SIM800C datasheet(31/52 Pages) SIMCOM

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SIM800C_Hardware_Design_V1.02

2015-4-27

Input level:0dBm0

Table 14: Audio output characteristics

Parameter

Conditions

Min

Typ

Max

Unit

Normal output

RL=32 Ω receiver

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

will be some cheep noise from speaker output easily. So it is better to put big capacitors and ferrite beads near

audio PA input.

TDD noise has something to do with GND signal. If GND plane is not good, lots of high-frequency noises will

interference microphone and speaker over bypass capacitor. So a good GND during PCB layout could avoid

TDD noise.

4.8. SIM Card Interface

The SIM interface complies with the GSM Phase 1 specification and the new GSM Phase 2+ specification for

FAST 64kbps SIM card. Both 1.8V and 3.0V SIM card are supported. The SIM interface is powered from an

internal regulator in the module.

4.8.1.

SIM Card Application

Table 15: SIM pin definition

Pin name

Pin number

Function

SIM_VDD

Voltage supply for SIM card. Support 1.8V or 3V SIM card

SIM_DATA

SIM data input/output

SIM_CLK

SIM clock

SIM_RST

SIM reset

SIM_DET

SIM card detection

It is recommended to use an ESD protection component such as ST (www.st.com ) ESDA6V1-5W6 or ON

SEMI (www.onsemi.com ) SMF05C. The SIM card peripheral components should be placed close to the SIM

card holder. The reference circuit of the 8-pin SIM card holder is illustrated in the following figure.

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