Sensor integrated circuits and methods for safety critical applications
A sensor integrated circuit includes at least two processing channels responsive to the same or different analog input signals to generate respective processed signals. The two processing channels are non-homogenous and, in some embodiments have different processing accuracies. A checker circuit receives the first and second processed signals and is configured to detect a fault in the sensor integrated circuit when the first and second processed signals differ from each other by more than a predetermined amount.
1. A sensor integrated circuit comprising:
a first processing channel responsive to a first analog signal to generate a first processed signal, wherein the first analog signal is provided by a first type of sensing element;
a second processing channel responsive to a second analog signal to generate a second processed signal, wherein the second processing channel is non-homogenous with respect to the first processing channel, and wherein the second analog signal is provided by a second type of sensing element that is different than the first type of sensing element; and
a checker circuit responsive to the first processed signal and the second processed signal and configured to detect a fault in the sensor integrated circuit and generate a fault signal indicative of the fault when the first processed signal and the second processed signal differ from each other by more than a predetermined amount, wherein the checker circuit comprises a first sample circuit configured to sample the first processed signal and generate a first sampled signal, a second sample circuit configured to process the second processed signal and generate a second sampled signal, and a window comparator responsive to the first sampled signal and the second sampled signal and configured to generate the fault signal.
2. The sensor integrated circuit of claim 1 , wherein the first type of sensing element and the second, different type of sensing element comprise one or a combination of more than one of optical sensing elements, pressure sensing elements, or magnetic field sensing elements.
3. The sensor integrated circuit of claim 1 wherein the first processing channel has a first accuracy and the second processing channel has a second accuracy different than the first accuracy.
4. The sensor integrated circuit of claim 1 wherein the first processing channel comprises at least one different circuit element than the second processing channel.
5. The sensor integrated circuit of claim 1 wherein the first processing channel comprises a circuit to generate the first processed signal according to a first sensing methodology and the second processed signal comprises a second circuit to generate the second processed signal according to a second sensing methodology that is different than the first sensing methodology.
6. The sensor integrated circuit of claim 1 further comprising a single semiconductor die configured to support the first processing channel, the second processing channel, and the checker circuit.
7. A sensor integrated circuit comprising:
a first processing channel responsive to a first analog signal to generate with a first accuracy a first processed signal; wherein the first analog signal is provided by a first type of sensing element;
a second processing channel responsive to a second analog signal to generate with a second accuracy a second processed signal, wherein the second accuracy is different than the first accuracy, and wherein the second analog signal is provided by a second type of sensing element that is different than the first type of sensing element; and
a checker circuit responsive to the first processed signal and the second processed signal and configured to detect a fault in the sensor integrated circuit and generate a fault signal indicative of the fault when the first processed signal and the second processed signal differ from each other by more than a predetermined amount, wherein the checker circuit comprises a first sample circuit configured to sample the first processed signal and generate a first sampled signal, a second sample circuit configured to process the second processed signal and generate a second sampled signal, and a window comparator responsive to the first sampled signal and the second sampled signal and configured to generate the fault signal.
8. The sensor integrated circuit of claim 7 , wherein the first type of sensing element and the second, different type of sensing element comprise one or a combination of more than one of optical sensing elements, pressure sensing elements, or magnetic field sensing elements.
9. The sensor integrated circuit of claim 8 further comprising:
at least one first sensing element configured to sense light, a pressure, or a magnetic field and generate the first analog signal for coupling to the first processing channel; and
at least one second sensing element configured to sense the light, the pressure, or the magnetic field and generate the second analog signal for coupling to the second processing channel.
10. The sensor integrated circuit of claim 8 wherein the first type of sensing element and the second, different type of sensing elements comprise one or more of: a Hall effect element or a magnetoresistance element.
11. The sensor integrated circuit of claim 10 wherein the first type of sensing element and the second, different type of sensing element comprise one or more of a planar Hall effect element, a vertical Hall effect element, a circular vertical Hall effect element, Indium Antimonide (InSb), a giant magnetoresistance (GMR) element, an anisotropic magnetoresistance (AMR) element, a tunneling magnetoresistance (TMR) element or a magnetic tunnel junction (MTJ) element.
12. The sensor integrated circuit of claim 7 further comprising a sensing element configured to sense a parameter and generate both the first analog signal for coupling to the first processing circuit and the second analog signal for coupling to the second processing circuit.
13. The sensor integrated circuit of claim 7 wherein the first processing channel comprises a first analog-to-digital converter configured convert the first analog signal into a first digital signal and the second processing channel comprises a second analog-to-digital converter configured to convert the second analog signal into a second digital signal.
