AD7712ARZ Analog Devices Inc, AD7712ARZ Datasheet - Page 19

• Manufacturer Part Number: AD7712ARZ
• Description: IC ADC SIGNAL COND LC2MOS 24SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD7712ARZ

• Data Interface: Serial
• Number Of Bits: 24
• Sampling Rate (per Second): 1.03k
• Number Of Converters: 1
• Power Dissipation (max): 45mW
• Voltage Supply Source: Analog and Digital, Dual ±
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Resolution (bits): 24bit
• Sampling Rate: 1.028kSPS
• Input Channel Type: Differential
• Supply Voltage Range - Digital: 4.75V To 5.25V
• Supply Current: 4.5mA
• Digital Ic Case Style: SOIC
• Number Of Elements: 1
• Resolution: 24Bit
• Architecture: Delta-Sigma
• Sample Rate: 1.028KSPS
• Input Polarity: Unipolar/Bipolar
• Input Type: Voltage
• Rated Input Volt: 5/20/±5/±20V
• Differential Input: Yes
• Power Supply Requirement: Single/Dual
• Single Supply Voltage (typ): 5/10V
• Single Supply Voltage (min): 4.75V
• Single Supply Voltage (max): 10.5V
• Dual Supply Voltage (typ): ±5/-5/10V
• Dual Supply Voltage (min): ±4.75V
• Dual Supply Voltage (max): -5.25/10.5V
• Power Dissipation: 52.5mW
• Integral Nonlinearity Error: ±0.003%FSR
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 24
• Package Type: SOIC W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Cal Type
Self-Cal
System Cal
System Cal
System Offset Cal
Background Cal
Span and Offset Limits
Whenever a system calibration mode is used, there are limits on
the amount of offset and span that can be accommodated. The
range of input span in both the unipolar and bipolar modes for
AIN1 has a minimum value of 0.8
mum value of 2.1
a factor of 4 higher.
The amount of offset that can be accommodated depends on
whether the unipolar or bipolar mode is being used. This offset
range is limited by the requirement that the positive full-scale
calibration limit is ≤ 1.05
the offset range plus the span range cannot exceed 1.05
GAIN for AIN1. If the span is at its minimum (0.8
GAIN), the maximum the offset can be is (0.25
for AIN1. For AIN2, both ranges are multiplied by a factor of 4.
In the bipolar mode, the system offset calibration range is again
restricted by the span range. The span range of the converter in
bipolar mode is equidistant around the voltage used for the
zero-scale point, thus the offset range plus half the span range
cannot exceed (1.05 × V
set to 2 × V
± (0.05 × V
tion exceed the input overrange limits ± (1.05 × V
AIN1. If the span range is set to the minimum ± (0.4 × V
GAIN), the maximum
GAIN) for AIN1. Once again, for AIN2, both ranges are
multiplied by a factor of 4.
POWER-UP AND CALIBRATION
On power-up, the AD7712 performs an internal reset, which
sets the contents of the control register to a known state. How-
ever, to ensure correct calibration for the device, a calibration
routine should be performed after power-up.
The power dissipation and temperature drift of the AD7712 are
low and no warm-up time is required before the initial calibra-
tion is performed. However, if an external reference is being
used, this reference must have stabilized before calibration is
initiated.
Drift Considerations
The AD7712 uses chopper stabilization techniques to minimize
input offset drift. Charge injection in the analog switches and dc
leakage currents at the sampling node are the primary sources of
offset voltage drift in the converter. The dc input leakage cur-
rent is essentially independent of the selected gain. Gain drift
within the converter depends primarily upon the temperature
tracking of the internal capacitors. It is not affected by leakage
currents.
REV. F
REF
REF
/GAIN) before the endpoints of the transfer func-
/GAIN, the offset span cannot move more than
V
REF
allowable offset range is ± (0.65
MD2, MD1, MD0
0, 0, 1
0, 1, 0
0, 1, 1
1, 0, 0
1, 0, 1
REF
/GAIN. For AIN2, both numbers are
/GAIN) for AIN1. If the span is
V
REF
/GAIN for AIN1. Therefore,
V
REF
/GAIN and a maxi-
Table VI. Calibration Truth Table
V
REF
Zero-Scale Cal
Shorted Inputs
AIN
–
AIN
Shorted Inputs
REF
/GAIN) for
/GAIN)
V
× V
REF
REF
V
/
REF
REF
/
/
/
–19–
Measurement errors due to offset drift or gain drift can be elimi-
nated at any time by recalibrating the converter or by operating
the part in the background calibration mode. Using the system
calibration mode can also minimize offset and gain errors in the
signal conditioning circuitry. Integral and differential linearity
errors are not significantly affected by temperature changes.
POWER SUPPLIES AND GROUNDING
Since the analog inputs and reference input are differential,
most of the voltages in the analog modulator are common-mode
voltages. V
currents flowing in the analog modulator. As a result, the V
input should be driven from a low impedance to minimize
errors due to charging/discharging impedances on this line.
When the internal reference is used as the reference source for
the part, AGND is the ground return for this reference voltage.
The analog and digital supplies to the AD7712 are independent
and separately pinned out to minimize coupling between the
analog and digital sections of the device. The digital filter will
provide rejection of broadband noise on the power supplies,
except at integer multiples of the modulator sampling frequency.
The digital supply (DV
supply (AV
rate analog and digital supplies are used, the decoupling scheme
shown in Figure 10 is recommended. In systems where AV
5 V and DV
are driven from the same 5 V supply, although each supply
should be decoupled separately as shown in Figure 10. It is
preferable that the common supply is the system’s analog
5 V supply.
It is also important that power is applied to the AD7712 before
signals at REF IN, AIN, or the logic input pins in order to avoid
excessive current. If separate supplies are used for the AD7712
and the system digital circuitry, then the AD7712 should be
powered up first. If it is not possible to guarantee this, then
current limiting resistors should be placed in series with the
logic inputs.
V
–
AIN
V
V
Full-Scale Cal
ANALOG
SUPPLY
REF
REF
REF
10 F
Figure 10. Recommended Decoupling Scheme
BIAS
DD
DD
) by more than 0.3 V in normal operation. If sepa-
0.1 F
provides the return path for most of the analog
= 5 V, it is recommended that AV
DD
) must not exceed the analog positive
Sequence
One-Step
Two-Step
Two-Step
One-Step
One-Step
AV
DD
AD7712
DV
DD
0.1 F
Duration
9
4
4
9
6
1/Output Rate
1/Output Rate
1/Output Rate
1/Output Rate
1/Output Rate
AD7712
DIGITAL 5V
SUPPLY
DD
and DV
DD
BIAS
DD
=