1

4

8

1m

10m

100m

1

6

0.01

0.1

1.0

10

No Clip

Enabled

No Clip

Disabled

2

0

1

3

4

7

0

0.2

0.4

0.6

1.0

2

5

0.8

6

Voltage Limiter off

ALC max attenuation

TI Confidential - NDA Restrictions

LM49151

SNAS482F – MARCH 2009 – REVISED MARCH 2013

www.ti.com

Figure 57. Voltage Limiter Function

Figure 58. No Clip Function

Blue, Green = Output Power vs Input Voltage

Gray, Yellow = THD+N vs Input Voltage

When No Clip is enabled, class D speaker output reduces when it’s about to enter clipping region and power stay

3.3V, there is a 6 dB of headroom for the change in input. Please see the ALC typical performance curves for

additional plots relating to different supply voltages and LS_GAIN settings for specific application parameters.

ATTACK TIME

exceeds the ALC threshold. Fast attack times allow the ALC to react quickly and prevent transients such as

symbol crashes from being distorted. However, fast attack times can lead to volume pumping, where the gain

reduction and release becomes noticeable, as the ALC cycles quickly. Slower attack times cause the ALC to

ignore the fast transients, and instead act upon longer, louder passages. Selecting an attack time that is too slow

can lead to increased distortion in the case of the No Clip function, and possible output overload conditions in the

coefficient as given by Equation 2:

(2)

Where

Table 7). The attack time coefficient allows the user to set a nominal attack time. The internal 20k

Ω resistor is

subject to temperature change, and it has tolerance between -11% to +20%.

28

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