EVAL-ADUC842QSZ Analog Devices Inc, EVAL-ADUC842QSZ Datasheet - Page 28

• Manufacturer Part Number: EVAL-ADUC842QSZ
• Description: Analog MCU Evaluation Board
• Manufacturer: Analog Devices Inc
• Series: QuickStart™ Kitr
• Type: MCUr

Specifications of EVAL-ADUC842QSZ

• Silicon Manufacturer: Analog Devices
• Core Architecture: 8052
• Silicon Core Number: ADuC842
• Tool / Board Applications: General Purpose MCU, MPU, DSP, DSC
• Mcu Supported Families: ADUC8xx
• Contents: Evaluation Board, Power Supply, Cable, Software and Documentation
• Development Tool Type: Hardware - Eval/Demo Board
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: ADuC824
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

ADuC841/ADuC842/ADuC843
Table 11. Some Single-Supply Op Amps
Op Amp Model
OP281/OP481
OP191/OP291/OP491
OP196/OP296/OP496
OP183/OP283
OP162/OP262/OP462
AD820/AD822/AD824
AD823
Keep in mind that the ADC’s transfer function is 0 V to V
and that any signal range lost to amplifier saturation near
ground will impact dynamic range. Though the op amps in
Table 11 are capable of delivering output signals that very
closely approach ground, no amplifier can deliver signals all the
way to ground when powered by a single supply. Therefore, if a
negative supply is available, you might consider using it to
power the front end amplifiers. If you do, however, be sure to
include the Schottky diodes shown in Figure 31 (or at least the
lower of the two diodes) to protect the analog input from
undervoltage conditions. To summarize this section, use the
circuit in Figure 31 to drive the analog input pins of the parts.
Voltage Reference Connections
The on-chip 2.5 V band gap voltage reference can be used as the
reference source for the ADC and DACs. To ensure the accuracy
of the voltage reference, you must decouple the C
ground with a 0.47 µF capacitor, as shown in Figure 32. Note
that this is different from the ADuC812/ADuC831/ADuC832.
If the internal voltage reference is to be used as a reference for
external circuitry, the C
buffer must be used in this case to ensure that no current is
drawn from the C
of an internal node within the buffer block, and its voltage is
critical for ADC and DAC accuracy. The parts power up with
their internal voltage reference in the off state.
BUFFER
V
REF
0.47 µ F
Figure 32. Decoupling V
REF
= NC
C
REF
pin itself. The voltage on the C
REF
ADuC841/ADuC842/ADuC843
output should be used. However, a
Characteristics
Micropower
I/O Good up to V
I/O to V
High Gain-Bandwidth Product
High GBP, Micro Package
FET Input, Low Cost
FET Input, High GBP
51 Ω
BUFFER
REFERENCE
DD
BAND GAP
, Micropower, Low Cost
REF
2.5V
and C
DD
REF
, Low Cost
REF
REF
pin to
pin is that
REF
,
Rev. 0 | Page 28 of 88
If an external voltage reference is preferred, it should be
connected to the C
ADCCON1 SFR must be set to 1 to switch in the external
reference voltage.
To ensure accurate ADC operation, the voltage applied to C
must be between 1 V and AV
input signals are proportional to the power supply (such as in
some strain gage applications), it may be desirable to connect
the C
with a reference voltage below 1 V, however, may incur loss of
accuracy, eventually resulting in missing codes or non-
monotonicity. For that reason, do not use a reference voltage
lower than 1 V.
Configuring the ADC
The parts’ successive approximation ADC is driven by a divided
down version of the master clock. To ensure adequate ADC
operation, this ADC clock must be between 400 kHz and
8.38 MHz. Frequencies within this range can be achieved easily
with master clock frequencies from 400 kHz to well above
16 MHz, with the four ADC clock divide ratios to choose from.
For example, set the ADC clock divide ratio to 8 (i.e., ADCCLK
= 16.777216 MHz/8 = 2 MHz) by setting the appropriate bits in
ADCCON1 (ADCCON1.5 = 1, ADCCON1.4 = 0). The total
ADC conversion time is 15 ADC clocks, plus 1 ADC clock for
synchronization, plus the selected acquisition time (1, 2, 3, or 4
ADC clocks). For the preceding example, with a 3-clock
acquisition time, total conversion time is 19 ADC clocks (or
9.05 µs for a 2 MHz ADC clock).
In continuous conversion mode, a new conversion begins each
time the previous one finishes. The sample rate is then simply
the inverse of the total conversion time described previously. In
the preceding example, the continuous conversion mode sample
rate is 110.3 kHz.
REF
REFERENCE
pin directly to AV
EXTERNAL
VOLTAGE
V
V
DD
Figure 33. Using an External Voltage Reference
REF
0.1µ F
= NC
C
REF
REF
pin as shown in Figure 33. Bit 6 of the
ADuC841/ADuC842/ADuC843
51 Ω
DD
1 = EXTERNAL
0 = INTERNAL
. Operation of the ADC or DACs
DD
ADCCON1.6
. In situations where analog
REFERENCE
BAND GAP
2.5V
BUFFER
REF