Texas Instruments TPA0162, Руководство пользователя, Страница: 22 / 36

The TPA0162 Audio Power Amplifier Evaluation Module
3-6 Details
Pushbuttons S2 (UP) and S3 (DOWN) adjust the amount gain in the initial
stage of the amplifier, which could be considered the preamplifier stage. As a
result, the total harmonic distortion (THD) changes very little over all volume
levels. At power up, this gain is set at the lowest level, –85 dB, or mute. Each
time a button is pressed, the volume changes by one increment. If a button is
held in the depressed position, the volume changes by one increment every
four clock cycles, followed by a short delay. This delay decreases the longer
the button is depressed, eventually reaching a delay of zero. Table 3–1 shows
the volume control steps.
Table 3–1. TPA0162 EVM Gain Settings
VOLUME
CONTROL CONTROL
(dB)
20
18
16
14
12
10
8
6
4
2
0
–2
–4
–6
UP
–8
UP
–10 VOLUME
–12
DOWN
–14
DOWN
–16
–18
–20
–22
–24
–26
–28
–30
–32
–34
–36
–38
–40
–85 MUTE (Initial/power up level)