Various embodiments of a voltage level detector implemented as an integrated circuit whose trip point is approximately constant over variations in temperature as well as variations in transistor fabrication parameters are disclosed along with a differential amplifier whose input offset voltage is highly immune to said variations. In one embodiment, a voltage generator supplies a composite voltage to the gate of the tail current transistor of the voltage level detector or differential amplifier. The first component of the voltage is approximately equal to the threshold voltage of NMOS transistors comprised in the device over variations in operating temperature as well as variations in transistor fabrication parameters while the second component is approximately constant with respect to said variations. When applied to the gate of the tail current transistor, the first component may turn the transistor on in spite of the above-mentioned parametric variations.
A thermostat circuit is arranged for dual purpose operation to save pins in a small package. The circuit includes a temperature sensor circuit, a trip-point reference circuit, a switching circuit, an amplifier circuit, and a comparator circuit. The trip-point reference circuit provides a reference voltage that corresponds to a desired trip-point level. The temperature sensor circuit provides a sense voltage that corresponds to temperature. During a normal operating mode the sense voltage is coupled to the input of the amplifier circuit via the switching circuit, while during a test mode the reference voltage is coupled to an input of the amplifier circuit. The amplifier circuit buffers a voltage to one output pin. The comparator circuit compares the reference voltage to the sense voltage to provide a trip-point detection voltage for another output pin. An input pin is provided for selection of either a test mode or a non-test mode.
A converter comprising a comparator having a first input operable to receive a first signal, a second input operable to receive a second signal, and an output, a switch for sinking a portion of the first signal, wherein the switch is responsive to the output, and an integrator connected to the first input, wherein the first signal is a voltage developed by the integrator when a current proportional to the absolute temperature is applied thereto. A method for measuring temperature of a device using a comparator and converting the bitstream of the comparator to a digital output is also given. Because of the rules governing abstracts, this abstract should not be used to construe the claims.
A bandgap reference circuit inputs a reference potential trimming signal therein, generates a reference potential using PN-junction diode characteristics and generates a first temperature-dependent potential dependent on the temperature. A subtraction amplifier circuit inputs the reference potential, the first temperature-dependent potential and a subtracter trimming signal therein and generates a second temperature-dependent potential amplified by subtraction amplification of both a constant bias potential obtained by performing multiplication on the reference potential and the first temperature-dependent potential. An A/D converter inputs the reference potential and the second temperature-dependent potential therein and A/D-converts the second temperature-dependent potential by reference to the reference potential to thereby output temperature decision results.
The present invention provides a method and apparatus for compensating for temperature effects in the operation of semiconductor processes circuitry, such as reference circuits. The method operates on the realization that the second order effects such as "curvature" in the reference voltage variation over a temperature range is removed. The reference voltage variation over a temperature range can be represented as a straight line. This method provides for the trimming of the absolute voltage by scaling the reference voltage at a first temperature to the desired value by a temperature independent voltage. Then, at a second temperature, the output voltage slope is corrected by adding or subtracting a voltage which is always zero at the first temperature.
