| 摘要 |
An electrostatic discharge (ESD) protection device (41, 51, 61, 71, 81) coupled across input-output (I/O) (22) and common (23) terminals of a core circuit (24) that it is intended to protect from ESD events, comprises, one or more serially coupled resistor triggered ESD clamp stages (41, 41′, 41″; 71, 71′, 71″), each stage (41, 41′, 41″; 71, 71′, 71″) comprising first (T1, T1′, T1″, etc.) and second transistors (T2, T2′, T2′″ etc.) having a common collector (52, 52′, 52″) and first (26, 26′, 26″) and second (36, 36′, 36″) emitters providing terminals (32, 42; 32′, 42′; 32″, 42″) of each clamp stage (41, 41′, 41″; 71, 71′, 71. A first emitter (25) of the first stage (41, 71) couples to the common terminal (23) and a second emitter (42″) of the last stage (41″, 71′) couples to the I/O terminals (22). Zener diode triggers are not used. Integrated external ESD trigger resistors (29, 29′, 29″; 39, 39′, 39″) (e.g., of poly SC) are coupled between the base (28, 28′, 28″; 38, 38′, 38″) and emitter (26, 26′, 26″; 36, 36′, 36″) of each transistor (T1, T1′, T1″; T2, T2′, T2″). Different resistor values (e.g., ˜0.5 k to 150 k Ohms) give different ESD trigger voltages. Cascading the clamp stages (41, 41′, 41″; 71, 71′) gives even higher trigger voltages. The ESD trigger resistances (29, 29′, 29″; 39, 39′, 39″) are desirably located outside the common collector-isolation wall (741, 742, 743; 741′, 742′, 743″) surrounding the transistors (T1, T1′, T1″; T2, T2′, T2″). |
