WM8753 Wolfson Microelectronics plc, WM8753 Datasheet - Page 47

• Manufacturer Part Number: WM8753
• Description: HI FI AND TELEPHONY DUAL CODEC
• Manufacturer: Wolfson Microelectronics plc

WM8753L
HEADPHONE OUTPUT
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Table 47 Thermal Shutdown
Figure 11 Recommended Headphone Output Configurations
Table 46 GPIO4 Control
THERMAL SHUTDOWN
The speaker and headphone outputs can drive very large currents. To protect the WM8753L from
overheating a thermal shutdown circuit is included. If the device temperature reaches approximately
150
amplifiers (outputs OUT1L/R, OUT2L/R, OUT3 and OUT4) will be disabled if TSDADEN is set. The
thermal shutdown may also be configured to generate an interrupt. See the GPIO and Interrupt
Controller section for details.
Analogue outputs LOUT1/ROUT1, LOUT2/ROUT2, and OUT3/OUT4, can drive a 16
headphone load, either through DC blocking capacitors, or DC coupled without any capacitor.
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 load and C1,
C2 = 220 F:
f
In the DC coupled configuration, the headphone “ground” is connected to the OUT3 or OUT4 pin.
OUT3 is enabled by setting OUT3 = 1 and OUT3SW = 00, while OUT4 is enabled by setting OUT4=1
and OUT4SW=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.
c
Headphone Output using DC blocking capacitors
R27 (1Bh)
GPIO Control
(1)
R45 (2Dh)
Output
Control
R63 (3Fh)
Additional
Control
= 1 / 2 R
0
WM8753L
REGISTER
REGISTER
ADDRESS
ADDRESS
C and the thermal shutdown circuit is enabled (TSDEN = 1 ) then the speaker and headphone
L
C
LOUT1/2
ROUT1/2
HPGND = 0V
1
= 1 / (2 x 16 x 220 F) = 45 Hz
4:3
4
6
C1 220uF
C2 220uF
BIT
BIT
GPIO4M[2:0]
TSDEN
TSDADEN
LABEL
LABEL
c
. Increasing the capacitance lowers f
0
0
00
DEFAULT
DEFAULT
WM8753L
Configures GPIO4 pin:
000 = Input only.
001 = unused.
010 = input only with pull-down.
011 = Input only with pull-up.
100 = Drive low.
101 = Drive high.
110 = SDOUT from control interface
111 = INT from interrupt controller
Thermal Shutdown Enable
1 : thermal shutdown disabled
0 : thermal shutdown enabled
Thermal Shutdown Control
0 : Thermal shutdown will not disable
speaker and headphone outputs
1 : Thermal shutdown will automatically
disable speaker and headphone outputs
(OUT3SW = 00 or OUT4SW=00)
DC Coupled Headphone Output
LOUT1/2
ROUT1/2
OUT3/OUT4 = VREF
DESCRIPTION
DESCRIPTION
c
AI Rev 3.1 June 2004
Advanced Information
, improving the bass
or 32
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