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H330S Hardware User Manual
Page 38 of 44
19
AUXI-
I
Audio channel 2 auxiliary MIC input signal -
20
AUXI+
I
Audio channel 2 auxiliary MIC input
21
AGND
GND
Audio GND
22
VSPK
I
Power supply input for audio codec chip’s internal
power amplifier
Recommended to connect to VBAT
5.7.2 Description of Audio Interface Application
Audio input/output signals are differential signals that have good performance in anti-RF-interference.
When connecting to the phone handle, it is not necessary to add audio power amplifier.
As to PCB layout, the wires should have the same length, and should be parallel and as short as possible.
The wires should be wrapped with ground wire. The input and output signals should be separated by
grounding. It would be best to add ESD protection to the audio signal port.
5.7.2.1 Audio Channel 1
Audio channel 1 is a differential audio port for calls through phone handle.
Audio channel 1: level features of MIC input interface
Parameters
Test conditions
Minimum Value
Typical Value Maximum Value Unit
Bias voltage
Without load
2.5
2.6
V
Gain
Programmable,
stepping gain: 2dB
0
16
dB
Designed load
impedance
2.2
Kohm
Audio channel 1: level features of EAR output interface:
Parameters
Test conditions Minimum Value
Typical Value Maximum Value Unit
Output voltage
Without load
1.4
Vpp
Designed load
impedance
32
ohm
DC Bias voltage
1
V
5.7.2.2 Audio Channel 2
Audio channel 2 is a differential audio port for applicable to hands-free calls. .
Note:
Audio channel 2’s downlink can only be used when VSPK power supply is normal. Generally,
