MAS9191AJ MAS [Micro Analog systems], MAS9191AJ Datasheet - Page 19

• Manufacturer Part Number: MAS9191AJ
• Description: Single Chip AMPS/ETACS/NAMPS Audio/Data Processor
• Manufacturer: MAS [Micro Analog systems]

FUNCTION
◆
The TX audio block is in the power down mode after
a reset. The block is set to the operation mode with
the AUDIOP bit of register 07
controls the RX audio block. The TX audio block
starts with switch M2, which is controlled by bits 4
and 5 in register 00
the following blocks as an input source: 1) After a
reset the input source is connected to signal ground.
2) In the second position the input is connected to
the microphone amplifier A6. The gain of amplifier A6
is determined with external components. The
maximum gain is 30 dB. 3) In the third position the
input is connected to EXTMIC, which is for external
accessories. 4) The fourth position selects the DTMF
generator. The DTMF generator is controlled with
registers 05
the low frequencies and register 06
high frequencies. A detailed description of how to
use these registers is in the REGISTERS section.
The DTMF generator is in the power down mode
after a reset and can be set up with the DTMFTP bit
of register 07
The signal is then filtered with anti-aliasing filter F8.
The gain at 1kHz is 0dB and the cutoff frequency is
15kHz. After the filter the signal is amplified with
MIC
MICSGND
MICFB
EXTMIC
TX Audio
HEX
HEX
A6
.
and 06
GC5
Generator
DTMF
HEX
M2
. Switch M2 connects one of
HEX
SYS0
SYS1
F8
. Register 05
HEX
GC3
. The same bit also
LIMITER
HEX
F9LP
HEX
controls the
S15
controls
Audio Transmit Path
F11
SYS0
SYS1
F9HP
S16
GC6
GC3. The gain is
according to bits 0..3 in register 00
signal is then fed to lowpass filter F9LP and highpass
filter F9HP, which are 4th order SC filters. During
normal operation the output of filter F9HP is
connected to output MICOUT. With switch SYS0-
SYS1 the highpass filter can be transferred to the
output of GC5 after the signal has been compressed
and pre-emphasized. Bit 6 in register 12
in register 14
MICOUT
compressor input COMPIN. The MICOUT can also
be used as a source for the side tone amplifier and
for detecting the audio level with the uncommitted Op
Amp (See APPLICATIONS section). The compressor
is an SC audio type with a 2:1 compressing ratio.
The detailed values are found in the ELECTRICAL
CHARACTERISTICS section under Compressor.
The compressor can be bypassed internally with
switch S12 or externally with S13. The bypass gain is
0dB (100 mV
external 22nF capacitor between pins CAMP20 and
CWCIN. Another 22nF capacitor is needed between
pins CAMP2IN and COUT. This capacitor also
serves as an external DC blocking capacitor between
the compressor output and gain control GC4 input.
SYS0
SYS1
GC7
S7
COMPRESSOR
TXTST
through
TX data, ST
HEX
2:1
rms
control switch SYS0-SYS1. Connect
). The compressor requires one
S12
S19
a
-3dB...+3dB with 16 steps
F13
22nF
S13
S20
+
GC4
capacitor
HEX
GC9
PRE-EMPHASIS
DA9191A.000
July 31, 1997
. The amplified
F10
HEX
F14
and bit 6
to
S14
the
TX
19