ucb1300 NXP Semiconductors, ucb1300 Datasheet - Page 36

• Manufacturer Part Number: ucb1300
• Description: Advanced Modem/audio Analog Front-end
• Manufacturer: NXP Semiconductors

Philips Semiconductors
APPLICATION INFORMATION
In this chapter some application information is provided. Additional information is also available in the following
application notes (available at www.philips.semiconductors.com)
Sidetone suppression circuit
An important built-in feature of the telecom codec is the sidetone suppression circuit. The sidetone suppression circuit is
activated when TEL_SIDE_ENA in the telecom control register B is set. The telecom input signal contains a large part
of the telecom output signal, when the sidetone suppression circuit is disabled. The available dynamic range of the
telecom input is occupied largely by the telecom output voltage.
The sidetone suppression circuit subtracts a part of the telecom output signal from the telecom input signal when
activated. In that case, the available dynamic range is used more effectively than without sidetone suppression.
The built-in side tone suppression circuit, shown in Fig.31, has a fixed subtraction ratio, set be the resistors R
which equals 600/456. This ratio is calculated from the following relations:
2000 Jun 26
AN807: UCB1300 audio codec
AN809: Differences between UCB1300 and UCB1200
AN810: DAA printed circuit board layout
AN812: Data access arrangement (DAA)
Advanced modem/audio analog front-end
A
B
1:1 transformer
Fig.31 Typical telecom codec sidetone suppression circuit (without protection circuits).
Rt
Rt
Rt
Rt
TOUTP
TOUTN
TINP
TINN
11
15
14
12
UCB1300
36
Ri
Rs
Rs
Ri
-
+
+
-
Rg
Rg
Product specification
UCB1300
s
and R
i
,