as2525 austriamicrosystems, as2525 Datasheet - Page 11

• Manufacturer Part Number: as2525
• Description: Single Chip Handsfree Phone Cmos Integrated Circuit
• Manufacturer: austriamicrosystems

Datasheet AS2525
Table 13: Handset Rx soft clipping selection
There is LLC option for this path.
The gain of the LS —> LO1/LO2 receive path is set to 29
dB.
This gain can be changed by set-up programming from 22
dB to -37 dB in 1 dB steps.
Table 14: Loudspeaker gain setting
The user can also change the gain using the [V+]/[V-] keys
(see section "Handsfree"). The volume range is 20 dB (8
steps, each 2.5 dB).
The receive input is the differential signal of RI and STB.
The soft clip circuit limits the output voltage swing at
LO1/LO2 to 1 V
Table 15: Loudspeaker soft clipping selection
There is optional LLC for this path.
Line Loss Compensation (LLC)
The line loss compensation is set-up programmable and
effects only the handset mode.
Revision 2.1
Digit
Digit
Key
[PG] + [0] + (Password) + [9] + [3] + (digit) + [PG
[PG] + [0] + (Password) + [#] + [5] + (digit) + [PG]
[0]
[1]
(x)
[0]
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[0]
[1]
[PG] + [0] + (Password) + [0] + [4] + (x) + [PG]
Handset Rx Soft Clipping (Earpiece)
Disabled
Enabled
Handsfree Rx Soft Clipping (Loudspeaker)
Disabled
Enabled
Rx Gain (dB)
LS to LO1/2
PEAK
.
22
23
24
25
26
27
28
29
[M1]
[M2]
[M3]
[M4]
[M5]
[M6]
Key
(x)
[8]
[9]
Rx Gain (dB)
LS to LO1/2
30
31
32
33
34
35
36
37
]
Table 16: Line loss compensation selection
When it is activated, the transmit and receive gains for
both channels are decreased by 6 dB at line currents from
20 mA to 50 mA or from 45 mA to 75 mA depending on
selected range.
Handsfree
The handsfree function allows voice communication without
using the handset (full 2-way speaker phone). Two voice
controlled attenuators prevent acoustic coupling between
the loudspeaker and the handsfree microphone.
The voice switching circuit has three states, namely idle,
transmit or receive. In receive mode the attenuation of the
receive path and the transmit path can be controlled by the
volume keys between 0 dB and -20 dB. The following table
(Table 18: Handsfree attenuation scheme) shows how
voice switching is controlled.
A background monitoring circuit is incorporated. This
circuit can be enabled/disabled as required
Table 17: Background noise monitoring selection
voice switching circuit
Digit
Digit
[PG] + [0] + (Password) + [#] + [6] + (digit) + [PG]
[PG] + [0] + (Password) + [0] + [5] + (digit) + [PG]
[0]
[1]
[2]
[0]
[1]
TX_atten
RX
Figure 6: Handsfree voice switching
LLC Range
No LLC (gain independent of line current)
-1 dB/5 mA from 20 to 50 mA
-1 dB/5 mA from 45 to 75 mA
Background Noise Monitoring
Disabled
Enabled
switching
Voice
austriamicrosystems
speech
Backgnd
monitor
noise
.
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