Early trigger of ESD protection device by an oscillation circuit
AssigneeWinbond Electronics Corp.
InventorsShi-Tron Lin, Hao-Luen Tien, Shyh-Chyi Wong
Life of this patent
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Abstract
A transient oscillating circuit is provided to generate a series of current pulses for triggering turn-on of an ESD protection device. As VDD-to-VSS voltage increases rapidly in the initial ESD event, the series of current pulses injects minority carriers into the pwell of an NMOS transistor via an adjacent n+/pwell diode. These minority carriers flow toward the drain-substrate junction of the NMOS transistor such that the NMOS transistor is triggered at a trigger voltage lower than that provided by the prior arts. The present invention improves the ESD performance of an ESD protection device, such as a MOSFET or bipolar transistor, which is provided for protecting the power bus or IC pins during an ESD event.
Claims36
An electrostatic discharge (ESD) protection structure for an integrated circuit constructed on a substrate of a first type, comprising:
- an ESD protection means constructed on the substrate;
- an oscillation means having an output terminal for generating an oscillation signal of a first voltage polarity during an ESD event;
- a pulse-generator means, responsive to the oscillation signal, for generating electric pulses including at least pulses of a second voltage polarity opposite to said first voltage polarity during the ESD event;
- a minority-carrier injection means, having an input terminal adapted to receive said electric pulses, for injecting minority carriers into the substrate which triggers turn-on of the ESD protection means to conduct a large current due to the ESD event.
A method for triggering an electrostatic discharge (ESD) protection circuit for an integrated circuit constructed on a substrate of a first type, the ESD protection circuit including an ESD protection means constructed on the substrate, comprising the following steps:
- generating an oscillation signal of a first voltage polarity during an ESD event;
- generating, responsive to the oscillation signal, electric pulses including at least pulses of a second voltage polarity opposite to said first voltage polarity;
- applying said electric pulses to a minority-carrier injection means for injecting minority carriers into the substrate which triggers the turn-on of the ESD protection means to conduct a large current due to the ESD event.
Dependencies are inferred from the claim text.