AD7934BRUZ Analog Devices Inc, AD7934BRUZ Datasheet - Page 22

• Manufacturer Part Number: AD7934BRUZ
• Description: IC ADC 12BIT 4CH 1.5MSPS 28TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7934BRUZ

• Data Interface: Parallel
• Number Of Bits: 12
• Sampling Rate (per Second): 1.5M
• Number Of Converters: 1
• Power Dissipation (max): 13.5mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TSSOP (0.173", 4.40mm Width)
• Resolution (bits): 12bit
• Input Channel Type: Differential, Single Ended
• Supply Voltage Range - Analogue: 2.7V To 5.25V
• Supply Voltage Range - Digital: 2.7V To 5.25V
• Supply: RoHS Compliant
• Sampling Rate: 1.5MSPS
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD7933/AD7934
starts the sequence again. The WR input must be kept high to
ensure that the control register is not accidentally overwritten
and the sequence interrupted. This pattern continues until the
AD7933/AD7934 is written to. Figure 31 shows the flowchart of
the consecutive sequence mode.
REFERENCE
The AD7933/AD7934 can operate with either the on-chip
reference or an external reference. The internal reference is
selected by setting the REF bit in the internal control register to 1.
A block diagram of the internal reference circuitry is shown in
Figure 32. The internal reference circuitry includes an on-chip
2.5 V band gap reference and a reference buffer. When using the
internal reference, decouple the V
0.47 μF capacitor. This internal reference not only provides the
reference for the analog-to-digital conversion, but it can also be
used externally in the system. It is recommended that the
reference output is buffered using an external precision op amp
before applying it anywhere in the system.
Alternatively, an external reference can be applied to the
V
reference input is selected by setting the REF bit in the internal
control register to 0. The external reference input range is 0.1 V
to V
reference value, the maximum analog input range (V
never greater than V
ratings of the device. For example, if operating in differential
mode and the reference is sourced from V
range cannot be used. This is because the analog input signal
range now extends to 2 × V
rating conditions. In the pseudo differential modes, the user
must ensure that V
range, or when using the 2 × V
In all cases, the specified reference is 2.5 V.
REFIN
DD
/V
. It is important to ensure that, when choosing the
REFOUT
Figure 32. Internal Reference Circuit Block Diagram
Figure 31. Consecutive Sequence Mode Flow Chart
V
V
REFOUT
REFIN
SELECTED FINAL CHANNEL ON ADD1 AND ADD0
pin of the AD7933/AD7934. An external
CONTINUOUSLY CONVERT ON A CONSECUTIVE
SEQUENCE OF CHANNELS FROM CHANNEL 0
SET UP OPERATING MODE, ANALOG INPUT
/
UP TO AND INCLUDING THE PREVIOUSLY
WRITE TO THE CONTROL REGISTER TO
AND OUTPUT CONFIGURATION SELECT
FINAL CHANNEL (ADD1 AND ADD0) IN
REF
DD
+ V
WITH EACH CONVST PULSE.
CONSECUTIVE SEQUENCE.
+ 0.3 V to comply with the maximum
SET SEQ0 = 1 SEQ1 = 1.
BUFFER
IN−
DD
≤ V
POWER ON
REF
, which exceeds the maximum
REFIN
range that 2 × V
DD
ADC
when using the 0 V to V
/V
REFOUT
REFERENCE
AD7933/
AD7934
DD
pin to AGND with a
, the 0 V to 2 × V
REF
+ V
IN MAX
IN−
≤ V
) is
REF
Rev. B | Page 22 of 32
DD
REF
.
The performance of the part with different reference values is
shown in Figure 9 to Figure 11. The value of the reference sets
the analog input span and the common-mode voltage range.
Errors in the reference source result in gain errors in the
AD7933/AD7934 transfer function and add to the specified
full-scale errors on the part.
Table 12 lists suitable voltage references available from Analog
Devices that can be used. Figure 33 shows a typical connection
diagram for an external reference.
Table 12. Examples of Suitable Voltage References
Reference
AD780
ADR421
ADR420
Digital Inputs
The digital inputs applied to the AD7933/AD7934 are not
limited by the maximum ratings that limit the analog inputs.
Instead, the digital inputs applied can go to 7 V and are not
restricted by the V
Another advantage of the digital inputs not being restricted by
the V
issues are avoided. If any of these inputs are applied before V
there is no risk of latch-up as there would be on the analog inputs
if a signal greater than 0.3 V was applied prior to V
V
The AD7933/AD7934 have a V
voltage at which the parallel interface operates. V
ADC to easily interface to 3 V and 5 V processors.
For example, if the AD7933/AD7934 are operated with a V
of 5 V, and the V
AD7933/AD7934 have better dynamic performance with a
V
Ensure that V
the Absolute Maximum Ratings section).
V
*ADDITIONAL PINS OMITTED FOR CLARITY.
DD
0.1µF
DRIVE
DD
of 5 V while still being able to interface to 3 V processors.
DD
Input
+ 0.3 V limit is the fact that power supply sequencing
10nF
Output
Voltage (V)
2.5/3
2.5
2.048
DRIVE
Figure 33. Typical V
DRIVE
0.1µF
DD
does not exceed V
NC
+ 0.3 V limit that is on the analog inputs.
pin is powered from a 3 V supply, the
NC = NO CONNECT
1
2
3
4
+V
TEMP
GND
Initial Accuracy
(% maximum)
0.04
0.04
0.05
O/P SELECT
IN
REF
AD780
DRIVE
Connection Diagram
TRIM
V
OUT
feature. V
DD
by more than 0.3 V (see
8
7
6
5
2.5V
NC
NC
NC
DRIVE
Operating
Current (μA)
1000
500
500
DRIVE
DD
controls the
.
AD7933/
AD7934*
allows the
0.1µF
DD
DD
V
REF
,