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1 Introduction
Application Report
SLAA260 – September 2005
The Built-In AGC Function in TSC2100/01 and
TLV320AIC26/28/32/33 Devices
Wendy Fang and Nitesh Kekre ............................................................................................ DAP Group
ABSTRACT
Applying the built-in AGC function requires initializing or setting up a group of
corresponding control registers inside the TSC2100/01 and TLV320AIC26/28/32/33
devices. This application report describes how to set up the AGC properly and provides
examples.
Contents
1 Introduction .......................................................................................... 1
2 AGC Variables ...................................................................................... 2
3 AGC Settings and Status .......................................................................... 4
4 Application Examples .............................................................................. 6
5 References .......................................................................................... 7
List of Figures
1 AGC Function ....................................................................................... 2
2 AGC Hysteresis ..................................................................................... 3
List of Tables
1 AGC Variables Description ........................................................................ 2
2 TSC2100 or AIC26 AGC Variable Values and Locations ..................................... 4
3 TSC2101 or AIC28 AGC Variable Values and Locations ..................................... 4
4 AIC32 or AIC33 AGC Variable Values and Locations ......................................... 4
5 AGC Control and Status ........................................................................... 5
One or more automatic gain control (AGC) modules are built into the analog input circuitry of a touch
screen controller (TSC) with audio codec devices, such as the TSC2100 and TSC2101, or an audio codec
device, such as TLV320AIC26 (AIC26 for short) and TLV320AIC33 (or AIC33), to help users to improve
audio recording performance under certain applications and environments.
An AGC is a smart programmable gain amplifier (PGA) in which the input signal, corresponding to its
amplitude or volume, is automatically adjusted in a specified manner. The AGC is useful where the audio
input volume changes dynamically and frequently so that any manual or linear PGA cannot provide proper
gain. As an example, during a teleconference, because some people sit near the microphone and some
farther away, the voice signal to the microphone may be too weak or too strong; thus, any non-automatic
PGA can delivery only poor recording results. An AGC, on the other hand, can automatically adjust the
gain, as shown in Figure 1 (see the Reference section of this application report), so that the signal is
maintained at a certain nominal constant level (called target gain) over a changing range of real-world
conditions.
SLAA260 – September 2005 The Built-In AGC Function in TSC2100/01 and TLV320AIC26/28/32/33 Devices 1
