AD7742BR-REEL7 Analog Devices Inc, AD7742BR-REEL7 Datasheet - Page 8

• Manufacturer Part Number: AD7742BR-REEL7
• Manufacturer: Analog Devices Inc

Specifications of AD7742BR-REEL7

• Converter Function: VFC
• Full Scale Frequency: 2750
• Power Supply Requirement: Single
• Single Supply Voltage (typ): 5V
• Single Supply Voltage (max): 5.25V
• Single Supply Voltage (min): 4.75V
• Dual Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Package Type: SOIC N
• Lead Free Status / Rohs Status: Not Compliant

AD7741/AD7742
UNI/BIP
N/A
0
0
1
1
As can be seen from Table II, the AD7741 has one input range
configuration whereas the AD7742 has unipolar/bipolar as
well as gain options depending on the status of the GAIN
and UNI/BIP pins.
The transfer function for the AD7741 is shown in Figure 3.
Figure 4 shows the AD7742 transfer function for unipolar input
range configuration while the AD7742 transfer function for
bipolar input range configuration is shown in Figure 5.
Figure 3. AD7741 Transfer Characteristic for Input Range
from 0 to V
Figure 4. AD7742 Transfer Characteristic for Unipolar
Differential Input Range: 0 V to V
common-mode range must be between +0.5 V and
V
DD
FREQUENCY
(0.05 f
(0.45 f
– 1.75 V. UNI/ BIP pin tied to V
FREQUENCY
(0.05 f
OUTPUT
f
f
(0.45 f
OUT
OUT
OUTPUT
f
f
f
OUT
OUT
OUT
f
CLKIN
MIN
OUT
MAX
CLKIN
CLKIN
MIN
MAX
CLKIN
REF
)
)
)
)
0
0
GAIN
N/A
0
1
0
1
+
GAIN
V
REFIN
REF
Gain, G
X1
X1
X2
X1
X2
DD
REF
.
/Gain; the input
Table II. AD7741/AD7742 Input Range Selection
INPUT VOLTAGE
DIFFERENTIAL
VOLTAGE V
INPUT
IN
V
f
0
–V
–V
0
0
OUT
IN
REF
REF
(Min)
= 0.05 f
/2
–8–
VFC Modulator
The analog input signal to the AD7741/AD7742 is continu-
ously sampled by a switched capacitor modulator whose sam-
pling rate is set by a master clock input that may be supplied
externally or by a crystal-controlled on-chip clock oscillator.
However, the input signal is buffered on-chip before being ap-
plied to the sampling capacitor of the modulator. This isolates
the sampling capacitor charging currents from the analog input
pins.
This system is a negative feedback loop that tries to keep the net
charge on the integrator capacitor at zero, by balancing charge
injected by the input voltage with charge injected by the V
The output of the comparator provides the digital input for the
1-bit DAC, so that the system functions as a negative feedback
loop that tries to minimize the difference signal (see Figure 6).
CLKIN
Figure 5. AD7742 Transfer Characteristic for Bipolar
Differential Input Range: –V
common-mode range must be between +0.5 V and
V
DD
INPUT
– 1.75 V. UNI/ BIP pin tied to GND.
Figure 6. AD7741/AD7742 Modulator Loop
–
+
–
GAIN
V
FREQUENCY
REF
(0.45 f
OUTPUT
f
OUT
f
INTEGRATOR
OUT
MAX
CLKIN
V
f
+V
+V
+V
+V
+V
OUT
IN
)
REF
REF
REF
REF
REF
(Max)
+V
–V
(0.05 f
= 0.45 f
REF
REF
f
/2
/2
OUT
COMPARATOR
REF
CLKIN
MIN
+
/Gain to +V
CLKIN
GAIN
)
V
REF
+
–
CLK
INPUT VOLTAGE
DIFFERENTIAL
REF
/Gain; the
STREAM
1-BIT
Part
AD7741
AD7742
AD7742
AD7742
AD7742
REV. 0
REF
.