WM8903LGEFK/RV Wolfson Microelectronics, WM8903LGEFK/RV Datasheet - Page 37

• Manufacturer Part Number: WM8903LGEFK/RV
• Description: Audio CODECs ULTRA LOW PWR HI FI CODEC
• Manufacturer: Wolfson Microelectronics

Specifications of WM8903LGEFK/RV

• Audio Codec Type: Stereo Codec
• No. Of Adcs: 2
• No. Of Dacs: 2
• No. Of Input Channels: 6
• No. Of Output Channels: 8
• Adc / Dac Resolution: 24bit
• Sampling Rate: 96kHz
• Operating Temperature Range: -40°C To +85°C
• Rohs Compliant: Yes
• Adcs / Dacs Signal To Noise Ratio: 96dB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Production Data
ELECTRET CONDENSER MICROPHONE INTERFACE
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Electret Condenser microphones may be connected as single-ended or differential inputs to the Input
PGAs described in the “Analogue Input Signal Path” section. The WM8903 provides a low-noise
reference voltage suitable for biasing electret condenser microphones.
The MICBIAS reference is provided on the MICBIAS pin. This reference voltage is enabled by setting
the MICBIAS_ENA register bit, as defined in Table 6.
Table 6 MICBIAS Control
MICBIAS CURRENT DETECT
A MICBIAS Current Detect function is provided for external accessory detection. This is provided in
order to detect the insertion/removal of a microphone or the pressing/releasing of the microphone
‘hook’ switch; these events will cause a significant change in MICBIAS current flow, which can be
detected and used to generate a signal to the host processor.
The MICBIAS current detect function is enabled by setting the MICDET_ENA register bit. When this
function is enabled, two current thresholds can be defined, using the MICDET_THR and
MICSHORT_THR registers. When a change in MICBIAS current which crosses either threshold is
detected, then an interrupt event can be generated. In a typical application, accessory insertion
would be detected when the MICBIAS current exceeds MICDET_THR, and microphone hookswitch
operation would be detected when the MICBIAS current exceeds MICSHORT_THR.
The current detect threshold functions are both inputs to the Interrupt control circuit and can be used
to trigger an Interrupt event when either threshold is crossed. Both events can also be indicated as
an output on a GPIO pin - see “General Purpose Input/Output (GPIO)”.
The current detect thresholds are enabled and controlled using the registers described in Table 7.
Performance parameters for this circuit block can be found in the “Electrical Characteristics” section.
Hysteresis and filtering is also provided in the both current detect circuits to improve reliability in
conditions where AC current spikes are present due to ambient noise conditions. These features are
described in the following section. Further guidance on the usage of the MICBIAS current monitoring
features is also described in the following pages.
R6 (06h)
Mic Bias
Control 0
R6 (06h)
Mic Bias
Control 0
REGISTER
REGISTER
ADDRESS
ADDRESS
BIT
BIT
5:4
3:2
0
MICBIAS_ENA
MICDET_THR
[1:0]
MICSHORT_TH
R [1:0]
LABEL
LABEL
DEFAULT
DEFAULT
00
00
0
MICBIAS Enable
0 = disabled
1 = enabled
MICBIAS Current Detect Insertion
Threshold
00 = 0.063mA
01 = 0.26mA
10 = 0.45mA
11 = 0.635mA
Values are scaled with AVDD.
Figures shown are based on
AVDD=1.8V.
MICBIAS Short Circuit Button Push
Threshold
00 = 0.52mA
01 = 0.77mA
10 = 1.2mA
11 = 1.43mA
Values are scaled with AVDD.
Figures shown are based on
AVDD=1.8V.
PD, Rev 4.0, September 2010
DESCRIPTION
DESCRIPTION
WM8903
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