EUA5202 datasheet(21/23 Pages) EUTECH

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EUA5202

DS5202 Ver 1.6 May. 2005

Input MUX Operation

Working in concert with the

BTL

SE/

feature, the

LINE

HP/

MUX feature gives the audio designer the

flexibility of a multichip design in a single IC (see

Figure 58). The primary function of the MUX is to allow

different gain settings for BTL versus SE mode.

Speakers typically require approximately a factor of 10

more gain for similar volume listening levels as

compared to headphones. To achieve headphone and

speaker listening parity, the resistor values would need

to be set as follows:

-------------------------- (11)

If, for example RI (HP) = 10 kΩ and RF (HP) = 10kΩ then

SE Gain (HP) = -1

















−

(LINE)

Gain

BTL

-------------------- (12)

If, for example RI (LINE) = 10kΩ and RF (LINE) = 50kΩ then

BTL Gain (LINE) = -10

Another advantage of using the MUX feature is setting

the gain of the headphone channel to -1. This provides

the optimum distortion performance into the headphones

where clear sound is more important. Refer to the

BTL

SE/

operation section for a description of the

headphone hack control circuit.

BTL

SE/

Operation

The ability of the EUA5202 to easily switch between

BTL and SE modes is one of its most important cost

saving features. This feature eliminates the requirement

for an additional headphone amplifier in applications

where internal stereo speakers are driven in BTL mode

but

external

headphone

speakers

must

accommodated. Internal to the EUA5202, two separate

amplifiers drive LOUT- and ROUT- (terminals 10 and

15).When

BTL

SE/

is held high, the OUT- amplifier

are in high output impedance state, which configures the

EUA5202 as an SE driver from LOUT + and ROUT +

(terminal 3 and 22). IDD is reduced by approximately

one-half in SE mode. Control of the

BTL

SE/

input can

be from a logic-level CMOS source, or, more typically,

from a resistor divider network as shown in Figure 59.

Using a readily available 1/8-in. (3.5mm) stereo

headphone jack, the control switch is closed when no

plug is inserted. When closed the 100-kΩ

/1-kΩ divider

pulls the

BTL

SE/

input low. When a plug is inserted,

the OUT- amplifier is shutdown causing the speaker to

mute (virtually open-circuits the speaker). The OUT+

amplifier then drives through the output capacitor (CO)

into the headphone jack. As shown n the full feature

application (Figure 2), the input MUX control can be

tied to the

BTL

SE/

input. The benefits of doing this are

described in the following input MUX operation section.

Mute and Shutdown Mode

The EUA5202 employs both a mute and a shutdown

mode of operation designed to reduce supply current, IDD,

to the absolute minimum level during periods of nonuse

for battery-power conservation. The SHUTDOWN input

terminal should be held low during normal operation

when the amplifier is in use. Pulling SHUTDOWN high

causes the outputs to mute and the amplifier to enter a

low-current state, IDD = 5 µA. SHUTDOWN or MUTE

IN should never be left unconnected because amplifier

operation would be unpredictable. Mute mode alone

reduces IDD to 1.5 mA.

















−

(HP)

Gain

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