Selecting an ESD Suppressor

Littelfuse offers three device technologies for the suppression of ESD events and other EMC-related transients. These are the MultiLayer Metal Oxide Varistor, Silicon (SCR/Diode Array and TVS Avalanche Diode Arrays) and Polymeric Voltage Variable Material technologies. Though these products have different characteristics, they have the common goal of protecting sensitive components from transients that threaten their survivability and functionality. Additionally, EMC legislation, or other immunity requirements, may mean that existing products require suppression devices in order to be compliant with the applicable immunity test. As with all decision-making processes, information is the key when considering the use of ESD suppressors. It is critical that the circuit characteristics are defined. For example, the capacitance value of the ESD suppressor will limit its usage on communication lines. As the speed of the data increases, the capacitance (if it is too large) can distort or attenuate the data. Ideally, the Design Engineer will gather basic circuit information such as data rate, allowable leakage current, line voltage, size constraints, and number of lines that require protection. This information can then be used to compare the circuit conditions to the ESD suppressor characteristics to find the best "match". To help with the "matching" process, a suppressor characteristic table is included below, and a selection flowchart can be found on the next page.