EMI rejection for temperature sensing diodes

A method comprising:

• establishing respective identical impedances at an input terminal of a semiconductor device and an output terminal of the semiconductor device;
• generating a constant voltage component at a control terminal configured to couple to the input terminal of the semiconductor device;
• the semiconductor device conducting a first device-current in response to said generating the constant voltage component;
• maintaining a first control voltage at the control terminal, wherein the first control voltage is equivalent to a sum of the constant voltage component plus a first device-voltage developed across the input terminal and the output terminal of the semiconductor device in response to the first device-current;
• wherein in accordance with said maintaining the first control voltage, the first device-current is determined by the constant voltage component and respective ohmic components of the identical impedances.

A temperature measurement system comprising:

• a semiconductor device having an input terminal, an output terminal, and a specified, non-linear input-output characteristic that varies with temperature;
• a control circuit having a first terminal, a second terminal, and a control terminal, wherein the first terminal is configured to couple to the input terminal of the semiconductor device and the second terminal is configured to couple to the output terminal of the semiconductor device;
• a first resistance configured to couple to the control terminal;
• a second resistance having a specified value and configured to couple between the first terminal and the control terminal;
• a third resistance having the specified value and configured to couple between the second terminal and ground;
• and
• a current source configured to alternately provide to the first resistance:
• a first current for developing a corresponding first constant voltage component at the control terminal and a corresponding first device-current in the semiconductor device;
• and
• a second current for developing a corresponding second constant voltage component at the control terminal, and a corresponding second device-current in the semiconductor device;
• wherein the first constant voltage component is equivalent to a product of the first current and the first resistance, and the second constant voltage component is equivalent to a product of the second current and the first resistance;
• a converter circuit operable to sample a first device-voltage developed across the input terminal and the output terminal of the semiconductor device in response to the first device-current and a second device-voltage developed across the input terminal and the output terminal of the semiconductor device in response to the second device-current, and to generate a numeric value according to a difference between the first device-voltage and the second device-voltage, wherein the numeric value corresponds to a temperature of the semiconductor device;
• wherein the control circuit is operable to alternately maintain a first control voltage and a second control voltage at the control terminal, wherein the first control voltage is equivalent to a sum of the first constant voltage component plus the first device-voltage, and the second control voltage is equivalent to a sum of the second constant voltage component plus the second device-voltage;
• and
• wherein in accordance with the maintained first control voltage, the first device-current is determined by the first constant voltage component, the second resistance, and the third resistance, and in accordance with the maintained second control voltage, the second device-current is determined by the second constant voltage component, the second resistance, and the third resistance.

A temperature measurement system comprising:

• a semiconductor device having an input terminal, an output terminal, and a specified, non-linear input-output characteristic that varies with temperature;
• a first resistor network having two end terminals, and configured to have a settable resistance, and further configured to have one of its two end terminals coupled to the input terminal of the semiconductor device;
• a second resistor network having two end terminals, and configured to have a settable resistance, and further configured to have one of its two end terminals couple to the output of the semiconductor device and the other of its two end terminals couple to ground;
• a control circuit having a first terminal, a second terminal, and a control terminal, wherein the first terminal is configured to couple to the input terminal of the semiconductor device, the second terminal is configured to couple to the output terminal of the semiconductor device, and the control terminal is configured to couple to the other of the two end terminals of the first resistor network, wherein the control circuit is operable to:
• alternately set to a first resistance and a second resistance both the first resistor network and the second resistor network simultaneously;
• when the first resistor network and the second resistor network are set to the first resistance, generate and maintain an constant voltage component at the control terminal to develop a first device-current in the semiconductor device, and maintain a first control voltage at the control terminal, wherein the first control voltage is equivalent to a sum of the constant voltage component plus a first device-voltage developed across the input terminal and the output terminal of the semiconductor device in response to the first device-current;
• when the first resistor network and the second resistor network are set to the second resistance, generate and maintain the constant voltage component at the control terminal to develop a second device-current in the semiconductor device, and maintain a second control voltage at the control terminal, wherein the second control voltage is equivalent to a sum of the constant voltage component plus a second device-voltage developed across the input terminal and the output terminal of the semiconductor device in response to the second device-current;
• and
• a converter circuit operable to sample the first device-voltage and the second device-voltage, and produce a numeric value according to a difference between the first device-voltage and the second device-voltage, wherein the numeric value corresponds to a temperature of the semiconductor device;
• wherein in accordance with the maintained first control voltage, the first device-current is determined by the constant voltage component, the second resistance, and the third resistance, and in accordance with the maintained second control voltage, the second device-current is determined by the constant voltage component, the second resistance, and the third resistance.