Circuit and method for supplying programming potential at voltages larger than BVDss of programming transistors
View Patent ↗A circuit for programming an antifuse coupled between a first node and a second node includes at least one transistor for supplying a programming potential V PP to the first node. A first transistor has a source coupled to a third node switchably coupleable between a potential of V PP /2 and ground potential, a drain, and a gate. A second transistor has a source coupled to the drain of the first transistor, a drain coupled to the second node, and a gate. Programming circuitry is coupled to the gate of the first transistor and the gate of the second transistor and configured to in a programming mode apply a potential of either zero volts or VPP/2 to the gate of the first transistor and to apply a potential of VPP/2 to the gate of the second transistor. The first and second transistors have a BVDss rating of not more than about V PP /2.
1. A circuit for applying current to a device having a first node and a second node with a potential V PP , the circuit disposed on an integrated circuit and comprising:
a first transistor having a first node coupled to a third node switchably coupleable between a potential of about V PP/2 and ground potential, a second node, and a gate;
a second transistor having a first node coupled to said second node of said first transistor, a second node coupled to the second node of the antifuse, and a gate;
a bootstrap circuit coupled to and programmably capable of precharging the first node of the device to a selected potential of V PP or V PP 2; and
circuitry coupled to said gate of said first transistor and said gate of said second transistor and configured to, in a current-applying mode, apply a potential of either zero volts or about V PP/2 to said gate of said first transistor and to apply a potential of about V PP/2 to said gate of said second transistor.
2. The circuit of claim 1 wherein:
the first node and second node are located off of the integrated circuit and the device is an external device.
3. The circuit of claim 1 wherein:
the first node of the device is connected to a wiring track;
the second node of the device is connected to a circuit input track; and
the second node of the first transistor and the first node of said second transistor are coupled to a circuit input associated with the circuit input track.
4. The circuit of claim 1 wherein:
the first node of the device is connected to a first wiring track and the second node of the device is connected to a second wiring track.
5. The circuit of claim 1 further including:
a circuit output track coupled to a circuit output through an output isolation transistor and to the second wiring track through a second device; and
a fifth transistor having a first node coupled to a fourth node switchably coupleable between a potential of V PP/2 and ground, a second node coupled to the circuit output track, and a gate coupled to the programming circuitry, the programming circuitry further configured to in a programming mode selectively turn on the fifth transistor.
6. The circuit of claim 1 further including:
a circuit input track coupled to a circuit input through an input isolation transistor and to the second wiring track through a third device; and
a sixth transistor having a first node coupled to a fifth node switchably coupleable between a potential of VPP/2 and ground, a second node coupled to the circuit input track, and a gate coupled to the programming circuitry, the programming circuitry further configured to in a programming mode selectively turn on the sixth transistor.
7. The circuit of claim 6 wherein:
the circuit input is an input to an inverter comprising:
an inverter transistor of a first type having a first node connected to a first power supply potential, a second node, and a gate,
an inverter transistor of a second type having a first node connected to the second node of the inverter transistor of the first type, a gate connected to the gate of the inverter transistor of the first type, and a first node; and
wherein the circuit further includes:
a transistor of the first type having a first node connected to the first node of the inverter transistor of the first type, a second node connected to the second node of the inverter transistor of the second type, and a gate coupled to the programming circuitry;
a transistor of the second type having a second node connected to the first node of the n-channel MOS inverter transistor of the second type, a first node coupled to ground, and a gate coupled to the programming circuitry.
8. The circuit of claim 7 wherein:
a transistor of the first type is a p-channel MOS transistor; and
a transistor of the second type is an n-channel MOS transistor.
9. The circuit of claim 1 wherein:
the bootstrap circuit is formed from a third transistor having a first node coupled to the first node of the antifuse, a second node coupled to a node selectively carrying the potential V PP or the potential V PP /2, and a gate, and a fourth transistor having a first node coupled to the gate of the third transistor, a second node coupled to a precharge select node, and a gate coupled to a programming control node.
10. The circuit of claim 1 wherein:
the first transistor and the second transistor are n-channel MOS transistors.