Circuitry to protect a test instrument

1. A method of controlling a test instrument; comprising:

determining a first value corresponding to power output by the test instrument;

determining a second value based on the first value, the second value corresponding to an amount of energy consumed by the test instrument; and

placing at least part of the test instrument in a high-impedance state when the second value exceeds a threshold;

wherein the test instrument comprises multiple channels; and

wherein the following are performed for a channel in the test instrument: determining the first value, determining the second value, and placing the test instrument in the high-impedance state.

2. The method of claim 1 , wherein determining the first value comprises obtaining a product of an input voltage value and a voltage corresponding to an input current value and, based on the product, producing an output voltage corresponding to the first value.

3. The method of claim 2 , wherein determining the second value comprises:

generating an output current based on the output voltage; and

integrating the output current over time to produce the second value.

4. The method of claim 3 , further comprising:

comparing the second value to the threshold; and

outputting a comparison value based on the comparison;

wherein the test instrument is placed in the high-impedance state by a latch in response to receipt of the comparison value, the latch outputting a control signal to place the test instrument in the high-impedance state.

5. The method of claim 4 , wherein the threshold is a first threshold; and

wherein the method further comprises:

following placement of the test instrument into the high-impedance state, lowering the power output by the test instrument so that the output current is less than a fixed current;

performing a reverse integration over time based on the fixed current to produce a third value;

comparing the third value to a second threshold; and

placing at least part of the test instrument in an operational state when, based on the comparing, the third value exceeds the second threshold.

6. The method of claim 5 , wherein comparing the third value to the second threshold results in a second comparison value; and

wherein the test instrument is returned to the normal operational state by a resetting of the latch in response to receipt of the second comparison value, the latch outputting a control signal to place the test instrument in the operational state.

7. The method of claim 2 , wherein the input voltage is based on a voltage across terminals of a power field-effect transistor; and

wherein the input current is based on voltage across terminals of a current sense resistor.

8. The method of claim 2 , wherein a multiplier circuit is used to determine the first value corresponding to an output voltage;

wherein the output voltage is output to a resistor to produce a current that exceeds a fixed current; and

wherein the second value is obtained by integrating the current over time.

9. The method of claim 1 , further comprising:

causing the test instrument to exit the high-impedance state following a decrease in the power output by the test instrument.

10. The method of claim 1 , further comprising:

following placing at least part of the test instrument in a high-impedance state, controlling the test instrument manually or programmatically to place the test instrument into an operational state.

11. Circuitry to control a test instrument, comprising:

a multiplier circuit to receive an input voltage and a voltage corresponding to an input current and to provide an output voltage representing power output of the test instrument;

an integrator circuit to output an integrated voltage based on a current corresponding to the output voltage, the integrated voltage representing energy consumed by the test instrument;

a comparator circuit to perform a comparison of the integrated voltage to a threshold, and to output a result signal based on the comparison; and

a latch to output a control signal to the test instrument based on the result signal, the control signal to place at least one of multiple channels of the test instrument in a high-impedance state.

12. The circuitry of claim 11 , further comprising:

a resistor to receive the output voltage, the current corresponding to the output voltage passing through the first resistor as a result of the output voltage received by the resistor.

13. The circuitry of claim 12 , wherein the resistor is a first resistor, the current corresponding to the output voltage is a first current, the integrated voltage is a first integrated voltage, the threshold is a first threshold, and the control signal is a first control signal; and

wherein the circuitry comprises:

a second resistor connected to a voltage source, a second current passing through the second resistor;

wherein, in a case that the second current is greater than the first current, the integrator circuit is configured to output a second integrated voltage based on the second current;

wherein the comparator circuit is configured to perform a comparison of the second integrated voltage to a second threshold, and to output a second result signal based on the comparison; and

wherein the latch is configured to output a second control signal to the test instrument based on the second result signal.

14. The circuitry of claim 13 , wherein the first control signal is to put the at least one of multiple channels of the test instrument into the high-impedance state, and the second control signal is to put the at least part of the test instrument into operational mode.

15. The circuitry of claim 11 , further comprising:

a power field-effect transistor across which a voltage corresponding to the input voltage is measured; and

a resistor through which a current corresponding to the input current is measured.

16. The circuitry of claim 11 , further comprising:

a power stage to output power from the instrument to a device under test, the power stage being configured to receive, and to respond to, the control signal.

17. The circuitry of claim 11 , wherein the integrator circuit comprises an operational amplifier.

18. Circuitry to control a test instrument, comprising:

an integrator circuit to output an integrated voltage based on a current corresponding primarily to an output power of the test instrument when the output power of the test instrument is above a threshold, the integrated voltage representing energy consumed by the test instrument;

a comparator circuit to perform a comparison of the integrated voltage to a threshold, and to output a result signal based on the comparison; and

a latch to output a control signal to the test instrument based on the result signal, the control signal to place at least one of multiple channels of the test instrument in a high-impedance state.