AN1709 datasheet(12/38 Pages) STMICROELECTRONICS

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EMC DESIGN GUIDE FOR ST MICROCONTROLLERS

Figure 6. Absolute Electrical Sensitivity test models

2.1.3.1 Human Body Model Test Sequence

The HBM ESD pulse simulates the direct transfer of electrostatic charge, from the Human

Body, to a test device. A 100pF capacitor is discharged through a switching component and a

1.5 Kohm series resistor. This is currently the most requested industry model, for classifying

device sensitivity to ESD.

– CL is loaded through S1 by the HV pulse generator.

– S1 switches position from generator to R.

– A discharge from CL through R (body resistance) to the µC occurs.

– S2 must be closed 10 to 100ms after the pulse delivery period to ensure the µC is not left in

charge state. S2 must be opened at least 10ms prior to the delivery of the next pulse.

2.1.3.2 Machine Model Test Sequence

The MM ESD pulse emulates the rapid direct transfer of electrostatic charge, from a charged

conductive object, such as a metallic tool or fixture, to a test device. This model consists of a

discharged 200pF capacitor, with no series resistor. The demand for MM ESD testing has in-

creased, with the replacement of individual packaging by automated systems.

– CL is loaded through S1 by the HV pulse generator.

– S1 switches position from generator to the µC.

– A discharge from CL to the µC occurs.

– S2 must be closed 10 to 100ms after the pulse delivery period to ensure the µC is not left in

charge state. S2 must be opened at least 10ms prior to the delivery of the next pulse.

R (machine resistance), in series with S2, ensures a slow discharge of the µC.

Table 9 shows how HBM/MM ESD test results are presented in ST datasheets.

µC

R=1500W

HIGH VOLTAGE

CL=100pF

PULSE

GENERATOR

µC

HIGH VOLTAGE

CL=200pF

PULSE

GENERATOR

HUMAN BODY MODEL

MACHINE MODEL

AN1709 Datasheet(PDF) 12 Page - STMicroelectronics