Texas Instruments PCM182 EVM Series, Руководство пользователя, Страница: 6 / 21

4 PCM182xEVM /PCM182xQ1EVM Inputs
The PCM1820/PCM1820-Q1 device is intended to be driven with differential line or microphone inputs. Each
of the inputs has a 1-µF AC coupling film capacitor. Coupled with the 2.5-kΩ input impedance of PCM1820/
PCM1820-Q1 , this sets the high pass filter cutoff frequency at approximately 63-Hz. PCM1821/PCM1821-Q1
has an input impedance of 10-kΩ, setting the cutoff frequency at 16-Hz. This can be adjusted by replacing the
input AC coupling capacitors on the EVM if necessary.
Figure 4-1 shows the architecture of the inputs to the
evaluation module. The EVM supports a differential full scale input range of 2 VRMS with an AVDD of 3.3 V.
Please Note: PCM1822EVM/PCM1822Q1EVM is set up to support single ended inputs.
PCM182x
MIC2
IN2M
IN2P
IN2M IN2P
J21
J12
MICBIAS
J11
MIC1
IN1P
IN1M
IN1P IN1M
J16
J15
MICBIAS
J14
J23 J25 J24
J22
Figure 4-1. PCM182x /PCM182x-Q1 Input Architecture
4.1 Onboard Microphone Inputs
PCM182x EVM/PCM182xQ1 EVM has two onboard differential microphones that can be routed to the inputs
with jumpers. The microphones require a bias be applied to MPWR. MPWR can be tied to AVDD on J4, or
to MICBIAS if using a device that supports this feature. Note that the PCM182x/PCM182x-Q1 do not have
an integrated MICBIAS and this option is provided for future devices that might incorporate this feature. The
following jumpers need to be installed to use the onboard mics: J4, J11,J12, J14, J15, J16, and J21.
If the onboard mics are used, leave the J1 and J2 headers unconnected to preserve the microphone
performance.
PCM182xEVM /PCM182xQ1EVM Inputs www.ti.com
6 PCM182xEVM/PCM182xQ1EVM EVM User's Guide SBAU363A – FEBRUARY 2021 – REVISED MARCH 2022
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