Analog Devices,inc.

John Blake

David Thomson

John Anthony Cleary

Evaldo M Miranda, Jr

Michael G Tuthill

Patrick J Meehan

Evaldo M Miranda

David Hanrahan

Michelle Mahony

Paul Shepherd

Lorcan Mac Manus

Kohji Yoshida

The present invention is connected across a sense resistor which carries a current of interest. A first pair of cross-coupled switches are connected between the sense resistor and respective input capacitors, and a second pair of cross-coupled switches are connected between the input capacitors and the inputs of an amplifier having differential inputs and outputs. Feedback capacitors are connected between each of the amplifier's outputs and inputs. A control circuit operates the cross-coupled switches in accordance with a switching cycle, during which the connections between the sense resistor and the input capacitors are interchanged, after which the connections between the input capacitors and the differential amplifier are interchanged. When so arranged, the sensed voltage is sampled on the input capacitors and transferred to the feedback capacitors to produce a differential output voltage V from the differential amplifier which is proportional to the current of interest.

Current measurement circuit

A four current transistor temperature sensor comprises a p-n junction, preferably the base-emitter junction of a bipolar transistor, which is driven with four different currents in a predetermined sequence. Each of the four currents induces a respective base-emitter voltage, which is measured. The temperature of the transistor is calculated based on the values of the four driving currents and the four measured base-emitter voltages. The four driving currents (I , I , I and I ) are preferably arranged such that I *I , I *I , I /I &equals;A and I /I &equals;A, where A is a predetermined current ratio. I and I produce respective base-emitter voltages which are subtracted from each other to produce &Dgr;V , and I and I produce respective base-emitter voltages which are subtracted from each other to produce &Dgr;V . When so arranged, the difference between &Dgr;V and &Dgr;V is entirely due to the effect of series base and emitter resistances r and r . Therefore, the &Dgr;V &minus;&Dgr;V value provides a correction factor which enables temperature measurement errors due to r and r to be eliminated.

Four current transistor temperature sensor and method

An operating circuit ( ) for controlling the speed of a cooling fan motor ( ) for computer cabinetry ( ), and for determining an under-speed condition in the fan motor ( ) comprises a control circuit ( ) which controls a variable output signal generator circuit ( ) for outputting a pulse width modulated signal corresponding to the desired fan speed for switching a switching circuit ( ) in a power supply circuit of the fan motor ( ) for pulse width modulating the power supply to the fan motor ( ). A monitoring resistor (R ), a capacitor (C ) and a circuit ( ) provides a tachometer signal to the operating circuit ( ). A gate circuit ( ) gates the second and fourth pulses of the tachometer signal to a counter ( ) which counts clock pulses from a clock signal generating circuit ( ) between the rising edges of the second and fourth pulses which are in turn stored in a register ( ) for comparison with a reference count by a comparator ( ). The comparator ( ) outputs an alert signal in the event of the count in the register ( ) exceeding the reference count indicating under-speed of the fan. The control circuit ( ) controls the signal generator circuit ( ) for holding the pulse width modulated signal outputted to the switching circuit ( ) on during a duty cycle between the rising edges of the second and fourth pulses of the tachometer signal so that the tachometer signal remains available until the fan speed has been determined.

Method and apparatus for determining fan speed

A fan speed control system for an electronic equipment enclosure comprises means for determining temperature at a plurality of locations within the enclosure, means for determining operating parameters for the fan control system, means for setting operating speed of at least one cooling fan, and means for exchanging information signals relating to fan speed control system operation with an external controller. A method is also provided for controlling fan speed for an electronic equipment enclosure comprising the steps of determining temperature at a plurality of locations within the enclosure, determining operating parameters for the fan control system, setting operating speed of at least one cooling fan, and exchanging information signals relating to fan speed control system operation with an external controller.

Fan speed control system

An IC monitoring chip (,) for remotely monitoring the output of a thermal diode (,) formed in the substrate of a CPU (,) for monitoring the temperature of a thermal plate (,) of the CPU (,) comprises a signal conditioning circuit (,) which relays the output from the diode (,) to an analog-to-digital converter (,), which in turns outputs a two's compliment signal to an adder (,). The adder (,) adds the two's compliment signal to a temperature offset value stored in a temperature offset register (,), which compensates for the temperature difference between the diode (,) and the thermal plate (,). Comparators (,) and (,) compare the output from the adder (,) with upper and lower predetermined temperature limits in upper and lower limit registers (,) and (,) for determining the temperature of the thermal plate (,). The temperature offset value is stored in ROM (,) of the computer (,) and is written to the register (,) each time the computer (,) is powered up. The IC chip (,) operates independently of the CPU (,).

IC monitoring chip and a method for monitoring temperature of a component in a computer

A decoupled switched current temperature circuit with compounded .DELTA.V.sub.be includes an amplifier having an inverting input with corresponding non-inverting output and a non-inverting input with a corresponding inverting output; a PN junction connected to the non-inverting input through a first input capacitor and a voltage reference circuit is connected to the inverting input through a second input capacitor; a current supply includes a low current source and a high current source; a switching device applies the high current source to the PN junction and applies the low current source to the PN junction for providing the .DELTA.V.sub.be of the PN junction to the first capacitor; a first feedback capacitor is interconnected between the inverting output and the non-inverting input and a second feedback capacitor is interconnected between the non-inverting output and inverting input of the amplifier to define the gain on each of the inputs to produce a differential voltage across the outputs representative of the temperature of the PN junction; first and second reset switching devices discharge the first and second feedback capacitors, respectively, and a multi-phase switched device alternately interchanges the connection of the first and second input capacitors with the amplifier inputs for compounding the single .DELTA.V.sub.be .

Decoupled switched current temperature circuit with compounded .DELTA.V

A digital signal processor for a PRML system includes: an NMOS pass transistors gain control circuit responsive to a digital data signal for adjusting the gain of the digital data signal; an NMOS pass transistor phase control circuit responsive to the digital data signal for adjusting the phase of the data signal; and an NMOS pass transistor Viterbi maximum likelihood detector circuit for determining the most probable sequence of symbols in the data signal.

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Limerick, Ireland

John Blake