IC Implementation of Subthreshold Current Temperature Independent Power-on-Reset Circuit

Abstract: Power-on-reset (POR) circuit with low current consumption, temperature independent has been developed. The circuit contains several sub-circuits such as self-biased current generator, analog comparator with hysteresis, Schmitt trigger and supply filter. Two nano amp currents with positive temperature coefficients (PTAT), generated from self-bias current generator - one applied on resistor, and one applied on two diode string connected to the supply, are compared at the two inputs of analog comparator. By controlling the resistance value and the multiplier of the current bias, the low-to-high threshold is precisely settled. This also allows to control the temperature behavior of the voltage on the inputs of the comparator and make POR threshold levels less temperature dependent. A hysteresis has been added in the analog comparator, which is used to set the high-to-low POR threshold and to prevent the circuitfrom wrong triggering and oscillations. This circuit is designed in TSMC 0.18 $\mu$m technology kit. The simulations are performed at schematic level only, with 5V supply voltage.