Rainbow Electronics ISD5216 - Manual (Page 40)

I5216 SERIES
Advanced Information
PRELIMINARY
Publication Release Date: November 30, 2001
- 40 Revision A1
MICROPHONE INPUTs
The microphone inputs transfer the voice signal to the on-chip AGC preamplifier, or directly to the
CODEC INPUT MUX, depending on the selected path. The AGC circuit has a range of 45 dB in order
to deliver a nominal 694 mV p-p into the storage array from a typical electret microphone output of 2 to
20 mV p-p. The input impedance is typically 10kΩ.
The MICBS pin provides a 2.2V bias voltage for the external microphone only when the AGC is
powered up. Using this regulated bias voltage results in less supply noise coupling into the MIC+ and
MIC- pins compared to the situation in which the external microphone is powered up through the power
supply. It also saves current during power down.
The ACAP pin provides the capacitor connection for setting the parameters of the microphone AGC
circuit. It should have a 4.7 µF capacitor connected to ground. It cannot be left floating. This is because
the capacitor is also used in the playback mode for the AutoMute circuit or when signal compression is
chosen (AMT0 set). The AutoMute circuit reduces the amount of noise present in the output during
quiet pauses. Tying the ACAP pin to ground gives maximum gain. Tying it to VCCA gives minimum
gain for the AGC amplifier, but cancels the AutoMute function.
CDI1 CDI0 CODEC ADC
INPUT
0 0 INP
0 1 SUM2
1 0 MIC
1 1 No Input
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
CIG2 CIG1 CIG0 AXG1 AXG0 AXPD INS0 OSPD AMT0 CDI1 CDI0 OPS1 OPS0 OPA1 OPA0 VLPD CFG0
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
VLS1 VLS0 VOL2 VOL1 VOL0 S1S1 S1S0 S1M1 S1M0 S2M1 S2M0 FLS0 FLD1 FLD0 FLPD AGPD CFG1
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
X X X CKD2 COG2 COG1 COG0 CKDV MUTE HPF0 HSR0 I2S0 LAW1 LAW0 DAPD ADPD CFG2
AGPD CONDITION
0 Power Up
1 Power Down
MIC IN
AGC
MIC+
MIC -
AGCCAP
MICROPHONE
MIC IN
1
(AGPD)
2.2V Voltage
reference
MICBS
CDI0
(
2
CDI1
1 (AGPD)
CODEC INPUT MUX
IN
P
IN
P+
SU
M2
SU
M2
+
CODEC ADC IN
AGC
MIC+
MIC -
AGCCAP
MICROPHONE
MIC IN
11
(AGPD)
2.2V Voltage
reference
MICBS
CDI0
(
2
CDI1
11 (AGPD)
CODEC INPUT MUX
IN
P
IN
P+
SU
M2
SU
M2
+
SU
M2
SU
M2
+