Fibocom L610 MiniPCIe Series, Hardware Manual, Page: 44 / 59

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FIBOCOM L610 Series Hardware Guide Page 44 of 59
1 L610 series Support
3.10.2 Analog Audio Interface Define
Table 3-1 Analog audio interface define
Pin Name I/O Pin Comment
MIC_P I 75 MIC input positive
MIC_N I 77 MIC input negative
SPK_P O 73 Speaker output positive
SPK_N O 74 Speaker output negative
MIC_P and MIC_N are used as differential microphone inputs and do not support single-ended input.
ECM are usually used.
SPK_P and SPK_N are used as differential output of the receiver or speaker (external audio amplifier is
required) and do not support single-ended output.
HP_L and HP_R are used as differential output of earphone and do not support single-ended output.
SPK support Class-D and CLASS-AB two output mode, Class-D mode gain level is 0/1.5/3dB, Class-AB
mode gain level is -3/0/1.16dB (3-bit programmable gain).
SPK output power: 800mW@4.2V on 8
Ω
load in Class-D mode, 600mW@4.2V on 8
Ω
load in Class-AB
mode.
The output of internal POW amplifier of that module is in clas-AB mode by default, and can be connected
with external power amplifier, recommend type
：
AW87359FCR (8
Ω2W).
When the power amplifier type needs to be switched, it can send AT instruction to switch and restart to
take effect.
1 AT+GTSET="PAMODESEL",0 A/B
2 AT+GTSET="PAMODESEL",1 D
3.10.3 Preventing TDD and Other Noises
It is recommended to use built-in RF filter dual capacitance (e.g. 10pF and 33pF) when use handheld and
hand free microphone, filter RF interference from the source, greatly improve coupled TDD noise. The
33pF capacitor is used to filter high-frequency interference when the module works at 900MHz and the
10pF capacitor is used to filter high-frequency interference when the module works at 1800MHz. Without
this capacitor, it is possible to hear TDD noise during a call. It should be noted that since the capacitor
syntony depends on the capacitor material and manufacturing process to a large extent, it is necessary to
consult the capacitor supplier to select the most appropriate capacitance value to filter out the high
frequency noise at GSM900/DCS1800.
The severity of High frequency interference in GSM transmission usually depends on the customer
application design. On some cases, The TDD noise of GSM900 is severe, while in other cases, The TDD