Memory device for protecting memory cells during programming
Improved circuitry and methods for programming memory cells of a memory device are disclosed. The improved circuitry and methods operate to protect the memory cells from potentially damaging electrical energy that can be imposed during programming of the memory cells. Additionally, the improved circuitry and methods operate to detect when programming of the memory cells has been achieved. The improved circuitry and methods are particularly useful for programming non-volatile memory cells. In one embodiment, the memory device pertains to a semiconductor memory product, such as a semiconductor memory chip or a portable memory card.
1. A memory device having an array of memory elements accessible via at least one bitline and at least one wordline, comprising:
a first field-effect transistor having first, second and third terminals, the first terminal connected to a first potential;
a second field-effect transistor having first, second and third terminals, the first terminal connected to the second terminal of said first field-effect transistor, and the second terminal connected to a bitline;
a memory element connected to a wordline and to the bitline;
a third field-effect transistor having first, second and third terminals, the first terminal connected to the first potential, the second terminal connected to a first node, and the third terminal connected to the third terminal of the first field-effect transistor;
a fourth field-effect transistor having first, second and third terminals, the first terminal connected to the first node, the second terminal connected to a second potential;
a fifth field-effect transistor having first, second and third terminals, the first terminal connected to a first current source, the second terminal connected to the second potential, and the third terminal is connected to the third terminal of the fourth field-effect transistor, the first terminal further being connected to the third terminal;
a sixth field-effect transistor having first, second and third terminals, the first terminal connected to the first potential, the second terminal connected to a second node, and the third terminal connected to the third terminal of the first field-effect transistor;
a seventh field-effect transistor having first, second and third terminals, the first terminal connected to the second node, the second terminal connected to the second potential;
an eighth field-effect transistor having first, second and third terminals, the first terminal connected to a second current source, the second terminal connected to the second potential, and the third terminal is connected to the third terminal of the seventh field-effect transistor, the first terminal further being connected to the third terminal;
program control circuitry connected to the second node; and
a ninth field-effect transistor having first, second and third terminals, the first terminal connected to the first potential, the second terminal connected to the third terminal of the first field-effect transistor, and the third terminal connected to the program control circuitry,
wherein the third terminal of the second field-effect transistor is connected to the first node.
2. A memory device as recited in claim 1 , wherein said memory device further comprises:
a tenth field-effect transistor having first, second and third terminals, the first terminal connected to the first potential, the second terminal connected to a third current source, the third terminal connected to the second terminal of the first field-effect terminal, and the second terminal further being connected to the third terminal of the first field-effect transistor.
3. A memory device as recited in claim 1 , wherein said first, second, third, sixth and ninth field-effect transistors are PMOS devices, and wherein said fourth, fifth, seventh and eighth field-effect transistors are NMOS devices.
4. A memory device as recited in claim 1 , wherein the memory element is a non-volatile memory element.
5. A memory device as recited in claim 4 , wherein said non-volatile memory element is a diode-based memory element.
6. A memory device as recited in claim 4 , wherein said non-volatile memory element is an antifuse device.