US 5,852,379 AGranted

Fuse tunable, RC-generated pulse generator

AssigneeIntegrated Silicon Solution, Inc.

InventorYong H. Jiang

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Abstract

A tunable phase generator is disclosed suitable for use in integrated circuits. The phase generator includes a delay element wherein passive resistors and conductors are employed to provide relatively constant delays despite changes in operating temperatures and voltages. The phase generator is driven by a clock signal and generates therefrom a self-resettable output signal pulse with a selectable pulse width no longer than the width of the clock signal. The variable widths are provided by varying the delays of the delay elements and adding combinational logic between respective delay elements and at the input and output of the phase generator that ensure that, in most situations, the output signal pulse is reset after a delay that is independent of the pulse width of the clock signal. Delays are lengthened by decreasing the current available to a delay element for charging the capacitors. Delays are decreased by disconnecting at least some of the capacitors so that the corresponding delay element has virtually no delay.

Claims18

Dependent claims

A tunable pulse generator, comprising:

an input port for receiving a stimulus signal;
a chain of delay elements;
and
a logic circuit coupled to the input port and an output of the chain of delay elements for generating a pulse in response to a predefined logic transition in the stimulus signal, where the length of the generated pulse is governed by a delay time associated with the chain of delay elements, and wherein the pulse automatically terminates after a tunable pulse duration;
at least one of the delay elements including;
a tunable inverter structure including a plurality of inverters with common inputs coupled to a first signal;
one subset of the plurality of inverters having an output coupled to a first output node via a respective fuse;
another subset having an output coupled directly to the first output node;
wherein the respective fuse has a respective open/closed circuit status and an output of the tunable inverter structure is a second signal having a current strength that is a function of the open/closed circuit status of the respective fuses;
and
a delay structure including a passive resistor with an input coupled to receive the second signal and an associated resistance that varies insignificantly as a function of operating temperature and operating voltage, and a load circuit with an input coupled to an output of the passive resistor and an associated capacitance determined by gate capacitances of transistors composing the load circuit, the transistors being connected so that the associated capacitance varies insignificantly as a function of operating temperature and operating voltage;
wherein the resistance and capacitance determine in accordance with current strength of the second signal a delay associated with the delay structure that determines voltage profile characteristics of a delay output signal generated by the delay structure in response to transitions of the second signal.

9 more elements

A tunable pulse generator implemented as part of an integrated circuit, comprising:

an input circuit configured via a one time programming mechanism to generate a pulsed input signal with tuned current strength;
an RC delay structure driven by the pulsed input signal, the delay structure being configured to provide a delay output signal whose voltage profile is determined by the RC constant of the delay structure and the tuned current strength of the pulsed input signal, the RC constant varying insignificantly as a function of temperature and voltage;
a logic gate structure with an input configured to receive the delay output signal;
such that the logic gate structure generates a gated output signal that makes a state transition only when the voltage level of the delay output signal exceeds the threshold voltage of the logic gate structure, resulting in a signal delay being introduced between an active transition of the pulsed input signal and a corresponding change in the gated output signal, the length of the signal delay being determined by:
the RC constant of the delay structure, and
the tuned current strength of the pulsed input signal;
wherein the input circuit comprises a tunable inverter structure including a plurality of inverters with common inputs coupled to a first signal;
one subset of the plurality of inverters having an output coupled to a first output node via a respective fuse;
another subset having an output coupled directly to the first output node;
wherein the respective fuse has a respective open/closed circuit status and an output of the tunable inverter structure is a second signal having a current strength that is a function of the open/closed circuit status of the respective fuses, the second signal being the same as the pulsed input signal;
and
wherein the delay structure comprises a passive resistor and a load circuit whose respective resistance and capacitance determine the RC constant and vary insignificantly as a function of temperature and voltage.

9 more elements

Dependencies are inferred from the claim text.