DocID026513 Rev 1

3/21

AN4541

Market environment

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1

Market environment

All sensitive electronic equipment such as mobile phones, computers and peripherals

require protection against electrostatic discharge using components able to clamp high

voltages, as defined by each standard level, including IEC61000-4-2. Introducing a

clamping device between all the parts directly in contact with external environment is a key

factor in obtaining reliable and robust equipment, and these devices have to be as

transparent as possible in normal working mode in order to maintain signal integrity.

Filtering unwanted frequencies is another interesting feature which, combined with the

above mentioned clamping technology, can save PCB area and cost.

1.1

STMicroelectronics solutions

STMicroelectronics produces three different devices suitable for this application and

compliant with the standard, which integrate two kinds of pull-up resistor values and the

possibility of implementing electrical card detection:

•

EMIF06-MSD04F3

•

EMIF06-USD04F3

•

EMIF06-MSD03F3

The schematics of these devices are shown below.

Figure 1. STMicroelectronics EMI filter for SD card offer

The basic characteristics of these three filters are the same, especially with respect to the

key line capacitance feature. Therefore, all discussion is based on the EMIF06-MSD04F3.

This application note describes the following topics:

1.

Filter structure

2.

Clamping characteristics

3.

SD3.0 timing constraints and PCB layout recommendations

4.

Rejection capabilities

5.

Electrical card detection capability