How to read datasheets
A datasheet states "ESD rating: HBM ±2 kV, CDM ±500 V." Which is the correct interpretation of these values?
- AThey are component-level ratings assuming handling of the part, not ratings for ESD applied to external terminals of the finished equipment
- BThe part withstands ESD up to ±2 kV, so no added protection components are needed even if it is connected directly to the equipment's external connector
- CHBM and CDM are different names for the same test, and CDM, with the smaller value, correctly represents the part's actual robustness
Show answer and explanation
Answer: A. They are component-level ratings assuming handling of the part, not ratings for ESD applied to external terminals of the finished equipment
HBM (human body model) simulates a discharge when a charged person touches a pin, and CDM (charged device model) simulates a discharge when a pin of a charged part touches metal; both are component-level ratings assuming handling in an ESD-controlled factory. Connectors and other parts of finished equipment are subject to far greater energy, such as ±8 kV contact discharge in system-level tests like IEC 61000-4-2. Pins brought out to the outside should, as a rule, be given separate protection components such as TVS diodes.