µ
PD9930
2.1.3 Audio Analog Output
Includes receiver output and accessory output. Sidetone addition is also possible.
(1) Post filter 2 (receiver amplifier 1)
This circuit adjusts the gain of D/A differential output signal (volume control), and then converts it to single output
signal.
(2) Receiver drive amplifier (receiver amplifier 2)
This is differential output amplifier that can directly drive a piezo-electric receiver (when using a dynamic receiver,
an additional external amplifier is necessary). The sidetone is added in this circuit.
(3) Post filter 1 (accessory output amplifier)
This circuit converts D/A differential output signal to single output signal. Connected to the earphone of the head
set (capacitance load), etc.
Table 2-2 Analog Output Functions
Amplifier
Function
Gain setting method
Gain setting range
Receiver Amplifier 1
Microcontroller command
0 to –31 dB (1 dB steps)
Receiver Amplifier 2
External resistor
Voice receive signal gain:
–
∞
to + 10 dB
20 log R3 (dB) + 6 dB
Note
R2
Sidetone signal gain:
–
∞
to + 3 dB
R3
20 log
(dB) + 6 dB
Note
R1
Accessory Output Amplifier
—
—
Minimum resistive load
Maximum capacitive load
Maximum output level
100 kΩ
20 pF
0.6 V
0-p
2 kΩ
60 nF
4 V
p-p
(Differential output)
100 kΩ
100 pF
0.6 V
0-p
Note
Conversion result (single output
→
differential output)
Figure 2-2 Analog Output Block
RAUXO
Post filter 1
(accessory output
amplifier)
0 dB fix
Post filter 2
(receive amplifier 1)
0 to –31 dB
(1 dB steps)
Receiver drive amplifier
(receiver amplifier 2)
–
+
REC1O
R2
Sidetone signal
R1
R3
REC2I–
REC2O–
to V
ref
REC2O+
–
+
to V
ref
10
NEC [ NEC ]
