Rail-to-Rail, Linear Hot-Electron Injection Programming of Floating-Gate V oltage Bias Generators at 13-Bit Resolution Chenling Huang

Abstract

Hot-electron injection is widely used for accurate pro- gramming of on-chip floating-gate voltage and current reference s. The conventional programming approach involves adapting the duration and magnitude of the injec t i o np u l s e sb a s e do nap r e d i c - tive model which is estimated by using measured data. However, varying the pulse-widths or amplitu des introduces nonlinearity in the injection process which complic ates the modeling, calibration and programming procedure. In this paper, we propose a linea r hot-electron injection technique which signi ficantly simpli fies the programming procedure, and can achieve programming accuracy greater than 13-b which is limited by the thermal noise from the in- jection process. The procedure emp loys an active feedback circuit which ensures that all the nonlinear factors affecting the hot-elec- tron injection process are held constant, thus ac hieving a stable and controllable injection rate. Measured results using an array of floating-gate voltage reference prototyped in a 0.5- ms t a n d a r d CMOS process demonstrate that the injecti on rates can be con- trolled from 0.1 to 4.1 V for the programmable voltage range. Using 50-ms injection pulses, we show that the average injection rate can be adapted from 6.9 to 250 V .