Patent ID: 7557558

Claim:
A current reference for generating reference currents for use internal and external to an integrated circuit (IC), comprising: an IC having a plurality of input/output (I/O) pins; a voltage source within said IC which outputs a reference voltage V ref ; a current mirror which mirrors a current received at an input to at least one output; a transistor having its current circuit connected between said current mirror input and a first one of said I/O pins and which is driven by V ref ; a first resistor external to said IC and having a resistance R 1 , said first resistor coupled to said first I/O pin such that said first resistor conducts a current I ref which is proportional to V ref /R 1 , said current mirror providing currents which are proportional to I ref at respective ones of its outputs, one of said mirrored currents provided at a second one of said I/O pins for use external to said IC; circuitry external to said IC which requires a reference current, said external circuitry coupled to said second I/O pin, said circuitry comprising a negative voltage supply regulation circuit which regulates a negative supply voltage channel; wherein said negative supply voltage channel is accessible external to said IC, further comprising: a negative supply voltage generation circuit which provides said negative supply voltage to be regulated, said negative supply voltage generation circuit arranged to vary said negative supply voltage in response to a control signal; wherein said negative voltage supply regulation circuit comprises: a second resistor external to said IC and connected between said second I/O pin and said negative supply voltage channel such that said second resistor conducts a current which is proportional to Iref; and an error amplifier having first and second inputs and an output, said output providing said control signal to said negative supply voltage generation circuit, said first input coupled to said second I/O pin and said second input coupled to a second reference voltage, said error amplifier arranged to provide said control signal so as to drive the difference between the voltages at said first and second inputs toward zero.