wm8903 Wolfson Microelectronics plc, wm8903 Datasheet - Page 154

• Manufacturer Part Number: wm8903
• Description: Ultra Low Power Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8903
Table 77 Capacitor Examples
MIC DETECTION SEQUENCE USING MICBIAS CURRENT
w
VPOS, VNEG
CAPACITOR
CFB1-CFB2
CPVDD
CAPACITANCE
1μF at 2vDC
2μF at 2vDC
REQUIRED
The zobel network (C19,20,21,22, R9,10,11,12 in Figure 64) is required on HPOUTL/R and
LINEOUTL/R if the output is being used. Stability of either set of outputs across all process corners
cannot be guaranteed without the zobel network. If any Ground-referenced output pin is not required,
the zobel network components can be omitted from that output pin, and the pin can be left floating.
The zobel network requirement is detailed further in the applications note WAN_0212 “Class W
Headphone Impedance Compensation”.
This section details an example sequence which summarises how the host processor can configure
and detect the events supported by the MICBIAS current detect function (see “Electret Condenser
Microphone Interface”):
Figure 65 shows an example of how the MICBIAS current flow varies versus time, during mic
insertion and hook switch events. The Y axis is annotated with the Mic detection thresholds, and the
X axis is annotated with the stages of an example sequence as detailed in Table 78, to illustrate how
the host processor can implement mic insertion and hook switch detection.
The sequence assumes that the polling of the control interface, by checking the interrupt flags, has
been used to monitor changes in the microphone insertion or hook switch detection functions, rather
than connection of a WM8903 GPIO. This means that the maximum possible mechanical bounce
times for mic insertion and removal must be understood by the software programmer.
At every step in the following process, the host processor should poll the interrupt status register.
•
•
(1) 2.2μF
(2) 4.7μF
VALUE
2.2μF
Mic insertion/removal
Hook switch press/release
VOLTAGE
RATED
6.3v
6.3v
10v
EXAMPLE OF CURRENT CAPACITOR TECHNOLOGY
DIELECTRIC
X5R
X5R
X5R
CASE
0402
0603
0402
SIZE
(EIA)
FACTURER
MuRata
MuRata
MuRata
MANU-
Kemet
GRM155R60J225ME15_EIA
PP, Rev 3.1, August 2009
GRM155R60J475M_EIA
GRM188R61A225KE34D
C0402C225M9PAC
P/N
Pre-Production
154