Current sense amplifier for voltage converter

1. A thermal calibration circuit for adjusting the gain of a variable gain amplifier, the thermal calibration circuit comprising:

an interface for receiving a signal that varies with temperature and for providing a signal related to the variation of the temperature;

a variable gain amplifier having an input and an output;

a switching circuit receiving an input for amplification by said variable gain amplifier and selectively decoupling said input and providing said signal related to the variation in temperature at said input to calibrate said variable gain amplifier;

a circuit at the output of said variable gain amplifier for developing a first current proportional to a difference between a current developed at the output of said variable gain amplifier and a reference current; and

said circuit at the output driving a further circuit to produce a gain control signal for adjusting the gain of the variable gain amplifier.

2. The thermal calibration circuit of claim 1 , wherein the interface receives a temperature dependent signal from a thermistor having a reference voltage applied across the thermistor generated across a precision resistor element and develops said signal related to the variation of the temperature comprising a current signal, said current signal developing a voltage signal across an input resistor selectively coupled to said input by said switching circuit.

3. The thermal calibration circuit of claim 2 , wherein the thermistor generates a signal related to the temperature of an output inductor of a voltage converter.

4. The thermal calibration circuit of claim 2 , wherein said variable gain amplifier has differential inputs and outputs, and wherein the differential outputs are coupled to a reference current source and a current mirror circuit for developing said first difference current; and further wherein said further circuit comprises a pair of transistors that generates said gain control signal by comparing said first difference current to a reference current developed by a fixed bias voltage.

5. The thermal calibration circuit of claim 4 , further wherein said further circuit includes a current limiting circuit for setting a limit on said gain control signal.

6. The thermal calibration circuit of claim 4 , wherein said variable gain amplifier includes a circuit for developing a gain control voltage from said gain control signal and a sample and hold circuit for selectively sampling said gain control voltage to set the gain of said variable gain amplifier.