WM8731LSEFL/R Wolfson Microelectronics, WM8731LSEFL/R Datasheet - Page 24

• Manufacturer Part Number: WM8731LSEFL/R
• Description: Audio CODECs STEREO CODEC w/ HP 28-pin
• Manufacturer: Wolfson Microelectronics

Specifications of WM8731LSEFL/R

• Number Of Adc Inputs: 1
• Number Of Dac Outputs: 1
• Conversion Rate: 96 KSPS
• Interface Type: Serial (2-Wire, 3-Wire, I2S)
• Resolution: 18 bit, 20 bit
• Operating Supply Voltage: - 0.3 V to + 3.63 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: QFN EP
• Minimum Operating Temperature: - 40 C
• Number Of Channels: 2 ADC/2 DAC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

WM8731 / WM8731L
w
Or alternatively to calculate the value of Rmic to achieve a given gain, G1.
The internal 50k and 10k resistors have a tolerance of 15%. For Rmicext = 90k G = 0.5 (-6dB) and
for Rmicext = 0 G = x10 (14dB).
The 2
gain for low sensitivity microphones.
The microphone input can therefore be configured with a variable gain of between -6dB and 14dB on
the 1
input signal in the range –6dB to 34dB to be catered for.
The ADC Full Scale input is 1.0V rms at AVDD = 3.3 volts. Any voltage greater than full scale will
possibly overload the ADC and cause distortion. Note that the full scale input tracks directly with
AVDD. Stage 1 and Stage 2 gains should be configured so that the ADC receives a maximum signal
equal to its full scale for maximising the signal to noise.
The software control for the MICIN is shown in Table 4. Note that the Microphone Mute only mutes
the input to the ADC, this will still allow the Microphone Input signal to pass to the line output in
Sidetone Mode.
Table 4 Microphone Input Software Control
The microphone input is biased internally through the operational amplifier to VMID. Whenever the
line inputs are muted the MICIN input is kept biased to VMID using special anti-thump circuitry. This
reduces any audible clicks that may otherwise be heard when re-activating the input.
The application drawing for the microphone is shown in Figure 13.
Figure 13 Microphone Input and Bias Application Drawing
Recommended component values are C1 = 220pF (npo ceramic), C2 = 1μF, R1 = 680 Ω, R2 = 47k.
Rmic values depends on gain setting (see above).
0000100
Analogue Audio
Path Control
REGISTER
ADDRESS
st
MICROPHONE
nd
stage, and an additional fixed 0dB or 20dB on the 2
stage comprises a 0dB gain stage that can be software configured to provide a fixed 20dB of
FROM
Rmic = (50k/G1) – 10k
0
1
BIT
AGND
MICBOOST
MUTEMIC
LABEL
R1
R2
AGND
0
1
DEFAULT
AGND
C1
nd
C2
1 = Enable Boost
0 = Disable Boost
Line Input Mute to ADC
1 = Enable Mute
0 = Disable Mute
Microphone Input Level Boost
stage. This allows for all gains to the
MICBIAS
DESCRIPTION
Rmic
PD, Rev 4.8, April 2009
Production Data
MICIN
24