EVAL-ADUC836QS AD [Analog Devices], EVAL-ADUC836QS Datasheet - Page 68

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

Typical System Confi guration
A typical ADuC836 confi guration is shown in Figure 66. It sum-
ma riz es some of the hardware considerations discussed in the
previous paragraphs.
Figure 66 also includes connections for a typical analog mea-
sure ment application of the ADuC836, namely an interface to an
RTD (Resistive Temperature Device). The arrangement shown is
commonly referred to as a 4-wire RTD confi guration.
Here, the on-chip excitation current sources are enabled to
excite the sensor. The excitation current fl ows directly through
the RTD, generating a voltage across the RTD proportional to
ADuC836
200 A/400 A
EXCITATION
CURRENT
RTD
5.6k
*EXTERNAL UART TRANSCEIVER INTEGRATED IN SYSTEM OR AS
R
PART OF AN EXTERNAL DONGLE AS DESCRIBED IN uC006.
RS232 INTERFACE*
REF
C1+
V+
C1–
C2+
C2–
V–
T2OUT
R2IN
AV
ADM3202
DD
R1OUT
R2OUT
T1OUT
R1IN
GND
T1IN
T2IN
V
CC
Figure 66. Typical System Confi guration
P1.3/AIN5/DAC
P1.2/I
AV
AGND
REFIN–
REFIN+
P1.4/AIN1
P1.5/AIN2
52
DD
DV
51
EXC
DD
50
1/DAC
49
DV
48
DD
DV
ADuC836
47
STANDARD D-TYPE
DD
CONNECTOR TO
SERIAL COMMS
–68–
46
PC HOST
45
its resistance. This differential voltage is routed directly to the
positive and negative inputs of the primary ADC (AIN1, AIN2,
respectively). The same current that excited the RTD also fl ows
through a series resistance R
reference V
variations in the excitation current do not affect the mea sure ment
system as the input voltage from the RTD and reference voltage
across R
tor R
avoid errors in the reference voltage over temperature. R
also be large enough to generate at least a 1 V voltage reference.
DOWNLOAD/DEBUG
(NORMALLY OPEN)
1
3
4
6
7
8
ENABLE JUMPER
44
2
5
9
1k
43
REF
ALL CAPACITORS IN THIS EXAMPLE ARE
0.1 F CERAMIC CAPACITORS.
42
REF
NOT CONNECTED IN THIS EXAMPLE
must, however, have a low tem per a ture coeffi cient to
41
XTAL2
XTAL1
DGND
REF
DV
vary ratiometrically with the ex ci ta tion current. Resis-
1k
40
DD
. The ratiometric voltage reference en sures that
DV
39
38
37
36
35
34
33
32
31
30
29
28
27
DD
DV
32.768kHz
DD
2-PIN HEADER FOR
EMULATION ACCESS
(NORMALLY OPEN)
REF
, generating a ratiometric voltage
REF
REV. 0
must