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An apparatus includes an electrostatic discharge (ESD) protection device. In one embodiment, the protection device electrically coupled between a first node and a second node of an internal circuit to be protected from transient electrical events. The protection device includes a bipolar device or a

An apparatus includes an electrostatic discharge (ESD) protection device. In one embodiment, the protection device electrically coupled between a first node and a second node of an internal circuit to be protected from transient electrical events. The protection device includes a bipolar device or a silicon-controlled rectifier (SCR). The bipolar device or SCR can have a modified structure or additional circuitry to have a selected holding voltage and/or trigger voltage to provide protection over the internal circuit. The additional circuitry can include one or more resistors, one or more diodes, and/or a timer circuit to adjust the trigger and/or holding voltages of the bipolar device or SCR to a desired level. The protection device can provide protection over a transient voltage that ranges, for example, from about 100 V to 330V.

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1. An apparatus comprising: an internal circuit electrically coupled between a first node and a second node; anda protection device electrically coupled between the first node and the second node, wherein the protection device is configured to protect the internal circuit from transient electrical e

1. An apparatus comprising: an internal circuit electrically coupled between a first node and a second node; anda protection device electrically coupled between the first node and the second node, wherein the protection device is configured to protect the internal circuit from transient electrical events, the protection device comprising: a silicon-controlled rectifier (SCR) having an anode, a gate, and a cathode, wherein the anode is electrically coupled to the first node, and the cathode is electrically coupled to the second node,wherein the SCR comprises: a substrate having a doping of a first type;a first well disposed in a first upper portion of the substrate, and having a doping of a second type different from the first type;a second well disposed in a second upper portion of the substrate, and spaced apart laterally from the first well such that a third upper portion of the substrate is laterally interposed between the first and second wells, the second well having a doping of the second type, the third upper portion having a doping of the first type;a first region disposed in a top portion of the first well, and having a doping of the second type with a higher doping concentration than that of the first well, the first region being electrically coupled to the second node;a second region disposed in a top portion of the second well, and having a doping of the second type with a higher doping concentration than that of the second well;a third region disposed in the first well adjacent to the first region such that the third region is interposed laterally between the first region and the third upper portion of the substrate, the third region having a doping of the first type with a higher doping concentration than that of the substrate;a fourth region disposed in the second well adjacent to the second region such that the fourth region is interposed laterally between the second region and the third upper portion of the substrate, the fourth region having a doping of the first type with a higher doping concentration than that of the substrate, the fourth region being electrically coupled to the first node; anda gate contact disposed on the third upper portion of the substrate. 2. The apparatus of claim 1, wherein the SCR comprises: a PNP bipolar transistor having an emitter, a base, and a collector, wherein the emitter of the PNP bipolar transistor is electrically coupled to the first node, wherein the collector of the PNP bipolar transistor forms the gate of the SCR; andan NPN bipolar transistor having an emitter, a base, and a collector, wherein the emitter of the NPN bipolar transistor is electrically coupled to the second node, wherein the base of the NPN bipolar transistor is electrically coupled to the collector of the PNP bipolar transistor, wherein the collector of the NPN bipolar transistor is electrically coupled to the base of the PNP bipolar transistor. 3. The apparatus of claim 1, further comprising: a diode array comprising a plurality of diodes connected in series between the gate and the anode of the silicon-controlled rectifier and arranged such that the diodes conduct a current into the SCR to turn on the SCR when the diodes break down. 4. The apparatus of claim 1, the protection device further comprising: a resistor electrically coupled between the gate and the cathode of the SCR. 5. The apparatus of claim 1, wherein the third region has a lateral dimension extending in a direction from the first region toward the third upper portion of the substrate, wherein the lateral dimension of the third region is greater than the lateral dimension of the first region in the direction. 6. The apparatus of claim 5, wherein the fourth region has a lateral dimension extending in the direction, wherein the lateral dimension of the fourth region is greater than the lateral dimension of the second region in the direction. 7. The apparatus of claim 1, the protection device further comprising: a first resistor electrically coupled between the cathode of the SCR and the second node; anda second resistor electrically coupled to the gate of the SCR. 8. The apparatus of claim 7, wherein the first resistor comprises: a first coil having a first end electrically coupled to the cathode of the SCR, wherein the first coil spirals towards the center of the first coil in one of clockwise or anti-clockwise direction; anda second coil underlying the first coil and having a second end electrically coupled to the second node, wherein the second coil spirals towards the center of the second coil in the other of clockwise or anti-clockwise direction, wherein the centers of the first and second coils are electrically coupled to each other. 9. The apparatus of claim 1, wherein: the SCR comprises a bipolar device having a first terminal configured to serve as the anode, a second terminal configured to serve as the gate, and a third terminal configured to serve as the cathode, andthe protection device further comprises: an impedance block electrically coupled between the second terminal of the bipolar device and a first voltage reference, wherein the impedance block is configured to have a varying impedance; andan impedance control circuit configured to vary the impedance of the impedance block. 10. The apparatus of claim 9, wherein the impedance block comprises a plurality of transistors electrically coupled in parallel to one another, and coupled between the second terminal of the bipolar device and the first voltage reference. 11. The apparatus of claim 10, wherein the impedance control circuit comprises a timer circuit configured to delay a decrease in the impedance of the impedance block upon an occurrence of an overvoltage condition between the first node and the second node. 12. The apparatus of claim 11, wherein the timer circuit comprises: a timer capacitor electrically coupled between a second voltage reference and a timer node; anda timer resistor electrically coupled between the timer node and the third terminal of the bipolar device,wherein the timer node is electrically coupled to the impedance block. 13. The apparatus of claim 12, wherein the plurality of transistors comprise MOS transistors, each of the MOS transistors having a gate, and wherein the timer node is electrically coupled to the gates of the MOS transistors. 14. The apparatus of claim 13, wherein the timer circuit is configured to delay turning on the MOS transistors by a time constant that is substantially equal to the capacitance of the timer capacitor times the resistance of the timer resistor. 15. The apparatus of claim 9, further comprising a first resistor electrically coupled between the third terminal of the bipolar device and a third voltage reference. 16. The apparatus of claim 15, further comprising: a second resistor electrically coupled between the second terminal of the bipolar device and ground; anda voltage source electrically coupled to the first terminal of the bipolar device.