Reference sense amplifier for non-volatile memory
One or more sense amplifiers for sensing the conduction current of non-volatile memory is controlled by signals that are timed by a reference sense amplifier having similar characteristics and operating conditions. In one aspect, a sensing period is determined by when the reference sense amplifier sensing a reference current detects an expected state. In another aspect, an integration period for an amplified output is determined by when the reference sense amplifier outputs an expected state. When these determined timings are used to control the one or more sense amplifiers, environment and systemic variations are tracked.
1. A memory comprising:
a sensing circuit for sensing the current relative to a reference current, said sensing circuit receiving a first timing signal to sense the current over a predetermined period to produce either first or second signal depending respectively on whether the sensed current is greater or less than the reference current;
wherein said first timing signal is provided by a reference sensing circuit having substantially similar characteristic and operating conditions as the sensing circuit;
said reference sensing circuit sensing the reference current for a sufficient period to have its output change signal between first and second signals; and
said reference sensing circuit timing the predetermined period by the sufficient period.
2. The memory as in claim 1 , wherein the sensing circuit is one of a plurality of similar sensing circuits operating in parallel, and the determined sensing period is used to time the predetermined period of each of the plurality of sensing circuits.
3. The memory as in claim 1 , wherein the sensing circuit includes:
a capacitor for the current to discharge over the predetermined period; and
a comparator to compare a resultant voltage from the discharge with a reference voltage.
4. The memory as in claim 1 , wherein the similar operating conditions includes temperature.
5. The memory as in claim 1 , wherein the similar operating conditions includes power supply.
6. The memory as in claim 1 , wherein the similar operating conditions includes manufacturing process.
7. The memory as in claim 3 , wherein the sensing circuit further includes:
an amplifier that amplifies the resultant voltage for a predetermined integration period of time to obtain an output.
8. A memory comprising:
a sensing circuit for sensing the current relative to a reference current, said sensing circuit including an internal node with first or second voltage level depending respectively on whether the sensed current is greater or less than the reference current; an amplifier to amplify the voltage on the internal node to produce an output, said output having either first or second signal when respectively first or second voltage level are amplified over a predetermined integration period;
wherein said integration period is provided by a reference sensing circuit having substantially similar characteristic and operating conditions as the sensing circuit;
said reference sensing circuit sensing the reference current and amplifying the voltage level on its corresponding internal node for a sufficient integration period to have its output change signal between first and second signals; and
said reference sensing circuit timing the predetermined integration period by the sufficient integration period.
9. The memory as in claim 8 , wherein the sensing circuit is one of a plurality of similar sensing circuits operating in parallel, and the determined sensing period is used to time the predetermined period of each of the plurality of sensing circuits.
10. The memory as in claim 8 , wherein the sensing circuit includes:
a capacitor for the current to discharge over the predetermined period; and
a comparator to compare a resultant voltage from the discharge with a reference voltage.
11. The memory as in claim 8 , wherein the similar operating conditions includes temperature.
12. The memory as in claim 8 , wherein the similar operating conditions includes sharing a power supply.
13. The memory as in claim 8 , wherein the similar operating conditions includes being in the same manufacturing process.
14. The memory as in any one of claims 1 to 13 , wherein the current being sensed is the conduction current of a memory storage unit.
15. The memory as in claim 14 , wherein the memory storage unit is one of a plurality of memory storage units.
16. The memory as in claim 15 , wherein the plurality of memory storage units are flash EEPROM.
17. The memory as in claim 16 , wherein each memory storage unit stores one bit of data.
18. The memory as in claim 16 , wherein each memory storage unit stores more than one bit of data.