A 5µW fractional CMOS bandgap voltage and current reference

Design of a sub-1V, low power, fractional bandgap voltage reference (V_r ~ 0.6V) conjoined with a current reference (I_r ~ 1μA) in standard 90 nm digital CMOS is proposed, utilizing standard parasitic substrate PNPs. A positive temperature coefficient (TC) voltage is generated across a feed-back resistor, R_f, via a negative TC emitter-base voltage (V_EB) on one side of R_f and the looped-back V_r output on the other side, which has a near zero TC. The resulting current, I_x = (V_r - V_EB) /R_f, has a zero current crossing point that can be set roughly around the mid-point of minimum and maximum operating temperatures. As such, I_x supplies the needed positive TC current to the bandgap´s proportional to absolute temperature (PTAT) current loop that facilitates generating the residual zero TC current, I_r, which is concurrently fed to R_o to produce V_r. Simulations show V_r of about 0.6V at TC of about ±10ppm/°C (with trim) can be achieved over span of -50°C <; T <; 150°C. Accordingly, simulating for bandgap´s operation for +0.9V > V_DD > +5V, indicates that I_DD of about 5μA, and voltage coefficient (VC) of about ±50 ppm/V are achievable.