AD7450ABRMZ Analog Devices Inc, AD7450ABRMZ Datasheet - Page 20

• Manufacturer Part Number: AD7450ABRMZ
• Description: IC ADC 12BIT DIFF IN 1MSPS 8MSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7450ABRMZ

• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Bits: 12
• Sampling Rate (per Second): 1M
• Number Of Converters: 1
• Power Dissipation (max): 9.25mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Resolution (bits): 12bit
• Sampling Rate: 1MSPS
• Input Channel Type: Differential
• Supply Voltage Range - Analog: 2.7V To 5.25V
• Supply Current: 1.95mA
• Digital Ic Case Style: SOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7450CBZ - BOARD EVALUATION FOR AD7450
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

AD7440/AD7450A
Example 1
If V
Thus, when operating at V
from 100 mV to a maximum value of 3.5 V. When V
V
Example 2
If V
Therefore,
Thus, when operating at V
from 100 mV to a maximum value of 2.2 V. When V
V
These examples show that the maximum reference applied to
the AD7440/AD7450A is directly dependent on the value
applied to V
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 AD7440/AD7450A transfer function
and add to specified full-scale errors on the part. A 0.1 μF
capacitor should be used to decouple the V
Figure 38 shows a typical connection diagram for the V
Table 6 lists examples of suitable voltage references.
V
*ADDITIONAL PINS OMITTED FOR CLARITY
DD
REF
REF
0.1μF
DD
DD
max = 2 V.
max = 3.17 V.
V
V
Therefore
3 × V
V
V
V
3 × V
V
= 3 V, then V
= 5 V, then V
IN
IN
REF
IN
IN
REF
max = V
max = V
max = V
max = V
Figure 38. Typical V
max = 3.5 V
max = 2.2 V
10nF
REF
REF
DD
/2 = 5.3 V
/2 = 3.3 V
.
0.1μF
DD
REF
DD
REF
IN
IN
+ 0.3
+ 0.3
+ V
+ V
NC
max = 3.3 V.
max = 5.3 V.
REF
REF
REF
NC = NO CONNECT
1
2
3
4
DD
/2
DD
/2
Connection Diagram for V
V
TEMP
GND
= 3 V, the value of V
IN
= 5 V, the value of V
AD780
OPSEL
V
TRIM
OUT
8
7
6
5
2.5V
REF
NC
NC
NC
pin to GND.
DD
REF
REF
AD7450A*
AD7440/
= 5 V
DD
can range
DD
can range
0.1μF
= 4.75 V,
= 2.7 V,
REF
pin.
V
V
REF
DD
Rev. C | Page 20 of 28
Table 6. Examples of Suitable Voltage References
Reference
AD780
ADR421
ADR420
SINGLE-ENDED OPERATION
When supplied with a 5 V power supply, the AD7440/AD7450A
can handle a single-ended input. The design of these devices is
optimized for differential operation, so with a single-ended
input, performance degrades. Linearity degrades by typically
0.2 LSB, the full-scale errors degrade typically by 1 LSB, and ac
performance is not guaranteed.
To operate the AD7440/AD7450A in single-ended mode, the
V
biased to the appropriate voltage corresponding to the midscale
code transition. This voltage is the common mode, which is a
fixed dc voltage (usually the reference). The V
around this value and should have a voltage span of 2 × V
make use of the full dynamic range of the part. The input signal
therefore has peak-to-peak values of common mode ±V
the analog input is unipolar, an op amp in a noninverting unity
gain configuration can be used to drive the V
operates from a single supply, so it is necessary to level shift
ground-based bipolar signals to comply with the input
requirements. An op amp can be configured to rescale and level
shift the ground-based bipolar signal, so it is compatible with
the selected input range of the AD7440/AD7450A (Figure 39).
Figure 39. Applying a Bipolar Single-Ended Input to the AD7440/AD7450A
IN+
+2.5V
–2.5V
input is coupled to the signal source, while the V
0V
Output
Voltage (V)
2.5/3
2.5
2.048
V
IN
R
R
R
EXTERNAL
V
REF
(2.5V)
R
Initial
Accuracy (%)
0.04
0.04
0.05
0.1μF
2.5V
5V
0V
V
V
IN+
IN+
IN–
IN+
AD7450A
AD7440/
pin. The ADC
input swings
Operating
Current (μA)
1000
500
500
IN–
V
REF
REF
input is
REF
. If
to