AS2536 austriamicrosystems, AS2536 Datasheet - Page 6

• Manufacturer Part Number: AS2536
• Description: IC MULTI-STANDARD CMOS TELEPHONE SOIC-28
• Manufacturer: austriamicrosystems

Specifications of AS2536

• Audio Control Type: Volume
• Control / Process Application: Electronic Telephonic Set
• Supply Voltage Range: 3.8V To 5V
• Operating Temperature Range: -25°C To +70°C
• Audio Ic Case Style: SOIC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Data Sheet AS2533-36
Transmit
The gain of the transmit path is 37 dB for 600 Ω line
termination from M1/M2 to LS (see test circuit Figure 9).
The microphone input is differential with an input
impedance of 20 kΩ.
The soft clip circuit limits the output voltage at LI to 2V
(see Figure 11). The attack time is 30 μs/6 dB and the
decay time is 20 ms/6 dB. When mute is active, during
dialing or after pressing the P/M key, the gain reduced by >
60 dB.
Receive
The gain of the receive path is 3 dB for 600 Ω line
termination (test circuit Figure 9). The receive input the
differential signal of RI and STB. When mute is active
during dialing the gain is reduced by > 60 dB. During
DTMF dialing a MF comfort tone is applied to the receiver.
The comfort tone is the DTMF signal with level that is -30
dB relative to the line signal.
The receive gain can be changed by pressing the volume
keys. The VOL key gives a +5.4 dB boost and has a toggle
function, i.e. repressing the key resets the gain to default.
As an alternative the +/– keys can be used. The + key
increases the gain by 8.1 dB in 3 steps and the – key
decreases the gain by 5.4 dB in 2 steps (total range 13.5
dB). On AS2533/35 the volume is reset to default by next
off-hook and on AS2534/36 the volume setting will remain
at last setting. A POR will always reset the volume to
default.
The soft clip circuit limits the voltage at the receive output
(RO) to 1V
distortion and acoustic shock.
Sidetone
A good sidetone cancellation is achieved by using the
following equation:
The sidetone cancellation signal is applied to the STB
input.
Revision 8.8
Z
LI
PEAK
(see Figure 10). It prevents harsh
Figure 5 Side Tone Balance
Z
BA
Z
Z
Line
BAL
=
Z
Z
2
1
Z
Z
1
2
PEAK
Line Loss Compensation
The line loss compensation is a pin option. When it is
activated, the transmit and receive gains are decreased by
6 dB at line currents from 20 to 50 mA when LLC = A
and 45 to 75 mA when LLC = high (@ R1 = 30 Ω). The line
loss compensation is disabled when LLC = low (see Figure
6 and Figure 7).
Dialing Functions
Valid Keys
The key scanning is enabled when HS/DPN is pulled high
and V
keyboard by connecting the appropriate row to the column
(R
matrix with single contacts. Four diodes are used to extend
the number of rows (see keyboard arrangement fig. 2). It is
also possible to connect a microcontroller to the rows and
columns (see application note AN3010).
P/M and MT Key
The P/M key is used to enter the Program/Mute state.
Depressing the P/M key mutes the speech circuit and the
device is in program state. Repressing the P/M key
deactivates the mute and program state (toggle
function).The MT key works in similar way, but has no
program function.
When program/mute is activated, the LED indication is
turned on (flashing: 80 ms 'on' and 1 sec 'off').
Dial Mode Selection
The default mode (LD or MF) can be selected by the mode
pin. When default LD mode is selected, a temporary
change to MF can be invoked by pressing T/P key (not
AS2535) or the * key (when mode pin = row 5, the MF tone
is generated with the first * key entry). The circuit will
revert to LD by repression the T/P key (not AS2535) or by
pressing the R (R1, R2 or R3) key or by next on-hook.
When MF mode is selected by the mode pin, the circuit can
not be changed temporary to LD but will remain in MF
mode.
Centrex Keys (not AS2535)
The alphanumeric keys accommodate easy use of centrex
services. The A, B, C and D keys are only valid in MF
mode (including temporary MF) and are not storable.
Pressing one of these keys will invoke the appropriate
MF tones to be transmitted.
The centrex keys are not stored in the RAM, and
subsequently entered digits are buffered in FIFO.
ON
< 1 kΩ). This can be done using an n x m keyboard
DD
is above V
REF
. A valid key is detected from the
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GND