la2806m Sanyo Semiconductor Corporation, la2806m Datasheet - Page 6

• Manufacturer Part Number: la2806m
• Description: Signal Processor And Power Amplifier Ic For Telephone Answering Machines
• Manufacturer: Sanyo Semiconductor Corporation

IC Usage Notes
1)
2)
3)
4)
5)
6)
7)
Control Inputs (pin 26 to 30)
Each control input is connected to V
Automatic Level Control (ALC)
The automatic level control circuit operates when the input signal is in the range between –64 dBV to –20 dBV. The output
saturation level is 500 mV rms.
Mute Circuit (pin 24)
The VOX. C/MUTE input controls the mute function.
When it goes HIGH, analog switch SW5 opens, switching off the power amplifier. The power amplifier output goes high
impedance and VOX (pin 25) goes LOW.
V/I Conversion
V/I conversion is performed in order to extract the recording current for DC bias. The conversion gain and the bias current
can be controlled by an external resistor connected to pin 1, and current that is equal to the pin 1 output current is output on
pin 2.
Playback Amplifier and Preamplifier Feedback Resistance
As the playback amplifier and preamplifier employ a zero-bias method, the amplifier’s output DC level (V
by the feedback resistance (R
A feedback resistance of 100 k
DC level with sufficient output dynamic range.
Filter amplifier
A bandwidth-limiting filter is provided to restrict the VOX circuit input frequency. It can also be used as an inverting
amplifier. It has a center frequency of 800 Hz, a gain of 2 and a Q factor of 1.
Voice-operated Switch (VOX)
This switch detects whether anyone is speaking or not by detecting the level of the signal (V13) on the filter amplifier output
pin (pin 13).
V13 % –18 dBV ... Pin 25 low
The detection level is adjusted by inserting resistor R between TH (pin 23) and V
Refer to the diagram below.
V
ODC
= V
BE
+ R
NF
Ii
NF
) and the NF pin sink current (Ii = 15 µA).
is recommended for both the playback amplifier and the preamplifier to provide an output
REF
V
through a 100 k
BE
6 0.7 V
LA2806M
resistance. The control input threshold level is V
Unit (resistance:
REF
(pin 14).
, capacitance: F)
ODC
REF
No. 3852 - 6/11
) is determined
3/5.