Circuit and Method for Trimming Integrated Circuits

Abstract

A programmable after-package, on-chip reference voltage trim circuit for an integrated circuit having a plurality of programmable trim cells generating a programmed sequence. A converter is provided to convert the bit sequence into a trim current. The trim current is added to an initial value of a reference voltage to be trimmed, as generated by the integrated circuit. Once the correct value of the trim current is determined, isolation circuitry is programmed to isolate the trim circuitry from the remainder of the IC, thereby freeing the logic and package pins associated with the IC for use by users of the IC. The preferred trim circuitry includes fuses which are blown in accordance with a bit value supplied to the trim cell to permanently fix a trim current value, once a best fit value is determined.

1 . An integrated circuit having a post-trim functionality, comprising:
 a pin used for an after-package trimming function involving adjustment of an element of the integrated circuit;   wherein after the trimming function is complete, the pin is used during execution of the post-trim functionality.   
   
   
       2 . The integrated circuit of  claim 1 , further comprising:
 trim circuitry responsive to a signal on the pin, and for determining an initial value of an output of the integrated circuit, and for determining a value by which the initial value must be adjusted.   
   
   
       3 . The integrated circuit of  claim 2  wherein the trim circuitry determines a value by which the initial value must be adjusted by comparing that initial value with a known reference to determine an offset from a target value. 
   
   
       4 . The integrated circuit of  claim 3  wherein the trim circuitry is further configured for generating a trim value based on the initial value and the offset. 
   
   
       5 . The integrated circuit of  claim 4  wherein the trim circuitry is further configured for permanently fixing the trim value in the integrated circuit. 
   
   
       6 . The integrated circuit of  claim 5  wherein permanently fixing the trim value in the integrated circuit includes isolating at least a portion of the trim circuitry from remainder of circuitry included in the integrated circuit. 
   
   
       7 . The integrated circuit of  claim 5  wherein permanently fixing the trim value in the integrated circuit includes intentionally blowing one or more fuses. 
   
   
       8 . The integrated circuit of  claim 4  wherein the trim circuitry is further configured for adjusting the element in accordance with the trim value. 
   
   
       9 . The integrated circuit of  claim 2  wherein the trim circuitry is further configured for, after the trimming function is complete, isolating at least a portion of the trim circuitry from remainder of circuitry included in the integrated circuit. 
   
   
       10 . The integrated circuit of  claim 9  wherein isolating at least a portion of the trim circuitry includes intentionally blowing one or more fuses. 
   
   
       11 . The integrated circuit of  claim 9  wherein isolating at least a portion of the trim circuitry includes isolating the trim circuitry from the pin. 
   
   
       12 . The integrated circuit of  claim 11  wherein isolating at least a portion of the trim circuitry further includes isolating the trim circuitry from a memory device of the integrated circuit. 
   
   
       13 . The integrated circuit of  claim 12  wherein the memory device is a register. 
   
   
       14 . A method for after-package trimming an element included in an integrated circuit having a post-trim functionality, the method comprising:
 using circuitry, including at least some circuitry of the integrated circuit, to perform a trimming function comprising:
 determining an initial value of an output of the integrated circuit; and 
 determining a value by which the initial value must be adjusted; 
   after the trimming function is complete, isolating the at least some circuitry of the integrated circuit, so that the at least some circuitry can be used during execution of the post-trim functionality.   
   
   
       15 . The method of  claim 14  wherein determining a value by which the initial value must be adjusted comprises:
 comparing that initial value with a known reference to determine an offset from a target value; and   generating a trim value based on the initial value and the offset.   
   
   
       16 . The method of  claim 15  wherein the trimming function further comprises adjusting the element in accordance with the trim value. 
   
   
       17 . The method of  claim 14  wherein isolating the at least some circuitry of the integrated circuit includes intentionally blowing one or more fuses. 
   
   
       18 . A system for after-package trimming an element included in an integrated circuit having a post-trim functionality, the system comprising:
 circuitry, including at least some circuitry of the integrated circuit, for performing a trimming function comprising:
 circuitry for determining an initial value of an output of the integrated circuit; and 
 circuitry for determining a value by which the initial value must be adjusted; 
   circuitry for isolating the at least some circuitry of the integrated circuit, after the trimming function is complete, so that the at least some circuitry can be used during execution of the post-trim functionality.   
   
   
       19 . The system of  claim 18  wherein the circuitry for determining a value by which the initial value must be adjusted comprises:
 circuitry for comparing that initial value with a known reference to determine an offset from a target value; and   circuitry for generating a trim value based on the initial value and the offset.   
   
   
       20 . The system of  claim 19  further comprising circuitry for adjusting the element in accordance with the trim value.