WM8961 datasheet(56/116 Pages) WOLFSON

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WM8961

Pre-Production

PP, August 2009, Rev 3.1

DC SERVO FILTER BANDWIDTH

The DC Servo filter bandwidth can be modified to change the time taken to measure and correct the

DC offset. The longer the time taken to measure the offset, then the more accurate the correction will

be.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R63 (3Fh)

DC Servo 3

5:4

DCS_FILT_BW_SERIES[1:0]

Bandwidth of filter during series

updates. Determines how long a

measurement takes.

00 : 6ms

01 : 275ms

10 : 1.2s

11 : 4.4s

Table 40 DC Servo Filter Bandwidth Control

CHARGE PUMP

The WM8961 incorporates a dual-mode Charge Pump which generates the +ve (VPOS) and –ve

(VNEG) supply rails for the headphone output driver. The Charge Pump has a single supply input,

CPVDD, and generates split rails VPOS and VNEG according to the selected mode of operation,

which means that the headphone driver is capable of driving headphones without the need for large

AC coupling capacitors. The Charge Pump connections are illustrated in Figure 28 (see ‘applications

information’ for external component values). An input decoupling capacitor may also be required at

CPVDD, depending upon the system configuration.

Figure 28 Charge Pump External Connections

Three external capacitors are needed for the charge pump. The fly-back pins (CFB1 and CFB2)

require a 1μF capacitance or greater at 2V. The VPOS and VNEG supply pins each require a 2μF

capacitance decoupling capacitor at 2V.

ENABLING THE CHARGE PUMP

An external clock (MCLK) input is required for the charge pump operation. The minimum MCLK

frequency for the specified charge pump performance is 2.8224MHz.

The charge pump is enabled by setting the CP_ENA bit. DVDD and CPVDD must be active before the

charge pump is enabled. The charge pump initialisation time is specified in the Electrical

Characteristics. DVDD and CPVDD must be active before the charge pump is enabled.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R72 (48h)

Charge Pump

CP_ENA

Enable charge-pump

digits

0: disable

1: enable

Table 41 Charge Pump Enable

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