µ
PD9930
2. BLOCK FUNCTIONS
2.1 CODEC
2.1.1 Audio Codec
Audio analog signal and linear code conversion.
• Input/output format: 16 bits (2's complement)
• Accuracy: 13 bits
2.1.2 Audio Analog Input
Includes microphone input and accessory input.
(1) Microphone amplifier
Amplifiers differential input signals from the microphone to the required gain.
(2) Accessory input amplifier
Amplifiers the accessory input signal to the required gain.
(3) Pre-filter + mixer
Selects the output signal of microphone amplifier and accessory input amplifier, and inputs these to A/D converter
after controlled gain.
Table 2-1 Analog Input Function
Amplifier
Function
Gain setting method
Gain setting range
Microphone Amplifier
External resistor
15 to 33 dB
R2
20 log
(dB)
R1
50 kΩ
(Including gain setting resistance)
20 pF
0.6 V
0-p
Accessory Input Amplifier
External resistor
0 to 10 dB
R3
20 log
(dB)
R4
300 kΩ
(Including gain setting resistance)
20 pF
0.6 V
0-p
Pre-filter + Mixer
Microcontroller
command
0 or –3 dB
Minimum resistive load
Maximum capacitive load
Maximum output level
—
—
—
Figure 2-1 Analog Input Block
MIXI
MICO
(15 to 33 dB)
R2
R1
R1
(to XACOMO)
(0 to 10 dB)
R3
R4
to V
ref
XAUXO
XAUXI–
–
+
MICI–
MICI+
Microphone
amplifier
–
+
Pre-filter +
mixer
0 or –3 dB
Accessory input amplifier
9
NEC [ NEC ]
