uaa2062 NXP Semiconductors, uaa2062 Datasheet - Page 11

• Manufacturer Part Number: uaa2062
• Description: Analog Cordless Telephone Ic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The TX baseband
This section covers the TX audio path from pins MICI to
TXO.
The microphone amplifier is an inverting operational
amplifier whose gain can be set by external resistors. The
input signal at pin MICI and the output signal at pin MOCO
are both AC-coupled. The non-inverting input is connected
to the internal reference voltage VB. External resistors are
used to set the gain and frequency response.
2000 Aug 10
handbook, full pagewidth
handbook, full pagewidth
Analog cordless telephone IC
(dBV)
TXO
MICI
14
10
20
30
40
0
60
microphone
amplifier
MICO
13
50
30
Fig.8 TX baseband schematic diagram.
CMPI
12
Fig.9 Compressor characteristic.
40
compressor
ALC
CCAP
11
30
20
11
The TX baseband has a compressor with the
characteristic shown in Fig.9. The Automatic Level Control
(ALC) provides a ‘soft’ limit to the output signal swing as
the input voltage increases slowly (i.e. a sine wave is
maintained at the output). A hard limiter clamps the
compressor output voltage at 1.26 V (p-p). The ALC and
the hard limiter can be disabled via the microcontroller
interface. The hard limiter is followed by a mute circuit.
The TX gain is digitally programmable in 32 steps of
0.5 dB.
hard limiter
V CMPI = 4 dBV; V TXO = 1.26 V(p-p)
20
(hard limiting signals)
V CMPI = 16 dBV; V TXO = 13 dBV
(slowly changing ALC signals)
TX mute
V TXO = 11.5 dBV
V CMPI = 2.5 dBV
10
CMPI (dBV)
TX gain
0
Product specification
FCA125
TXO
FCA126
6
UAA2062