Datasheet
REV. B
ADuC824
–66–
C1+
V+
C1–
C2+
C2–
V–
T2OUT
R2IN
V
CC
GND
T1OUT
R1IN
R1OUT
T1IN
T2IN
R2OUT
ADM202
DV
DD
27
34
33
31
30
29
28
39
38
37
36
35
32
40
47
46
44
43
42
41
52
51
50
49
48
45
DV
DD
1k
DV
DD
1k
2-PIN HEADER FOR
EMULATION ACCESS
(NORMALLY OPEN)
DOWNLOAD/DEBUG
ENABLE JUMPER
(NORMALLY OPEN)
32.766kHz
DV
DD
1
9-PIN D-SUB
FEMALE
2
3
4
5
6
7
8
9
AV
DD
V
REF
+
V
REF
–
A
IN
+
A
IN
–
200A/400A
EXCITATION
CURRENT
R2
510
RTD
R1
5.6k
AV
DD
AGND
P1.2I
EXC
1/DAC
REFIN–
REFIN+
P1.4/AIN1
P1.5/AIN2
DV
DD
DGND
PSEN
EA
DGND
DV
DD
XTAL2
XTAL1
RESET
RXD
TXD
DV
DD
DGND
ADM810
V
CC
RST
GND
DV
DD
NOT CONNECTED IN THIS EXAMPLE
DV
DD
Figure 53. Typical System Configuration
comes with the single-pin emulator available from Accutron Limited
(www.accutron.com), use a 2-pin 0.1-inch pitch “Friction Lock”
header from Molex (www.molex.com) such as their part number
22-27-2021. Be sure to observe the polarity of this header. As
represented in Figure 53, when the Friction Lock tab is at the
right, the ground pin should be the lower of the two pins (when
viewed from the top).
Enhanced-Hooks Emulation Mode
ADuC824 also supports enhanced-hooks emulation mode. An
enhanced-hooks-based emulator is available from Metalink
Corporation (www.metaice.com). No special hardware support
for these emulators needs to be designed onto the board since
these are “pod-style” emulators where users must replace the chip
on their board with a header device that the emulator pod plugs
into. The only hardware concern is then one of determining if
adequate space is available for the emulator pod to fit into the
system enclosure.
Typical System Configuration
A typical ADuC824 configuration is shown in Figure 53. It sum-
marizes some of the hardware considerations discussed in the
previous paragraphs.
Figure 53 also includes connections for a typical analog mea-
surement application of the ADuC824, namely an interface to
an RTD (Resistive Temperature Device). The arrangement
shown is commonly referred to as a 4-wire RTD configuration.
Here, the on-chip excitation current sources are enabled to excite
the sensor. An external differential reference voltage is generated
by the current sourced through resistor R1. This current also
flows directly through the RTD, which generates a differential
voltage directly proportional to temperature. This differential
voltage is routed directly to the positive and negative inputs of
the primary ADC (AIN1, AIN2 respectively). A second external
resistor, R2, is used to ensure that absolute analog input voltage
on the negative input to the primary ADC stays within that
specified for the ADuC824, i.e., AGND + 100 mV.
It should also be noted that variations in the excitation current
do not affect the measurement system as the input voltage from
the RTD and reference voltage across R1 vary ratiometrically with
the excitation current. Resistor R1 must, however, have a low
temperature coefficient to avoid errors in the reference voltage
over temperature.