EUA5202
Input MUX Operation
Operation
SE/BTL
Working in concert with the
feature, the
SE/BTL
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 or speakers must be
accommodated. Internal to the EUA5202, two separate
amplifiers drive LOUT- and ROUT- (terminals 10 and
MUX feature gives the audio designer the
HP/LINE
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:
15).When
is held high, the OUT- amplifier
SE/BTL
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
R
R
F
(HP)
-------------------------- (11)
SE Gain
= −
(HP)
one-half in SE mode. Control of the
input can
SE/BTL
I
(HP)
be from a logic-level CMOS source, or, more typically,
from a resistor divider network as shown in Figure 59.
If, for example RI (HP) = 10 kΩ and RF (HP) = 10kΩ then
SE Gain (HP) = -1
R
R
F
(LINE)
-------------------- (12)
BTL Gain
= −2
(LINE)
I(LINE)
If, for exampleRI (LINE) = 10kΩ and RF (LINE) = 50kΩ then
BTL Gain (LINE) = -10
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
input low. When a plug is inserted,
SE/BTL
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
input. The benefits of doing this are
SE/BTL
described in the following input MUX operation section.
Mute and Shutdown Mode
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
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.
,
operation section for a description of the
SE/BTL
headphone hack control circuit.
DS5202 Ver 1.6 May. 2005
21
EUTECH [ EUTECH MICROELECTRONICS INC ]
