WM8351 datasheet(87/330 Pages) WOLFSON

87 / 330 page

Production Data

WM8351

PD, April 2012, Rev 4.5

Notes:

The above figures illustrate the headphone connections to outputs OUT1L and OUT1R. The

equivalent configurations apply equally to OUT2L and OUT2R.

The DC-coupled configuration illustrated in Figure 47 shows OUT4 (muted) being used as the

Ground Return connection. The same capability may alternatively be provided using OUT3.

Twin headphone output (OUT1L, OUT1R, OUT2L and OUT2R) is possible, using a shared

Ground Return connection via any of OUT3, OUT4, HPCOM or AGND.

Capless operation is not possible when using the HPCOM feature.

When DC blocking capacitors are used their capacitance 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. For a 16

 load and a capacitance of

220

F, the following derivation of cut-off frequency applies:

fc = 1 / 2 RLC1 = 1 / (2 x 16 x 220F) = 45 Hz

In the DC coupled configuration, the headphone “ground” is connected to VMID. The OUT3 or OUT4

pins can be configured as DC output drivers by de-selecting all inputs to the OUT3 or OUT4 mixers.

The DC voltage on VMID in this configuration is equal to the DC offset on the OUT1L and OUT2L

pins therefore no DC blocking capacitors are required. This saves space and material cost in portable

applications.

It is recommended to only use the DC coupled configuration to drive headphones, and not to use this

configuration to drive the line input of another device.

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