Current matching circuitry
An over-current protection sensor circuit is disclosed. The circuit includes: a reference current source, configured to source a reference current; a reference MOS transistor, configured to receive the reference current and a gate voltage, and to generate a reference drain voltage based at least in part on the reference current and the gate voltage; an operational amplifier, configured to receive a reference voltage and to generate the gate voltage based on a difference between the reference voltage and the reference drain voltage; an output MOS transistor, configured to receive an input current and the gate voltage, and to generate an output drain voltage based at least in part on the input current and the gate voltage; and a comparator, configured to generate an over-current signal based on a difference between the reference drain voltage and the output drain voltage.
1 . An over-current protection sensor circuit, comprising:
a reference current source configured to source a reference current;
a reference MOS transistor configured to:
receive the reference current and a gate voltage, and
generate a reference drain voltage based on the reference current and the gate voltage;
an operational amplifier configured to:
receive a reference voltage, and
generate the gate voltage based on a difference between the reference voltage and the reference drain voltage;
an output MOS transistor having an effective width that is a factor k times an effective width of the reference MOS transistor, the output MOS transistor configured to:
receive an input current and the gate voltage, and
generate an output drain voltage based on the input current and the gate voltage; and
a comparator configured to generate an over-current signal based on a difference between the reference drain voltage and the output drain voltage.
2 . The over-current protection sensor circuit of claim 1 , wherein the over-current signal indicates whether the input current is greater than a threshold current.
3 . The over-current protection sensor circuit of claim 1 , wherein the factor k is programmable.
4 . The over-current protection sensor circuit of claim 1 , wherein the over-current signal indicates whether the input current is greater than a threshold current, and wherein the threshold current is k times the reference current.
5 . The over-current protection sensor circuit of claim 4 , wherein the factor k is programmable.
6 . The over-current protection sensor circuit of claim 1 , wherein the reference MOS transistor comprises a selected one of a plurality of redundant reference MOS transistors.
7 . The over-current protection sensor circuit of claim 1 , wherein the over-current signal indicates whether the input current is greater than a threshold current, and wherein, in response to the input current being equal to the threshold current, a drain to source voltage of the reference MOS transistor is equal to a drain to source voltage of the output MOS transistor.
8 . An electrical system, comprising:
a controller;
a current sourcing circuit; and
an over-current protection sensor circuit, comprising:
a reference current source configured to source a reference current;
a reference MOS transistor configured to:
receive the reference current and a gate voltage, and
generate a reference drain voltage based on the reference current and the gate voltage;
an operational amplifier configured to:
receive a reference voltage, and
generate the gate voltage based on a difference between the reference voltage and the reference drain voltage;
an output MOS transistor having an effective width that is a factor k times an effective width of the reference MOS transistor, the output MOS transistor configured to:
receive an input current and the gate voltage, and
generate an output drain voltage based on the input current and the gate voltage; and
a comparator configured to generate an over-current signal based on a difference between the reference drain voltage and the output drain voltage.
9 . The electrical system of claim 8 , wherein the current sourcing circuit comprises a laser.
10 . The electrical system of claim 8 , wherein the over-current signal indicates whether the input current to the over-current protection sensor circuit is greater than a threshold current.
11 . The electrical system of claim 10 , wherein the controller is configured to:
receive the over-current signal, and
generate a control signal that causes the current sourcing circuit to cease operation in response to the over-current signal indicating that the input current to the over-current protection sensor circuit is greater than the current threshold.
12 . The electrical system of claim 8 , wherein the factor k is programmable.
13 . The electrical system of claim 8 , wherein the over-current signal indicates whether the input current is greater than a threshold current, wherein the threshold current is k times the reference current.
14 . The electrical system of claim 13 , wherein the factor k is programmable.
15 . The electrical system of claim 8 , wherein the reference MOS transistor comprises a selected one of a plurality of redundant reference MOS transistors.
16 . The electrical system of claim 8 , wherein the over-current signal indicates whether the input current to the over-current protection sensor circuit is greater than a threshold current, and wherein in response to the input current being equal to the threshold current, a drain to source voltage of the reference MOS transistor is substantially equal to a drain to source voltage of the output MOS transistor.
17 . A method of operating an over-current protection sensor circuit, the method comprising:
sourcing, by a reference current source, a reference current;
receiving, by a reference MOS transistor, the reference current and a gate voltage;
generating, by the reference MOS transistor, a reference drain voltage based on the reference current and the gate voltage;
receiving, by an operational amplifier, a reference voltage;
generating, by the operational amplifier, the gate voltage based on a difference between the reference voltage and the reference drain voltage;
receiving, by an output MOS transistor, an input current and the gate voltage, wherein an effective width of the output MOS transistor is a factor k times an effective width of the reference MOS transistor;
generating, by the output MOS transistor, an output drain voltage based on the input current and the gate voltage; and
generating, by a comparator, an over-current signal based on a difference between the reference drain voltage and the output drain voltage.
18 . The method of claim 17 , wherein the over-current signal indicates whether the input current is greater than a threshold current.
19 . The method of claim 18 , wherein the threshold current is k times the reference current.
20 . An overcurrent condition sense circuit, comprising:
a current source;
a reference transistor configured to:
conduct current of the current source, and
generate a reference transistor voltage based on the conducted current, the reference transistor comprising a reference gate;
an output transistor having an effective width that is a factor k times an effective width of the reference transistor, the output transistor configured to;
receive an input current, the output transistor comprising an output gate electrically connected to the reference gate, and
generate an output transistor voltage based on the input current, the output transistor voltage indicating an amount of the input current;
a difference amplifier circuit configured to generate an amplifier output signal based on a difference between the reference transistor voltage and the output transistor voltage; and
a switching network configured to select the reference transistor from a plurality of candidate reference transistors.
21 . The overcurrent condition sense circuit of claim 20 , wherein the factor k is programmable.
22 . The overcurrent condition sense circuit of claim 20 , wherein the amplifier output signal indicates whether the input current is greater than a threshold current, and wherein the threshold current is k times a current conducted by the reference transistor.