WM8971LEFLSLASHR datasheet(35/56 Pages) WOLFSON

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Advanced Information

WM8971L

AI Rev 3.0 March 2004

THERMAL SHUTDOWN

The speaker and headphone outputs can drive very large currents. To protect the WM8971L from

overheating a thermal shutdown circuit is included. If the device temperature reaches approximately

150

0C and the thermal shutdown circuit is enabled (TSDEN = 1) then the analogue outputs

(OUT1L/R, OUT2L/R) will be disabled.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R23 (17h)

Additional

Control (1)

TSDEN

Thermal Shutdown Enable

0 : thermal shutdown disabled

1 : thermal shutdown enabled

Table 27 Thermal Shutdown

HEADPHONE OUTPUT

Analogue outputs LOUT1/ROUT1 and LOUT2/ROUT2, can drive a 16

Ω or 32Ω headphone load,

through DC blocking capacitors.

Figure 11 Recommended Headphone Output Configuration

The DC blocking capacitors and the load resistance together determine the lower cut-off frequency,

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

will diminish the bass response. Assuming a 16 Ohm load and C1, C2 = 220

µF:

fc = 1 / 2

π RLC1 = 1 / (2π x 16Ω x 220µF) = 45 Hz

SPEAKER OUTPUT

LOUT2 and ROUT2 can differentially drive a mono 8

Ω speaker as shown below.

Figure 12 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.

LINE OUTPUT

The analogue outputs, LOUT1/ROUT1 and LOUT2/ROUT2, can be used as line outputs.

Recommended external components are shown below.

Figure 13 Recommended Circuit for Line Output

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