Texas Instruments Corporation

Siliconsystems, Inc.

Geert Deveirman

Simon Edward Willard

Michael J McNutt

Rajagopal Sundararaman

Jay Standiford

An on-chip fuse circuit. The circuit includes a fuse capable of being blown during a programming operation, as well as output logic for determining whether the fuse is blown. A protection circuit is provided for protecting the output logic during programming. An evaluation circuit is provided, for evaluating whether the fuse is blown. The evaluation circuit includes a first current source coupled to the fuse, providing a first predetermined current so as to activate the output logic to read out the condition of the fuse during normal operation, as well as a second current source coupled to the fuse, providing a second predetermined current, substantially less than the first predetermined current, so as to activate the output logic to read out the condition of the fuse during an evaluation mode such that a blown condition is indicated by the output logic only if the resistance of the fuse is substantially greater than that required for the output logic to indicate a blown condition during normal operation. According to another aspect of the invention there is provided an on-chip fuse circuit including a first fuse and a second fuse, both being capable of being blown during a programming operation. Output logic is provided for determining whether the fuse is blown, the output logic including first indication logic for indicating whether both of the fuses are blown, during an evaluation mode, and second indication logic for indicating a blown state of the fuse circuit if either of the fuses is blown. A protection circuit is provided for protecting the output logic during programming. An evaluation circuit is provided for evaluating whether the fuse is blown.

Fuse cell for on-chip trimming

A high-frequency integrated continuous-time filter with built-in test mode. The present invention provides the ability to easily track the cutoff frequency of the filter without the additional power and area requirements and noise sources present in prior art master/slave tuning schemes. Furthermore, the filter being tested is the actual filter that is used to process signals, unlike the prior art where a similar but separate filter or oscillator is used to tune the bias values for both circuits. Better tuning accuracy is thus obtained in the present invention. The circuit is designed to oscillate in test mode at the cutoff frequency of the filter. Oscillation is achieved by moving the poles of the filter from the left half-plane either onto the imaginary axis or into the right half-plane. The filter frequency accuracy is established by trimming the frequency of the oscillation in test mode during wafer probe or by adjusting the circuit biasing to tune the cutoff frequency in test mode during power-up or between reads in a memory system. The oscillation is disabled during normal operation of the filter.

Tuning method for integrated continuous-time filters

A filter circuit with improved performance characteristics. A biquadratic transconductance-C filter includes a differentiator in the feed forward path of the input signal to compensate for the non-ideal operation of the transconductance elements and to simplify the performance requirements of a variable gain amplifier also in the feed forward path. The variable gain amplifier and feed forward technique are used to create two programmable magnitude, opposite sign zeros on the real axis, whose effect on the incoming data signal results in variable pulse slimming. The addition of a differentiator in the feed forward path eliminates the effect of the output admittance of the transconductance elements on the filter's group delay. The differentiator acts as a first order, high pass filter. The frequency of the differentiator is controlled so that the input signal is attenuated before it is provided to the variable gain amplifier. This reduces the dynamic range requirements of the variable gain amplifier without affecting group delay requirements.

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Irvine, CA, United States of America

Geert Deveirman