WM8900LGEFK/RV Wolfson Microelectronics, WM8900LGEFK/RV Datasheet - Page 57

• Manufacturer Part Number: WM8900LGEFK/RV
• Description: Audio CODECs Ultra Low Power Hi-Fi CODEC
• Manufacturer: Wolfson Microelectronics

Specifications of WM8900LGEFK/RV

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Production Data
MASTER BIAS
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Table 40 Charge Pump Control
HEADPHONE AMPLIFIER
The Headphone amplifier input (HP_INL / HP_INR) must be coupled to the LINEOUT_2L /
LINEOUT_2R via a small DC blocking capacitor as illustrated in Figure 20. A high pass filter is
formed between this capacitor and the impedance of the headphone amplifier, which is
approximately 20kΩ. The choice of capacitor determines the high pass filter cut-off frequency as
detailed in Table 41, and can be chosen to fit the desired bass response requirements.
Table 41 Headphone AC Coupling Capacitor
(±5%) resistor and a 20nF (±20%) capacitor, as illustrated in the recommended external
components diagram..
The Headphone amplifier can be controlled via the register settings described in Table 42. See
also Table 9 for additional control fields that may be used to minimise pops and clicks under
certain mode changes.
Table 42 Headphone Amplifier Control
If the headphone output is being used in a mono configuration, it is a requirement that the un-used
OUT2 volume PGA ( R53 (0x35) or R54 (0x36)) should be set up with minimum volume setting and
not muted, i.e. must clear bits 6:0. This ensures that the Class G power saving features of
WM8900 will function correctly for the mono output channel.
The overall analogue master bias current can be optimised by the MASTER_BIAS register bits.
Note that the optimum setting for minimum power consumption is not the power-on default value.
The various power saving options are discussed in Table 45.
Table 43 Master Bias Control
A zobel network is required to stabilise the amplifier. The zobel network should comprise a 50 ohm
R3 (03h)
Power
Management 3
R58 (3Ah)
Headphone
Control 1
R116 (74h)
Master Bias
Control
Master Bias
Control
REGISTER
ADDRESS
REGISTER
CAPACITOR VALUE
REGISTER
ADDRESS
ADDRESS
0.47 uF
1 uF
7
BIT
8:7
BIT
BIT
7
6
MASTER_BIAS
CP_ENA
HP_IPSTAGE_ENA
HP_OPSTAGE_ENA
-3DB CUT-OFF FREQUENCY
LABEL
LABEL
LABEL
17 Hz
8 Hz
DEFAULT
DEFAULT
DEFAULT
10
0
0
0
Adjusts master bias
00 = Reserved
01 = 0.75 bias
10 = full bias - default
11 = Reserved
Headphone input stage Enable
0 = Headphone input stage
disabled
1 = Headphone input stage
enabled
Headphone output stage Enable
0 = Headphone output stage
disabled
1 = Headphone output stage
enabled
Charge Pump Enable
0 = Disable charge pump
1 = Enable charge pump
Must be enabled when the
headphone output is used.
PD, August 2008, Rev 4.0
DESCRIPTION
DESCRIPTION
DESCRIPTION
WM8900
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