wm9711lgefl-v Wolfson Microelectronics plc, wm9711lgefl-v Datasheet - Page 61

• Manufacturer Part Number: wm9711lgefl-v
• Description: Low Power Audio Codec For Portable Applications
• Manufacturer: Wolfson Microelectronics plc

Production Data
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AC-COUPLED HEADPHONE OUTPUT
DC COUPLED (CAPLESS) HEADPHONE OUTPUT
The circuit diagram below shows how to connect a stereo headphone to the WM9711L.
Figure 17 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 16Ω load and C1 = 220µF:
fc = 1 / 2π R
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 18 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:
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WM9711L
WM9711L
The power consumption of the WM9711L 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 WM9711L, the audio signal will not be transmitted properly.
OUT3 cannot be used for another purpose
L
C
1
HPOUTL
HPOUTR
HPGND = 0V
= 1 / (2π x 16Ω x 220µF) = 45 Hz
HPOUTL
HPOUTR
OUT3 = AVDD/2
C1 220uF
C2 220uF
PD Rev 4.3 August 2006
WM9711L
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