Memory circuit using a reference for sensing
View Patent ↗A memory includes a plurality of memory cells, a sense amplifier coupled to at least one of the plurality of memory cells, a temperature dependent current generator comprising a plurality of selectable temperature dependent current sources for generating a temperature dependent current, a temperature independent current generator comprising a plurality of selectable temperature independent current sources for generating a temperature independent current, and a summer coupled to the temperature dependent current generator and the temperature independent current generator for combining the temperature dependent current and the temperature independent current to generate a reference current for use by the sense amplifier. A temperature coefficient of the reference current is approximately a same as a temperature coefficient of a memory cell current of at least one of the plurality of memory cells.
1. A memory comprising:
a plurality of memory cells;
a sense amplifier coupled to at least one of the plurality of memory cells;
a reference current generator coupled to generate a reference current for the sense amplifier, the reference current generator generating a temperature dependent current and a temperature independent current, the reference current generator generating the reference current from both the temperature dependent current and the temperature independent current, wherein the reference current generator comprises a current scaler coupled to the reference current generator, the current scaler scaling the reference current to a predetermined current value; and
a comparator coupled to the current scaler, the comparator comparing an external current to the reference current.
2. The memory of claim 1 , wherein a temperature coefficient of the reference current is approximately a same as a temperature coefficient of a current of the at least one memory cell with respect to temperature.
3. The memory of claim 1 , wherein the current scaler comprises a plurality of selectable temperature dependent current sources for generating the temperature dependent current.
4. The memory of claim 3 , wherein a rate of change of current with respect to temperature of the temperature dependent current depends on what number of the plurality of selectable temperature dependent current sources are selected.
5. The memory of claim 3 , wherein the plurality of selectable current sources comprises a first bipolar transistor and a second bipolar transistor having a different area than the first bipolar transistor.
6. The memory of claim 1 , wherein the rate of change of current with respect to temperature of the temperature dependent current is approximately a same as a rate of change of current with respect to temperature of a current of the memory cell.
7. The memory of claim 1 , wherein the current scaler comprises a plurality of selectable temperature independent current sources for generating the temperature independent current, wherein a level of the temperature independent current depends on what number of the plurality of selectable temperature independent current sources are selected.
8. The memory of claim 7 , wherein the selectable temperature independent current sources comprises a bandgap current reference.
9. A method for generating a reference current for a memory, comprising:
generating a temperature dependent current, the temperature dependent current having a rate of change of current with respect to temperature which represents a rate of change of current with respect to temperature of a memory cell current of the memory;
generating a temperature independent current;
combining the temperature dependent current and the temperature independent current to generate a reference current for use by a sense amplifier of the memory; and
comparing the attenuated reference current to an external current to determine if the attenuated reference current matches the predetermined current value.
10. The method of claim 9 , wherein the reference current has a temperature coefficient that is approximately a same as a temperature coefficient of the memory cell current.
11. The method of claim 9 , further comprising:
prior to providing the reference current for use by the sense amplifier, scaling the reference current to a predetermined current value.
12. The method of claim 9 , wherein generating the temperature dependent current comprises selecting one or more selectable temperature dependent current sources to generate the temperature dependent current.
13. The method of claim 9 , wherein generating the temperature independent current comprises selecting one or more selectable temperature independent current sources to generate the temperature independent current.
14. The method of claim 9 , wherein the generated reference current is not generated by a reference memory cell of the memory.