Input pin state detection circuit and method therefor
AssigneeNXP B.V.
InventorsDominicus M. Roozeboom, Sharad Murari, Harold Garth Hanson
Life of this patent
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Abstract
A state-detection circuit facilitates the detection of the state of an input pin relative to several different types of input circuits. According to an example embodiment, a state-detection circuit includes a plurality of comparators and circuit components, configured to provide a plurality of binary output signals that collectively indicate a state of an input pin to which the comparators are coupled. The state-detection circuit is configured to facilitate the detection of several different types of input circuits, based upon the binary output signals.
Claims20
An input state detection circuit comprising:
- an input pin configured for receiving signals generated by a plurality of different types of input circuits;
- a state-detection circuit configured to provide an output characterizing the state of the input pin for a plurality of input states respectively corresponding to the plurality of different types of input circuits, the state-detection circuit having
- a plurality of comparators respectively having their high-level inputs directly coupled to the input pin, having their low-level inputs coupled between a power source and a ground node, and configured to provide a binary output that, when collectively processed with the binary outputs of the other comparators, indicates the state of the input pin,
- a resistor circuit connected in series between a first one of the comparators and the power source,
- for each pair of comparators having input pins connected in series, a resistor circuit connected therebetween,
- a resistor circuit connected between a last one of the comparators and the ground node;
- a negative-feedback operational amplifier having an output connected to the high-level input of the comparators, having a high-level input, a low-level input and a feedback circuit connecting the output to the low-level input;
- a resistor circuit connected between the high-level input of the negative-feedback operational amplifier and a feedback power source;
- and
- a resistor circuit connected between the high-level input of the negative-feedback operational amplifier and a feedback ground node.
A configurable input circuit for operating in accordance with a plurality of different input circuits, the input circuit comprising:
- an input pin to receive an input signal;
- a state-detection circuit configured to, upon start-up of the configurable input circuit, provide a binary output signal for determining a state characteristic of the input signal, the state detection circuit having an output that provides at least N−1 output values that make up the binary output signal, the output signal being responsive to the state of the input pin and exclusive for each of N different types of input circuits, wherein N is an integer greater than two;
- a decoder circuit configured to decode the binary output to determine the state of the input pin and a type of input circuit corresponding to the determined state;
- and
- a control circuit configured to power-on the state-detection circuit upon startup of the configurable input circuit, to power-off the state-detection circuit in response to the decoder circuit determining the state of the input signal, and to configure the input circuit for operation based upon the determined state of the input pin.
A method for operating an input circuit, the method comprising:
- receiving an input signal at an input pin;
- in response to a startup condition, powering a state-detection circuit to provide a binary output signal for determining a state characteristic of the input signal, the state detection circuit providing an output having at least N−1 output values that make up the binary output signal, the output signal being responsive to the state of the input pin and exclusive for each of N different types of input circuits;
- in a decoder circuit, decoding the binary output to determine the state of the input pin and a type of input circuit corresponding to the determined state;
- and
- in response to determining the state of the input signal, power-off the state-detection circuit.
Dependencies are inferred from the claim text.