Maxim Integrated Products, Inc.

Bruce Michael Furman

Charles M Allen

The present invention overcomes ISI by precompensating for the anticipated high-frequency energy losses in the transmission media. This precompensation is accomplished using a preemphasis waveform, i.e., driving the differential signal to a value larger than normal on a signal edge. Preemphasis increases the slew rate of edges inside data with a lot of transitions relative to data with fewer transitions, thereby compensating for the low-pass effects of the transmission cable. The present invention further contemplates adaptive control for ensuring that varying operating conditions do not effect preemphasis waveform generation. The first approach involves tracking the operation of a replicate driver for each main driver and adaptively controlling each main driver depending upon feedback from the replicate driver. A second approach, that is both more complicated and more effective, involves measuring the signal and the line impedance at the output of the main driver and adaptively controlling the main driver in response.

Methods and circuits for generating a preemphasis waveform

A balanced input circuit which is used with an operational amplifier to obtain the difference between two input signals. In a temperature sensor application, one input signal is proportional to absolute temperature (PTAT) and one signal is complimentary to absolute temperature (CTAT) with the CTAT signal being the base-emitter voltage (V ) of a bipolar transistor. In this application the operational amplifier output is the PTAT signal minus V times a scale factor determined by the feedback loop of the operational amplifier.

Balanced input for temperature sensor

Curvature in the temperature response of junction voltage of a diode or transistor is compensated by circuitry which offsets the curvature at temperatures below a reference temperature and at temperatures above a reference temperature. Two current sources are provided including a first current source of current proportional to absolute temperature (PTAT) less a current complimentary to absolute temperature (CTAT) and a second current source of PTAT plus beta times CTAT (PTAT&plus;&bgr;CTAT). A first current path is connected between a first current path between two potential levels (V,G,) including the first current source serially connected with first and second semiconductor junctions, a second current path between the two potential levels including the second current source serially connected with a first three terminal transistor including a control terminal, means coupling the voltage across the first and second semiconductor junction devices to the control terminal of the first transistor, a second three terminal transistor including a control terminal, and means coupling a voltage from the first transistor to the control terminal of the second transistor to control current through the second transistor.

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Palo Alto, CA, United States of America

Bruce Michael Furman