wm9714l Wolfson Microelectronics plc, wm9714l Datasheet - Page 112

• Manufacturer Part Number: wm9714l
• Description: Ac?97 Audio Codec
• Manufacturer: Wolfson Microelectronics plc

WM9714L
DC COUPLED (CAPLESS) HEADPHONE OUTPUT
BTL LOUDSPEAKER OUTPUT
COMBINED HEADSET / BTL EAR SPEAKER
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In the interest of saving board space and cost, it may be desirable to eliminate the 220µF DC
blocking capacitors. This can be achieved by using OUT3 as a headphone pseudo-ground, as shown
below.
Figure 31 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
If the DC coupled output is connected to the line-in of a grounded piece of equipment, then
OUT3 cannot be used for another purpose
SPKL and SPKR can differentially drive a mono 8Ω loudspeaker as shown below.
Figure 32 Speaker Output Connection (INV = 1)
To drive out differentially one of the speaker outputs must be inverted using INV1 or INV2.
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 33 Combined Headset / BTL Ear Speaker
consumed in the OUT3 output buffer.
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.
PP, Rev 3.2, October 2008
Pre-Production
112