WM8753LEBSLASHRV datasheet(48/87 Pages) WOLFSON

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Advanced Information

WM8753L

AI Rev 3.1 June 2004

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

Ω speaker as shown below.

LOUT2

ROUT2

WM8753L

ROUT2INV = 1

SPKR = L-(-R) = L+R

-1

LEFT

MIXER

RIGHT

MIXER

ROUT2VOL

LOUT2VOL

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.

Alternatively it is possible to drive 2 BTL stereo speakers, one between LOUT2 and OUT4, the other

between ROUT2 and OUT3, but only to about 250mW/2 due to the limited drive capability of the

OUT3/OUT4 outputs.

LINE OUTPUT

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

OUT3 and MONO2 can be used as a stereo line-out by setting OUT3SW=11 (reg. 24) and ensuring

the contents of registers 38 and 39 (mono-out mix) are the same as reg. 34 and 35 (left out mix).

Recommended external components are shown below.

AGND

LINE-OUT SOCKET

(LEFT)

1uF

100 Ohm

LOUT1/2

ROUT1/2

WM8753L

100 Ohm

LINE-OUT SOCKET

(RIGHT)

1uF

Figure 13 Recommended Circuit for Line Output

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

Assuming a 10 k

Ω load and C1, C2 = 1µF:

fc = 1 / 2

π (R

L+R1) C1 = 1 / (2

π x 10.1kΩ x 1µF) = 16 Hz

Increasing the capacitance lowers fc, improving the bass response. Smaller values of C1 and C2 will

diminish the bass response. The function of R1 and R2 is to protect the line outputs from damage

when used improperly.

INTERRUPT CONTROLLER

The WM8753L can generate an interrupt based on seven separate level-sensitive sources. Each

source has programmable polarity and can be individually enabled. On detecting an enabled request

with the correct polarity, a status latch for that source is set. If any of the status latches are set, the

interrupt controller generates an internal INT signal that can be routed to one of the general purpose

pins. The value of the status latches can be obtained over the control interface using the read/write

mode. Each latch is cleared by disabling the source in question. Once cleared, the source can be re-

enabled if desired. Figure 14 illustrates the operation of the interrupt controller circuit.

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