SAMPLED
REFERENCE DETECT
THE DUTY CYCLE OF WHICH
IS ALSO CHOPPED) TO THE
ANALOG INPUT VOLTAGE.
Figure 8. Auxiliary ADC Block Diagram
- MODULATOR
DIGITAL FILTER,
MODULATOR
-
- ADC
PROGRAMMABLE
DIGITAL FILTER
–24–
The auxiliary ADC has three external input pins (labeled AIN3
to AIN5) as well as an internal connection to the on-chip tem-
perature sensor. All inputs to the auxiliary ADC are single-ended
inputs referenced to the AGND on the part. Chan nel selection
bits in the ADC1CON SFR detailed in Table VII allow selection
of one of four inputs.
Two input multiplexers switch the selected input channel to the
on-chip buffer amplifi er in the case of the primary ADC and
directly to the - modulator input in the case of the auxiliary
ADC. When the analog input channel is switched, the settling
time of the part must elapse before a new valid word is available
from the ADC.
ENSURES 16 BITS NO MISSING
CODES. THE ENTIRE -
IS CHOPPED TO REMOVE
THE - ARCHITECTURE
QUANTIZATION NOISE INTRODUCED
BY THE MODULATOR. THE UPDATE
DRIFT ERRORS.
PROGRAMMABLE DIGITAL
RATE AND BANDWIDTH OF THIS
FILTER ARE PROGRAMMABLE
THE SINC 3 FILTER REMOVES
- ADC
VIA THE SF SFR.
CHOP
FILTER
ADC
AVERAGE
OUTPUT
AS PART OF THE CHOPPING
WITH ITS PREDECESSOR
IMPLEMENTATION, EACH
SUMMED AND AVERAGED
TO NULL ADC CHANNEL
OUTPUT AVERAGE
DATA-WORD OUTPUT
FROM THE FILTER IS
OFFSET ERRORS.
DIGITAL FILTER IS SCALED BY
THE OUPUT WORD FROM THE
THE CONVERSION RESULT.
SCALING
OUTPUT
COEFFICIENTS BEFORE
OUTPUT SCALING
BEING PROVIDED AS
THE CALIBRATION
RESULT WRITTEN
TO ADC1H/L SFRs
DIGTAL OUTPUT
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