st3237eb STMicroelectronics, st3237eb Datasheet - Page 10

• Manufacturer Part Number: st3237eb
• Description: ? 15 Kv Esd Protected, 1 ?a, 3 To 5.5 V, 250 Kbps Rs-232 Transceiver With Stand-by
• Manufacturer: STMicroelectronics

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Application note
This application note describes the procedure for determining the susceptibility and the test
method to verify ST ESD advanced protection on RS-232 or RS485 I/O device.
Static electricity is defined as an electrical charge caused by an imbalance of electrons on
the surface of a material. This imbalance of electrons produces an electric field that can be
measured and that can influence other objects at a distance. Electrostatic discharge is
defined as the transfer of charge between bodies at different electrical potentials.
Electrostatic discharge (ESD) can change the electrical characteristics of a semiconductor
device, degrading or destroying it. Any input or output port (I/O) allows access
communication with other pieces of equipment by external connectors. These connectors
are directly linked by the I/O pins of RS-232 or RS485 interface. ST provides the E-series by
advanced high ESD protection structure. The protection functionality is tested in two
different conditions:
The first model is used to simulate the HUMAN BODY MODEL (HBM) event. A similar
discharge can occur from a charged conductive object, such as a metallic tool or fixture. The
model used to characterize this event is known as the machine model. A human body model
circuit and waveform is presented in figures below.
Human body model circuit
Human body model current waveform