BASS BOOST FUNCTION

The Bass Boost Function can be toggled by changing the

logic at pin 19. A logic low will switch the power amplifiers to

bass boost mode. In bass boost mode the low frequency

gain of the amplifier is set by the external capacitor.

Whereas a logic high sets the amplifiers to unity gain.

In some cases a designer may want to improve the low fre-

quency response of the bridged amplifier or incorporate a

bass boost feature. This bass boost can be useful in systems

where speakers are housed in small enclosures. If the de-

signer wishes to disable the bass boost feature, pin 19 can

be tied to V

When bass boost is enabled, the output amplifiers will be in-

ternally set at a gain of 2 at low frequencies (gain of 4 in

bridged mode). As shown in Figure 2, C

frequency for the bass boost. At low frequencies the capaci-

tor will be virtually an open circuit. At high frequencies the ca-

pacitor will be virtually a short circuit. As a result of this, the

gain of the bridge amplifier is increased at low frequencies. A

first order pole is formed with a corner frequency at:

f

The resulting low frequency differential gain of this bridged

amplifier becomes:

2(10k

Ω +10kΩ) /10kΩ =4

With C

frequency of 160 Hz. The low frequency boost formulas as-

sume that C

quency response as explained in the Proper Selection of

External Components section. See the Typical Perfor-

mance Characteristics section for a graph that includes

bass boost performance with various values of C

DC VOLUME CONTROL

The DC voltage at the DC Volume Control pin (pin 5) deter-

mines the attenuation of output of the amplifiers. If the DC

potential of pin 5 is above 4V (typical 80% V

amplifiers are set at unity gain. The attenuator range is from

0dB(pin5=80% V

age greater than 4V (or 80% V

unity. Refer to the Typical Performance Characteristics for

detailed information of the attenuation characteristics of the

DC Volume Control pin.

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