A PNP-Based Temperature Sensor With Continuous-Time Readout and $\pm$ 0.1 $^{\circ}$ C (3 $\sigma$ ) Inaccuracy From $-$ 55 $^{\circ}$ C to 125 $^{\circ}$ C

This article describes a PNP-based temperature sensor that achieves both high energy efficiency and accuracy. Two resistors convert the CTAT and PTAT voltages generated by a PNP-based front-end into two currents whose ratio is then digitized by a continuous-time (CT)
$\Delta \Sigma $
-modulator. Chopping and dynamic-element-matching (DEM) are used to mitigate the effects of component mismatch and 1/
$f$
noise, while the spread in
$V_{\mathbf{BE}}$
and in the ratio of the two resistors is digitally trimmed at room temperature (RT). Fabricated in a 0.18
$\mu$
m CMOS process, the sensor occupies 0.12 mm
$^{2}$
, and draws 9.5
$\mu $
A from a supply voltage ranging from 1.7 to 2.2 V. Measurements on 40 samples from one batch show that it achieves an inaccuracy of
$\pm$
0.1
$^{\circ}$
C (3
$\sigma$
) from
$-$
55
$^{\circ}$
C to 125
$^{\circ}$
C, and a commensurate supply sensitivity of only 0.01
$^{\circ}$
C/V. Furthermore, it achieves high energy efficiency, with a resolution Figure of Merit (FoM) of 0.85 pJ
$\cdot$
K
$^{2}$
.