AD73322LAR-REEL Analog Devices Inc, AD73322LAR-REEL Datasheet - Page 34

• Manufacturer Part Number: AD73322LAR-REEL
• Description: IC ANALOG FRONT END DUAL 28-SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD73322LAR-REEL

• Rohs Status: RoHS non-compliant
• Number Of Bits: 16
• Number Of Channels: 4
• Power (watts): 73mW
• Voltage - Supply, Analog: 2.7 V ~ 5.5 V
• Voltage - Supply, Digital: 2.7 V ~ 5.5 V
• Package / Case: 28-SOIC (7.5mm Width)
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 3.3V
• Package Type: SOIC W
• Lead Free Status / RoHS Status: Not Compliant

AD73322L
INTERFACING TO AN ELECTRET MICROPHONE
Figure 39 details an interface for an electret microphone which
may be used in some voice applications. Electret microphones
typically feature a FET amplifier whose output is accessed on
the same lead which supplies power to the microphone;
therefore, this output signal must be capacitively coupled to
remove the power supply (dc) component. In this circuit, the
AD73322L input channel is being used in single-ended mode
where the internal inverting amplifier provides suitable gain to
scale the input signal relative to the ADC’s full-scale input
range. The buffered internal reference level at REFOUT is used
via an external buffer to provide power to the electret
microphone. This provides a quiet, stable supply for the
microphone. If this is not a concern, then the microphone can
be powered from the system power supply.
ANALOG OUTPUT
The AD73322L’s differential analog output (VOUT) is produced
by an on-chip differential amplifier. The differential output can
be ac-coupled or dc-coupled directly to a load which can be a
headset or the input of an external amplifier (the specified
minimum resistive load on the output section is 150 Ω.) It is
possible to connect the outputs in either a differential or a
single-ended configuration, but please note that the effective
maximum output voltage swing (peak to peak) is halved in the
case of single-ended connection. Figure 40 shows a simple
circuit providing a differential output with ac coupling. The
capacitors in this circuit (C
can be chosen as follows:
where f
10µF
C
OUT
R
5V
A
R
B
C
=
= desired cutoff frequency.
C2
ELECTRICITY
PROBE
2
R1
π
Figure 39. Electret Microphone Interface Circuit
fc
100pF
50kΩ
1
R
LOAD
VOUTP1
REFOUT
REFCAP
VOUTN1
C
VFBN1
VFBP1
VINN1
VINP1
REFCAP
V
REF
OUT
) are optional; if used, their value
+6/–15dB
PGA
REFERENCE
GAIN
CONTINUOUS
±1
LOW-PASS
FILTER
TIME
AD73322L
V
REF
0/38dB
PGA
Rev. A | Page 34 of 48
Figure 41 shows an example circuit for providing a single-ended
output with ac coupling. The capacitor of this circuit (C
not optional if dc current drain is to be avoided.
R
R
LOAD
LOAD
Figure 41. Example Circuit for Single-Ended Output
Figure 40. Example Circuit for Differential Output
C
C
C
C
REFCAP
OUT
OUT
OUT
0.1µF
VOUTN1
REFOUT
REFCAP
VOUTN1
REFOUT
REFCAP
VOUTP1
VOUTP1
VFBN1
VFBP1
VFBN1
VFBP1
VINN1
VINN1
VINP1
VINP1
V
V
REF
REF
+6/–15dB
+6/–15dB
PGA
PGA
REFERENCE
REFERENCE
GAIN
GAIN
CONTINUOUS
CONTINUOUS
±1
±1
LOW-PASS
LOW-PASS
FILTER
FILTER
TIME
TIME
AD73322L
AD73322L
OUT
) is