Huawei MC509 CDMA LGA Audio Interface, ESD Protection for the UIM Card Interface, Analogue Audio

To meet the requirements of ETSI TS 102 230protocols and electromagnetic compatibility (EMC) authentication, the UIM card socket should be placed near the LGA interface (it is recommended that the PCB circuit connecting the LGA interface and the UIM card socket not exceed 100mm), because a long circuit may lead to wave distortion, thus affecting signal quality.

It is recommended that the user should wrap the area adjacent to the UIM_CLK and UIM_DATA signal wires with a ground wire. The GND pin of the UIM card socket and the GND pin of the UIM card must be well connected to the power GND pin supplying power to the MC509 module.

A 0.1μF capacitor is placed between the UIM_VCC and GND pins in a parallel manner. Three 10pF or 33pF capacitors are placed between the UIM_DATA and GND pins, the UIM_RST and GND pins, and the UIM_CLK and GND pins in parallel to filter interference from RF signals.

It is not recommended that pull the UIM_DATA pin up during design as a 15000- ohm resistor is used to connect the UIM_DATA pin to the UIM_VCC.

3.7.3ESD Protection for the UIM Card Interface

It is recommended to take electrostatic discharge (ESD) protection measures near the UIM card socket. Figure 3-11shows ESD protection circuit of the UIM card, in which the transient voltage suppressor (TVS) diode is placed as close as possible to the UIM card socket, and the GND pin of the ESD protection component is well connected to the power GND pin that supplies power to the MC509 module.

Figure 3-11ESD protection circuit on the UIM card

3.8 Audio Interface

3.8.1 Analogue Audio

The MC509 provides two audio I/O channels (Data only doesn’t support the voice function).