EUA6011AQIR1 데이터 시트보기 (PDF) - Eutech Microelectronics Inc

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EUA6011AQIR1

3-W Stereo Audio Power Amplifier with Advanced DC Volume Control

Eutech Microelectronics Inc 

the part is in the fade-off mode. The gain is set to the

highest level, and the output is at VDD when the

amplifier is shut down.

The power-up sequence is different from the shutdown

sequence and the voltage on the pin does not change the

power-up sequence. Upon a power-up condition, the

EUA6011A begins in the lowest gain setting and steps

up 2 dB every 2 clock cycles until the final value is

reached as determined by the dc voltage applied to the

VOLUME, SEDIFF , and SEMAX pins.

Bridged-Tied Load Versus Single-Ended Mode

Figure 28 show a Class-AB audio power amplifier (APA)

in a BTL configuration. The EUA6011A BTL amplifier

consists of two Class-AB amplifiers driving both ends of

the load. There are several potential benefits to this

differential drive configuration, but initially consider

power to the load. The differential drive to the speaker

means that as one side is slewing up, the other side is

slewing down, and vice versa. This in effect doubles the

voltage swing on the load as compared to a ground

referenced load. Plugging 2×VO(PP) into the power

equation, where voltage is squared, yields 4× the output

power from the same supply rail and load impedance(see

equation 1)

V(rms) = VO(PP)

Power = V(rms) 2 ------(1)

22

RL

EUA6011A

is due to the high pass filter network created with the

speaker impedance and the coupling capacitance and is

calculated with equation 2.

1

fC =

----------------------------------(2)

2π RLCC

For example, a 68µF capacitor with an 8-Ω speaker would

attenuate low frequencies below 293 Hz. The BTL

configuration cancels the dc offsets, which eliminates the

need for the blocking capacitors. Low-frequency

performance is then limited only by the input network and

speaker response. Cost and PCB space are also minimized

by eliminating the bulky coupling capacitor.

Figure 29. Single-Ended configuration and

Frequency Response

Increasing power to the load does carry a penalty of

increased internal power dissipation. The increased

dissipation is understandable considering that the BTL

configuration produces 4 × the output power of the SE

configuration. Internal dissipation versus output power is

discussed further in the crest factor and thermal

considerations section.

Figure 28.Bridge-Tied Load configuration

Single-Ended Operation

In SE mode the load is driven from the primary amplifier

output for each channel (OUT+, terminals 21 and 4 ). The

amplifier switches single-ended operation when the

SE/BTL terminal is held high. This puts the negative

outputs in a high-impedance state, and reduces the

amplifier’s gain to 1V/V.

In a typical computer sound channel operating at 5V,

bridging raises the power into an 8-Ω speaker from a

singled-ended (SE, ground reference) limit of 250 mW to

1W. In sound power that is a 6-dB improvement, which is

loudness that can be heard. In addition to increased power

there are frequency response concerns. Consider the

single-supply SE configuration shown in Figure 29.

A coupling capacitor is required to block the dc offset

voltage from reaching the load. These capacitors can be

quite large (approximately 33µF to 1000µF) so they tend

to be expensive, heavy, occupy valuable PCB area, and

have the additional drawback of limiting low-frequency

performance of the system. This frequency limiting effect

Input MUX Operation

The input MUX allows two separate inputs to be applied

to the amplifier. This allow the designer to choose which

input is active independent of the state of the

SE/BTL terminal. When the HP/LINE terminal is held

high, the headphone inputs are active. When the

HP/LINE terminal is held low, the line BTL inputs are

active.

DS6011A Ver 1.0 Mar. 2006

16

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