SIM800L datasheet(37/73 Pages) SIMCOM

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Figure 32: Speaker with amplifier reference circuit

4.7.3.

Audio Electronic Characteristic

Table 15: Microphone input characteristics

Parameter

Min

Typ

Max

Unit

Microphone biasing voltage

1.9

2.2

Working current

2.0

Input impedance(differential)

KΩ

Idle channel noise

-67

dBm0

Input level:-40dBm0

SINAD

Input level:0dBm0

Table 16: Audio output characteristics

Parameter

Conditions

Min

Typ

Max

Unit

RL=32 Ω receiver

Normal output

RL=8 Ω speaker

1080

4.7.4.

TDD

Audio signal could be interferenced by RF signal. Coupling noise could be filtered by adding 33pF and 10pF

capacitor to audio lines. 33pF capacitor could eliminate noise from GSM850/EGSM900MHz, while 10pF

capacitor could eliminate noise from DCS1800/PCS1900Mhz frequency. Customer should develop this filter

solution according to field test result.

GSM antenna is the key coupling interfering source of TDD noise. Thereat, pay attention to the layout of audio

lines which should be far away from RF cable, antenna and VBAT pin. The bypass capacitor for filtering should

be placed near module and another group needs to be placed near to connector.

Conducting noise is mainly caused by the VBAT drop. If audio PA was powered by VBAT directly, then there

SIM800H&SIM800L_Hardware Design_V2.02

2015-07-27

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