AD7938-6 Analog Devices, AD7938-6 Datasheet - Page 22

• Manufacturer Part Number: AD7938-6
• Description: 8-Channel, 625 kSPS, 12-Bit Parallel ADCs with a Sequencer
• Manufacturer: Analog Devices

Specifications of AD7938-6

• Resolution (bits): 12bit
• # Chan: 8
• Sample Rate: 625kSPS
• Interface: Par
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: Uni (Vref),Uni (Vref) x 2
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

AD7938-6
For example, if operating in differential mode and the reference
is sourced from V
This is because the analog input signal range now extends to 2 ×
V
differential modes, the user must ensure that V
when using the 0 V to V
range that 2 × V
In all cases, the sp cifie
The performance of the part with different r
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
AD7938-6 transfer function and add to specified full-scale
errors on the part.
Table 12 lists examples o
Analog Devices that can be used. Figure 34 shows a typical
connection diagram for an external reference.
Table 12. Examples of Suitable Voltage References
Reference
AD780
ADR421
ADR420
DD
V
*ADDITIONAL PINS OMITTED FOR CLARITY.
DD
0.1µF
, which exceeds maximum rating conditions. In the pseudo
10nF
Output
Voltage
2.5/3
2.5
2.04
Figure 34. Typical V
REF
8
DD
e
0.1µF
+V
, the 0 V to 2 × V
NC
IN−
d r
REF
f suitable voltage references from
≤ V
efer c
NC = NO CONNECT
range, or when using the 2 × V
1
2
3
4
Initial Accuracy
(% Maximum)
0.04
0.04
0.05
DD
+V
TEMP
GND
en e is 2.5 V.
O/PSELECT
REF
.
IN
AD780
Connection Diagram
V
TRIM
OUT
REF
range cannot be used.
8
7
6
5
2.5V
eference values is
NC
NC
NC
REF
Opera
Current (μA
1000
500
500
+ V
AD7938-6*
0.1µF
IN−
ting
≤ V
V
REF
REF
)
Rev. C | Page 22 of 32
DD
Digital Inputs
The digital inputs applied to the AD7938-6 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 were applied prior to V
V
The AD7938-6 has a V
at which the parallel interface operates. V
to easily interface to 3 V and 5 V processors.
For example, if the AD7938-6 is operated with an AV
and the V
has better dynamic performance with a V
being able to interface directly to 3 V processors. Care should
be taken to ensure V
0.3 V (see the Absolute Maximum Ratings section).
DRIVE
DD
+ 0.3 V limit as on the analog inputs.
DD
Input
+ 0.3 V limit is the fact that power supply sequencing
DRIVE
pin is powered from a 3 V supply, the AD7938-6
DRIVE
DRIVE
does not exceed V
feature. V
DRIVE
DRIVE
DD
controls the voltage
DD
of 5 V while still
allows the ADC
by more than
Data Sheet
DD
of 5 V
DD.
DD
,