WM9714LGEFLSLASHV datasheet(87/94 Pages) WOLFSON

87 / 94 page

Pre-Production

WM9714L

PP Rev 3.0 June 2006

DC COUPLED (CAPLESS) HEADPHONE OUTPUT

In the interest of saving board space and cost, it may be desirable to eliminate the 220

µF DC

blocking capacitors. This can be achieved by using OUT3 as a headphone pseudo-ground, as shown

below.

Figure 29 Capless Headphone Output Circuit Diagram

As the OUT3 pin produces a DC voltage of AVDD/2, there is no DC offset between HPL/HPR and

OUT3, and therefore no DC blocking capacitors are required. However, this configuration has some

drawbacks:

The power consumption of the WM9714L is increased, due to the additional power

consumed in the OUT3 output buffer.

If the DC coupled output is connected to the line-in of a grounded piece of equipment, then

OUT3 becomes short-circuited. Although the built-in short circuit protection will prevent

any damage to the WM9714L, the audio signal will not be transmitted properly.

OUT3 cannot be used for another purpose

BTL LOUDSPEAKER OUTPUT

SPKL and SPKR can differentially drive a mono 8

Ω loudspeaker as shown below.

Figure 30 Speaker Output Connection (INV = 1)

To drive out differentially one of the speaker outputs must be inverted using INV1 or INV2.

COMBINED HEADSET / BTL EAR SPEAKER

In smartphone applications with a loudspeaker and separate ear speaker (receiver), a BTL ear

speaker can be connected at the OUT3 pin, as shown below.

Figure 31 Combined Headset / BTL Ear Speaker

WM9714LGEFL/V Datasheet(PDF) 87 Page - Wolfson Microelectronics plc