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EMC DESIGN GUIDE FOR ST MICROCONTROLLERS

Table 9. Example of HBM/MM ESD test results on ST72F521

Notes:

1. Data based on characterization results, not tested in production.

2.2 ELECTROMAGNETIC INTERFERENCE (EMI)

2.2.1 EMI radiated test

This test correlates with the SAE J1752/3 standard.

This test gives a good evaluation of the contribution of the microcontroller to radiated noise in

an application environment. It takes into account the MCU chip and also the package which

has a major influence on the noise radiated by the device.

Below is the package EMI contribution from the highest to the lowest:

SDIP/DIP

SOP

QFP

TQFP

The test is performed in a Transverse Electromagnetic Mode Cell (TEMCELL) which allows

radiated noise measurement in two directions, rotating the test board by 90°

Test description:

The firmware running is based on a simple application, toggling 2 LEDs through the I/O ports.

The main directives for an SAE PCB are (Figure 8.):

– 100 x 100mm square board

– At least 2-layer board (ideally 4-layer).

– 5mm conductive edges on both sides connected to ground for contact with TEMCELL.

Figure 7. shows a typical example of an MCU EMC test board schematics.

Symbol

Ratings

Conditions

Maximum value

1)

Unit

Electro-static discharge voltage

(Human Body Model)

2000

V

Electro-static discharge voltage

(Machine Model)

200