Method for providing a power on reset signal with a quadratic current compared to an exponential current
View Patent ↗Aspects of the present invention include a method, apparatus and device for generating a power on reset (POR) signal in relation to the crossing point of two currents wherein at least one current is a quadratic function and the other is an exponential function, where each has a mathematical correlation to a function of a predetermined power supply voltage.
1. A power on reset (POR) circuit comprising:
a voltage supply terminal receiving a voltage power supply,
a first current generator providing a first current source in relation to a first mathematical formulation being a quadratic function of said voltage power supply,
a second current generator providing a second current source in relation to a second mathematical formulation being an exponential function of said voltage power supply,
a current comparator for comparing said first current source with said second current source at a predetermined supply voltage, and
a POR signal generator for generating a logical signal as output in relation to said current comparator.
2. The circuit of claim 1 wherein the quadratic function of said voltage power supply is square of said voltage power supply, (V SUPP ) 2 .
3. The circuit of claim 1 wherein the exponential function of said voltage power supply is exp(V SUPP ).
4. The circuit of claim 3 wherein said first mathematical formulation is a function of the square of said voltage power supply, (V SUPP ) 2 , and said current comparator compares said first and second current source in relation to a predetermined power supply voltage value.
5. The circuit of claim 4 wherein predetermined power supply voltage value is at a predetermined crossing point.
6. The circuit of claim 5 wherein a logical HIGH results if said crossing point has not been attained.
7. The circuit of claim 5 wherein a logical LOW results if said crossing point has been attained.
8. The circuit of claim 1 further comprising a buffer.
9. The circuit of claim 8 wherein said buffer is a simple inverter and said POR signal generator generates a full chip reset signal.
10. The circuit of claim 1 wherein, a first current generator is a vertical pnp device, said second current generator is a nmos transistor.
11. An integrated circuit having a power on reset (POR) circuit, the integrated circuit comprising:
a voltage power supply,
a first current source being a quadratic function of said voltage power supply,
a second current source being an exponential function of said voltage power supply,
a current comparator for comparing said first current source with said second current source at a predetermined supply voltage,
a buffer, and
a POR signal generator for generating a logical signal in relation to a crossing point that is determined when said first current source crosses said second current source.
12. The integrated circuit of claim 11 wherein the POR circuit provides power supply voltage monitoring.
13. The integrated circuit of claim 11 wherein the POR circuit is configured such that said first current source has a first value when said first current source crosses said second current source and has a second value greater than the first value after said first current source crosses said second current source, and such that said second current source has a third value when said first current source crosses said second current source and has a fourth value greater than the third value after said first current source crosses said second current source.
14. An apparatus having a power on reset (POR) circuit, the apparatus comprising:
a voltage power supply capable of ramping upwards or downwards as a function of time,
a first current source being a quadratic function of said voltage power supply,
a second current source being an exponential function of said voltage power supply,
a current comparator for comparing said first current source with said second current source at a predetermined supply voltage and generating a logical signal as output,
wherein, a crossing point occurs when said first current source crosses said second current source and said logical signal is generated in relation to said power supply voltage in relation to said crossing point.
15. The apparatus of claim 14 wherein said logical signal is generated at the predetermined supply voltage.
16. The apparatus of claim 15 , wherein the logical signal has a value of HIGH during power supply voltage ramping at start up of said apparatus.
17. The apparatus of claim 14 wherein the POR circuit is configured such that said first current source has a first value when said first current source crosses said second current source and has a second value greater than the first value after said first current source crosses said second current source, and such that said second current source has a third value when said first current source crosses said second current source and has a fourth value greater than the third value after said first current source crosses said second current source.
18. A computing device having a power on reset (POR) circuit, the computing device comprising:
a voltage supply terminal receiving a voltage power supply,
a first current generator providing a first current source in relation to a first mathematical formulation being a quadratic function of said voltage power supply,
a second current generator providing a second current source in relation to a mathematical formulation being an exponential functional of said voltage power supply,
a current comparator for comparing said first current source with said second current source at a predetermined supply voltage, and for generating a logical signal as output,
wherein, a crossing point occurs where said first current source crosses said second current source and said logical signal is generated in relation to power supply voltage in relation to said crossing point.
19. The device of claim 18 wherein said first mathematical formulation is a quadratic function of the square of said voltage power supply, (V SUPP ) 2 , said second mathematical formulation is exp(V SUPP ), and said current comparator compares said first and second current source in relation to a predetermined power supply voltage value.
20. The device of claim 19 , wherein said power supply voltage is at a period of time during start up of said device.
21. A method comprising:
providing power from a voltage power supply,
generating a first current source from a first current generator in relation to a first mathematical formulation being a quadratic function of said voltage power supply,
generating a second current source from a second current generator in relation to a second mathematical formulation being an exponential function of said voltage power supply,
ramping said voltage power supply comparing said first current source with said second current source at a predetermined supply voltage, and
generating a logical signal as an output POR signal in relation to said comparing step.
22. The method of claim 21 , wherein said first mathematical formulation is a function of the square of said voltage power supply, (V SUPP ) 2 .
23. The method of claim 22 , wherein said second mathematical formulation is a direct function of the exponential of said voltage power supply, exp(V SUPP ).
24. The method of claim 21 , wherein said second mathematical formulation is a direct function of the exponential of said voltage power supply, exp(V SUPP ).
25. The method of claim 21 , wherein said ramping causes said first current source to be greater than said second current source at a predetermined time.
26. The method of claim 25 , wherein said logical signal generated as an output POR signal is HIGH.
27. The method of claim 21 , wherein said ramping causes said first current source to be lesser than said second current source at a predetermined time.
28. The method of claim 27 , wherein said logical signal generated as an output POR signal is LOW.
29. The method of claim 21 , wherein said ramping causes said first current source to be identical to said second current source at a predetermined time at a crossing point threshold.
30. The method of claim 21 wherein said first current source has a first value when said first current source crosses said second current source and a second value greater than the first value after said first current source crosses said second current source, and wherein said second current source has a third value when said first current source crosses said second current source and a fourth value greater than the third value after said first current source crosses said second current source.
31. A computing system having a circuit for generating a power on reset (POR), wherein generating comprises:
providing power from a voltage power supply,
generating a first current source from a first current generator in relation to a first mathematical formulation being a quadratic function of said voltage power supply,
generating a second current source from a second current generator in relation to a second mathematical formulation being an exponential function of said voltage power supply, ramping said voltage power supply comparing said first current source with said second current source at a predetermined supply voltage, and
generating a logical signal as an output POR signal in relation to said comparing step,
wherein said first mathematical formulation is a function of the square of said voltage power supply, (V SUPP ) 2 , said second mathematical formulation is a function of the exponential of said voltage power supply, exp(V SUPP ).
32. A computing device having a power on reset (POR) circuit for generating a reset signal wherein the generating comprises:
providing power from a voltage power supply at start-up and for a predetermined period of time thereafter,
generating a first current source from a first current generator in relation to a first mathematical formulation being a function of the square of said voltage power supply, (V SUPP ) 2 ,
generating a second current source from a second current generator in relation to a second mathematical formulation being a function of the exponential of said voltage power supply, exp(V SUPP ),
ramping said voltage power supply from said start-up to said predetermined period,
comparing said first current source with said second current source at a predetermined supply voltage,
generating a logical signal as an output POR signal in relation to said comparing step, and
buffering said POR signal using an inverter.
33. The computing device of claim 32 being a computer.