wm8961 Wolfson Microelectronics plc, wm8961 Datasheet - Page 56

• Manufacturer Part Number: wm8961
• Description: Ultra-low Power Stereo Codec With 1w Stereo Class D Speaker Drivers And Ground Referenced Headphone Drivers
• Manufacturer: Wolfson Microelectronics plc

CHARGE PUMP
w
WM8961
DC Servo 3
Table 40 DC Servo Filter Bandwidth Control
REGISTER
ADDRESS
R63 (3Fh)
5:4
BIT
Charge Pump
REGISTER
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.
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 1 μ F capacitance or greater at 2V. The VPOS and VNEG supply pins each require a 2 μ F
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
Table 41 Charge Pump Enable
R72 (48h)
DCS_FILT_BW_SERIES[1:0]
1
LABEL
BIT
0
CP_ENA
LABEL
DEFAULT
01
Bandwidth of filter during series
updates. Determines how long a
measurement takes.
00 : 6ms
01 : 275ms
10 : 1.2s
11 : 4.4s
DEFAULT
0
DESCRIPTION
Enable charge-pump
digits
0: disable
1: enable
PP, August 2009, Rev 3.1
DESCRIPTION
Pre-Production
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