CSR8615A04-IQQF-R View Datasheet(PDF) - Unspecified
Part Name
Description
MFG CO.
'CSR8615A04-IQQF-R' PDF : 114 Pages View PDF
9.2.13 Microphone Input
CSR8615 QFN contains an independent low-noise microphone bias generator. The microphone bias generator is
recommended for biasing electret condensor microphones. Figure 9.4 shows a biasing circuit for microphones with
a sensitivity between about ‑40 to ‑60dB (0dB = 1V/Pa).
Where:
â– The microphone bias generator derives its power from VBAT or 3V3_USB and requires no capacitor on its
output.
■The microphone bias generator maintains regulation within the limits 70μA to 2.8mA, supporting a 2mA
3 source typically required by 2 electret condensor microphones. If the microphone sits below these limits,
01 then the microphone output must be pre-loaded with a large value resistor to ground.
, 2 ■Biasing resistors R1 is 2.2kΩ.
16 ■The input impedance at LINE/MIC_AN and LINE/MIC_AP is typically 6kΩ.
er â– C1 and C2 are 100/150nF if bass roll-off is required to limit wind noise on the microphone.
mb ■R1 sets the microphone load impedance and are normally around 2.2kΩ.
epte Microphone Bias
S (MIC_BIAS)
onday, C1 LINE/MIC_AP
- M R1
n C2 LINE/MIC_AN
om.c + MIC1
Input
Amplifier
checomm.c Figure 9.4: Microphone Biasing
apa The microphone bias characteristics include:
o - â– Power supply:
sa â– CSR8615 QFN microphone supply is VBAT or 3V3_USB
s T â– Minimum input voltage = Output voltage + drop-out voltage
e â– Maximum input voltage is 4.3V
jam â– Drop-out voltage:
for â– 300mV maximum
d â– Output voltage:
are â– 1.8V or 2.6V
rep â– Tolerance 90% to 110%
P â– Output current:
■70μA to 2.8mA
â– No load capacitor required
9.2.14 Line Input
Figure 9.5 and Figure 9.6 show 2 circuits for line input operation and show connections for either differential or single-
ended inputs.
In line input mode, the input impedance of the pins to ground varies from 6kΩ to 34kΩ depending on input gain
setting.
Pre-production Information
© Cambridge Silicon Radio Limited 2013
Confidential Information - This Material is Subject to CSR's Non-disclosure Agreement
Page 43 of 114
CS-303726-DSP3
www.csr.com
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