AD7710ARZ Analog Devices Inc, AD7710ARZ Datasheet - Page 16

• Manufacturer Part Number: AD7710ARZ
• Description: IC ADC 24BIT DIFF INP 24-SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD7710ARZ

• 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
• Input Channel Type: Differential
• Supply Voltage Range - Digital: 4.75V To 5.25V
• Supply Current: 4.5mA
• Digital Ic Case Style: SOIC
• No. Of Pins: 24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD7710
Bipolar/Unipolar Inputs
The two analog inputs on the AD7710 can accept either unipo-
lar or bipolar input voltage ranges. Bipolar or unipolar options
are chosen by programming the B/U bit of the control register.
This programs both channels for either type of operation.
Programming the part for either unipolar or bipolar operation
does not change any of the input signal conditioning; it sim-
ply changes the data output coding, using binary for unipolar
inputs and offset binary for bipolar inputs.
The input channels are differential and, as a result, the voltage
to which the unipolar and bipolar signals are referenced is the
voltage on the AIN(–) input. For example, if AIN(–) is 1.25 V
and the AD7710 is configured for unipolar operation with a
gain of 1 and a V
AIN(+) input is 1.25 V to 3.75 V. If AIN(–) is 1.25 V and
the AD7710 is configured for bipolar mode with a gain of 1
and a V
input is –1.25 V to +3.75 V.
REFERENCE INPUT/OUTPUT
The AD7710 contains a temperature compensated 2.5 V refer-
ence which has an initial tolerance of 1%. This reference volt-
age is provided at the REF OUT pin, and it can be used as the
reference voltage for the part by connecting the REF OUT pin
to the REF IN(+) pin. This REF OUT pin is a single-ended
output, referenced to AGND, which is capable of providing up
to 1 mA to an external load. In applications where REF OUT is
connected to REF IN(+), REF IN(–) should be tied to AGND
to provide the nominal 2.5 V reference for the AD7710.
The reference inputs of the AD7710, REF IN(+) and REF IN(–)
provide a differential reference input capability. The common-
mode range for these differential inputs is from V
The nominal differential voltage, V
is 2.5 V for specified operation, but the reference voltage can go
to 5 V with no degradation in performance if the absolute value
of REF IN(+) and REF IN(–) does not exceed its AV
V
The part is also functional with V
with degraded performance because the output noise will, in
terms of LSB size, be larger. REF IN(+) must always be greater
than REF IN(–) for correct operation of the AD7710.
Both reference inputs provide a high impedance, dynamic load
similar to the analog inputs. The maximum dc input leakage cur-
rent is 10 pA ( 1 nA over temperature), and source resistance may
result in gain errors on the part. The reference inputs look like the
analog input (see Figure 7). In this case, R
varies with gain. The input sample rate is f
vary with gain. For gains of 1 to 8, C
it is 10 pF; for a gain of 32, it is 5 pF; for a gain of 64, it is 2.5 pF;
and for a gain of 128, it is 1.25 pF.
The digital filter of the AD7710 removes noise from the reference
input just as it does with the analog input, and the same limita-
tions apply regarding lack of noise rejection at integer multiples
of the sampling frequency. The output noise performance
SS
limits, and the V
REF
of 2.5 V, the analog input range on the AIN(+)
REF
BIAS
of 2.5 V, the input voltage range on the
input voltage range limits are obeyed.
REF
REF
INT
voltage down to 1 V but
(REF IN(+) – REF IN(–)),
is 20 pF; for a gain of 16,
INT
CLK IN
is 5 k typ and C
/256 and does not
SS
to AV
DD
and
DD
.
INT
–16–
outlined in Tables I and II assumes a clean reference. If the
reference noise in the bandwidth of interest is excessive, it can
degrade the performance of the AD7710. Using the on-chip
reference as the reference source for the part (that is, connecting
REF OUT to REF IN) results in degraded output noise perfor-
mance from the AD7710 for portions of the noise table that are
dominated by the device noise. The on-chip reference noise
effect is eliminated in ratiometric applications where the refer-
ence is used to provide the excitation voltage for the analog
front end. The connection scheme, shown in Figure 8, is recom-
mended when using the on-chip reference. Recommended refer-
ence voltage sources for the AD7710 include the AD580 and
AD680 2.5 V references.
V
The V
circuitry is biased. It essentially provides the return path for
analog currents flowing in the modulator and, as such, it should
be driven from a low impedance point to minimize errors.
For maximum internal headroom, the V
set halfway between AV
AV
headroom the circuit has at the upper end, while the difference
between V
of headroom the circuit has at the lower end. When choosing a
V
single 5 V operation, the selected V
V
V
AV
tion, the selected V
V
itself is greater than V
example, with AV
allowable range for the V
With AV
V
and V
The V
rejection performance of the AD7710. If the V
the AV
the AV
Zener diode, connected between the AV
source for the V
power supply rejection performance.
BIAS
BIAS
BIAS
BIAS
REF
BIAS
DD
DD
does not exceed AV
is 4.25 V to 5.25 V. With AV
voltage, ensure that it stays within prescribed limits. For
voltage itself is greater than V
Input
REF
BIAS
BIAS
and (V
– 2.1 V. For single 10 V operation or dual 5 V opera-
DD
DD
0.85
DD
= +2.5 V, the V
voltage does have an effect on the AV
supply, it improves the power supply rejection from
SS
input determines at what voltage the internal analog
supply line from 80 dB to 95 dB. Using an external
Figure 8. REF OUT/REF IN Connection
= 9.5 V, V
and (V
BIAS
V
BIAS
REF
REF OUT
+ 0.85
DD
BIAS
AD7710
BIAS
voltage gives the improvement in AV
does not exceed AV
= 4.75 V, V
SS
SS
voltage must ensure that V
DD
– 0.85
BIAS
= 0 V, and V
+ 3 V or less than AV
BIAS
DD
V
and V
REF
voltage is 2.125 V to 2.625 V.
or V
range is –2.625 V to +2.625 V.
) determines the amount of
REF IN (+)
REF IN (–)
V
SS
SS
DD
SS
REF
. The difference between
BIAS
SS
= 0 V, and V
, or that the V
= +4.75 V, V
) determines the amount
+ 2.1 V and less than
REF
voltage must ensure that
BIAS
DD
DD
= 5 V, the range for
line and V
or V
voltage should be
DD
BIAS
SS
DD
REF
power supply
SS
BIAS
or that the
BIAS
voltage tracks
–3 V. For
= –4.75 V,
= 2.5 V, the
BIAS
voltage
REV. G
0.85
DD
, as the