US 8,797,025 B2 · Compensation methods for digital source-measure-units (SMUs)

Abstract

A source-measure unit (SMU) may be implemented with respective digital control loops for output voltage and output current. The output voltage and output current may be measured with dedicated ADCs (analog-to-digital converters). The readings obtained by the ADCs may be compared to a setpoint, which may be set in a digital loop controller. The digital loop controller may be used to produce an output to drive a DAC (digital-to-analog converter) until the output voltage and/or output current and/or a function thereof reach the respective desired levels. The digital loop controller may implement respective integrating functions for the respective digital control loops, and may also implement a compensation function featuring pole-zero pairs to stabilize the respective current/voltage outputs. Coefficients of the compensation function may be calculated based on user programmable parameters corresponding to the gain bandwidth product, compensation frequency, and ratio of the added pole-zero frequencies.

Claims22

Dependent claims

A source-measure unit (SMU) comprising:

output terminals configured to couple the SMU to a device under test (DUT), and further configured to convey an analog output signal to the DUT to effect:
an output current flowing into the DUT;
and an output voltage in the DUT;
a first converter configured to generate a first digital value representative of the output current;
a second converter configured to generate a second digital value representative of the output voltage;
and a digital loop controller configured to receive the first digital value and the second digital value, and generate a digital control signal based on the first digital value and the second digital value to regulate a specified function of the output current and the output voltage to remain at a value corresponding to a setpoint, wherein the digital loop controller comprises:
an integrating function selectively associated with regulation of the output current and regulation of the output voltage;
and a compensating function configured to stabilize the analog output signal according to user programmable values corresponding to one or more compensation poles and zeros.

5 more elements

A method for providing an output current and an output voltage to a device under test (DUT) for testing the DUT, the method comprising:

regulating, via respective digital feedback loops for the output current and the output voltage, a specified function of the output current and the output voltage to remain at a desired value corresponding to a setpoint, said regulating comprising performing respective integrating functions within the respective digital feedback loops;
stabilizing the respective digital feedback loops through respective corresponding compensating functions, comprising providing respective specified input parameters to the respective corresponding compensating functions, wherein the respective specified input parameters comprise:
gain bandwidth corresponding to a gain of the respective integrating function;
compensation frequency corresponding to a geometric mean of a:
first frequency associated with a respective compensation pole;
and
a second frequency associated with a respective compensation zero;
and
a pole-zero frequency ratio corresponding to a ratio of the first frequency to the second frequency.

6 more elements

Dependencies are inferred from the claim text.

Compensation methods for digital source-measure-units (SMUs)

Life of this patent

Compensation methods for digital source-measure-units (SMUs)

Life of this patent

Abstract

Claims22