| 摘要 |
A high voltage protection circuit (20) in a non-volatile memory includes a first transistor (22) and a second transistor (24) each formed in their own separate wells. A high voltage supply (Vhv) is provided at the drain of the second transistor (24). The source (40) of second transistor (24) is connected to the drain of first transistor (22) and to well (32), and the gate of the second transistor (24) is connected to Vdd, the main power supply to the chip. By forming the transistors in their own separate wells with the source of the second transistor (24) connected to its own well, breakdown of the circuit is governed by the sum of BVdss of the first transistor (22) and a gate induced breakdown (BVind) of the second transistor (24). With this circuit use of even a low Vdd (e.g. <3V) on the gate of the second transistor (24) is sufficient to protect against unwanted exposure to Vhs or to prevent leakage so that a higher stand-off voltage need not be generated and routed to the circuit.
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