14. The sensor integrated circuit of claim 13 wherein the first analog-to-digital converter has a first conversion accuracy and the second analog-to-digital converter has a second conversion accuracy different than the first conversion accuracy.
15. The sensor integrated circuit of claim 14 wherein the first analog-to-digital converter and the second analog-to-digital converter are different ones of a sigma-delta analog-to-digital converter, a dual slope analog-to-digital converter, and a successive approximation analog-to-digital converter.
16. The sensor integrated circuit of claim 7 further comprising:
a pulse width modulation (PWM) generator responsive to the first processed signal to generate a PWM output signal having a duty cycle related to a level of the processed signal;
a multiplexer having a first input coupled to receive the PWM output signal, a second input coupled to receive a reference signal, and an output at which a selected one of the PWM output signal and the reference signal is provided; and
a pull-down resistor coupled to the output of the multiplexer, wherein the multiplexer is controlled by the fault signal.
17. The sensor integrated circuit of claim 7 wherein the predetermined amount comprises a predetermined percentage.
18. The sensor integrated circuit of claim 7 further comprising a time delay synchronizer providing a clock signal to the first sample circuit and to the second sample circuit and to the window comparator.
19. The sensor integrated circuit of claim 7 further comprising a delay element coupled to an input of the first sample circuit and configured to delay the first processed signal for coupling to the first sample circuit.
20. The sensor integrated circuit of claim 7 wherein the checker circuit comprises a first checker circuit and wherein the sensor integrated circuit further comprises a second checker circuit responsive to the first processed signal and the second processed signal and configured to detect a fault in the sensor integrated circuit when the first processed signal and the second processed signal differ from each other by more than the predetermined amount.
21. The sensor integrated circuit of claim 7 further comprising a single semiconductor die configured to support the first processing channel, the second processing channel, and the checker circuit.
22. The sensor integrated circuit of claim 7 further comprising a first semiconductor die configured to support the first processing channel and a second semiconductor die configured to support the second processing channel and the checker circuit.
23. The sensor integrated circuit of claim 7 , wherein the sensor integrated circuit comprises a linear optical sensor, a speed sensor, or a motor controller.
24. The sensor integrated circuit of claim 7 wherein the checker circuit comprises a first checker circuit and wherein the sensor integrated circuit further comprises:
a first semiconductor die configured to support the first processing channel, the second processing channel, and the checker circuit;
a third processing channel responsive to a third analog signal to generate with the first accuracy a third processed signal;
a fourth processing channel responsive to a fourth analog signal to generate with the second accuracy a fourth processed signal;
a second checker circuit responsive to the third processed signal and the fourth processed signal and configured to detect a fault in the sensor integrated circuit when the third processed signal and the fourth processed signal differ from each other by more than the predetermined amount; and
a second semiconductor die configured to support the third processing channel, the fourth processing channel, and the second checker circuit.
25. A sensor integrated circuit comprising:
a first processing channel responsive to a first analog signal to generate with a first accuracy a first processed signal;
a second processing channel responsive to a second analog signal to generate with a second accuracy a second processed signal, wherein the second accuracy is different than the first accuracy;
a checker circuit responsive to the first processed signal and the second processed signal and configured to detect a fault in the sensor integrated circuit and generate a fault signal indicative of the fault when the first processed signal and the second processed signal differ from each other by more than a predetermined amount, wherein the checker circuit comprises a first sample circuit configured to sample the first processed signal and generate a first sampled signal, a second sample circuit configured to process the second processed signal and generate a second sampled signal, and a window comparator responsive to the first sampled signal and the second sampled signal and configured to generate the fault signal;
at least one first sensing element configured to sense light, a pressure, or a magnetic field, and generate the first analog signal for coupling to the first processing channel; and
at least one second sensing element configured to sense the light, the pressure, or the magnetic field and generate the second analog signal for coupling to the second processing channel.
26. The sensor integrated circuit of claim 25 , wherein the at least one first sensing element and the second at least one second sensing element comprise one or a combination of more than one of optical sensing elements, pressure sensing elements, or magnetic field sensing elements.
27. The sensor integrated circuit of claim 26 wherein the at least one first sensing element and the at least one second sensing element comprise different types of sensing elements.
28. The sensor integrated circuit of claim 27 wherein the different types of sensing elements comprise one or more of: a Hall effect element or a magnetoresistance element.
29. The sensor integrated circuit of claim 28 wherein the different types of sensing elements comprise one or more of a planar Hall effect element, a vertical Hall effect element, a circular vertical Hall effect element, Indium Antimonide (InSb), a giant magnetoresistance (GMR) element, an anisotropic magnetoresistance (AMR) element, a tunneling magnetoresistance (TMR) element or a magnetic tunnel junction (MTJ) element.