EXTERNAL COMPONENT-LESS PVT COMPENSATION SCHEME FOR IO BUFFERS

摘要

Disclosed is a system and method for providing Process-Voltage-Temperature (PVT) compensation for an Input/Output interface. An embodiment may connect an analog section and a digital section together to generate and measure an oscillation frequency (FOSC) used to look up a corresponding PVT control bit value in a look-up table. The analog section may be comprised of a voltage reduction system that reduces a bandgap reference voltage (VBGR) to half the supplied VBGR to a current mirror that supplies a PVT current (IPVT) to driver bit cells and a proportional mirrored control current (ICNTL) to a current controlled oscillator (CCO), which generates FOSC. The digital section may be used in combination with a frequency variable resistor and beta multiplier connected to the CCO to calibrate the capacitance of the CCO to tune out the process variation of the CCO capacitance and render FOSC to be linearly dependent on ICNTL.

主权项

1. A method to provide Process-Voltage-Temperature (PVT) compensation for an Input/Output (IO) interface, said IO interface having a bandgap reference voltage (VBGR) and a reference frequency (FREF), said method comprising:
connecting said VBGR to a voltage reduction system; reducing said VBGR by substantially half at said voltage reduction system to produce VBGR/2; connecting said VBGR/2 to a current mirror system; connecting said current mirror system to a high supply voltage (VDD); connecting a driver bit cell to a low supply voltage (VSS); connecting said current mirror system to said driver bit cell such that a process-variable-temperature current (IPVT) flows through said driver bit cell; connecting said current mirror system to a compensated current controlled oscillator; mirroring said IPVT at said current mirror system such that said compensated current controlled oscillator receives a control current (ICNTL) that is proportional to said IPVT; generating an oscillation frequency (FOSC) at said compensated current controlled oscillator that is a function of said ICNTL; connecting said FOSC to a digital system; connecting said FREF to said digital system; measuring, by said digital system, a desired count period based on FREF; accumulating, by said digital system, a count of said FOSC at said digital system during said desired count period; looking up, by said digital system, a PVT control bit value that correlates to said accumulated count of said FOSC in a look-up table containing a predetermined correlation of potential count values of said FOSC to desired PVT control bit values; and providing, by said digital system, said looked up PVT control bit value to said IO interface.