WM9712CLGEFLSLASHV datasheet(73/78 Pages) WOLFSON

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Production Data

WM9712L

PD, Rev 4.6, November 2011

AC-COUPLED HEADPHONE OUTPUT

The circuit diagram below shows how to connect a stereo headphone to the WM9712L.

C2 220uF

HPOUTL

HPOUTR

HPGND = 0V

C1 220uF

WM9712L

Figure 25 Simple Headphone Output Circuit Diagram

The DC blocking capacitors C1 and C2 together with the load resistance determine the lower cut-off

frequency, fc. Increasing the capacitance lowers fc, improving the bass response. Smaller

capacitance values will diminish the bass response. For example, with a 16

 load and C1 = 220F:

fc = 1 / 2

 RLC1 = 1 / (2 x 16 x 220F) = 45 Hz

DC COUPLED (CAPLESS) HEADPHONE OUTPUT

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

F DC blocking

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

WM9712L

HPOUTL

HPOUTR

OUT3 = AVDD/2

Figure 26 Capless Headphone Output Circuit Diagram (OUT3SRC = 10)

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

HPOUTL/HPOUTR and OUT3, and therefore no DC blocking capacitors are required. However, this

configuration has some drawbacks:



The power consumption of the WM9712L 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 WM9712L, the audio signal will not be transmitted properly.



OUT3 cannot be used for another purpose

WM9712CLGEFL/V Datasheet(PDF) 73 Page - Wolfson Microelectronics plc