WM8973 Wolfson Microelectronics Ltd., WM8973 Datasheet - Page 38

• Manufacturer Part Number: WM8973
• Description: The WM8976 is a low power, high quality stereo codec designed for portable applications such as Digital still camera or Digital Camcorde
• Manufacturer: Wolfson Microelectronics Ltd.

WM8973L
w
THERMAL SHUTDOWN
HEADPHONE OUTPUT
The speaker and headphone outputs can drive very large currents. To protect the WM8973L from
overheating a thermal shutdown circuit is included. If the device temperature reaches approximately
150
amplifiers (outputs OUT1L/R, OUT2L/R and OUT3) will be disabled.
Table 33 Thermal Shutdown
Analogue outputs LOUT1/ROUT1, LOUT2/ROUT2, and OUT3, can drive a 16
load, either through DC blocking capacitors, or DC coupled without any capacitor.
Figure 13 Recommended Headphone Output Configurations
When DC blocking capacitors are used, then their capacitance and the load resistance together
determine the lower cut-off frequency, f
response. Smaller capacitance values will diminish the bass response. Assuming a 16 Ohm load and
C1, C2 = 220 F:
f
In the DC coupled configuration, the headphone “ground” is connected to the OUT3 pin, which must
be enabled by setting OUT3 = 1 and OUT3SW = 00. As the OUT3 pin produces a DC voltage of
AVDD/2 (=VREF), there is no DC offset between LOUT1/ROUT1 and OUT3, and therefore no DC
blocking capacitors are required. This saves space and material cost in portable applications.
It is recommended to connect the DC coupled headphone outputs only to headphones, and not to
the line input of another device. Although the built-in short circuit protection will prevent any damage
to the headphone outputs, such a connection may be noisy, and may not function properly if the
other device is grounded.
SPEAKER OUTPUT
LOUT2 and ROUT2 can differentially drive a mono 8
Figure 14 Speaker Output Connection
The right channel is inverted by setting the ROUT2INV bit, so that the signal across the loudspeaker
is the sum of left and right channels.
c
R23 (17h)
Additional
Control (1)
= 1 / 2 R
REGISTER
0
ADDRESS
C and the thermal shutdown circuit is enabled (TSDEN = 1 ) then the speaker and headphone
Headphone Output using DC blocking
L
C
1
= 1 / (2 x 16
capacitors
8
BIT
TSDEN
LABEL
x 220 F) = 45 Hz
c
. Increasing the capacitance lowers f
0
DEFAULT
speaker as shown below.
Thermal Shutdown Enable
0 : thermal shutdown disabled
1 : thermal shutdown enabled
DC Coupled Headphone Output
(OUT3SW = 00)
PD Rev 4.2 September 2005
DESCRIPTION
c
, improving the bass
or 32
Production Data
headphone
38