A Multi-phase Series-Parallel with Bond Wire Auxiliary Fully-Integrated 250pF Switched-Capacitor with 13.6mV output ripple for Supplying Temperature Sensor with 0.1°C Accuracy to Early Detect COVID-19

Temperature sensing is an important means for the early detection of COVID-19 infection. Thus, it is important to supply a $0.95V(\pm 0.5\%)$ to the wearable temperature sensor (top left in Fig. 1) by a fully integrated switched-capacitor (SC) converter with small on-chip capacitors C
FLY
and C
OUT
. For small chip area, the value of C
TOT
(=C
FLY
+C
OUT
, where C
FLY
and C
OUT
are flying capacitor and output capacitor, respectively) needs to be less than 250pF to ensure the temperature sensor is small enough. The required temperature detection accuracy of 0.1°C limits the output voltage ripple ΔV
OUT
of the SC to less than 15mV, where ΔV
OUT
is inversely proportional to the switching frequency F
CLK
and C
OUT
. If C
TOT
<250pF and ΔV
OUT<
15mV, then F
CLK
is tens of GHz. In [1], a digital 2-/3-Phase SC is used to decrease ΔV
OUT
and to improve efficiency, but the required off-chip capacitor is not suitable for wearable devices. In [2], an SC Resistance low-dropout (SCR-DLDO) regulator uses a small on-chip capacitor of 0.365nF, but F
CLK
of 1.55GHz causes a larger switching loss. In [3], since F
CLK
is determined by (LC)
^1/2
=47.5MHz, the large on-chip inductor will cause higher conduction power loss due to its worse quality factor. Moreover, a pulse skipping technique is required to decrease F
CLK
and enhance light-load efficiency at the cost of large ΔV
OUT
. Although [4] attempts to have many voltage conversion ratios (VCR) to maintain high efficiency, there are still problems with reduced drive capability and reduced efficiency on some VCRs. In [5], switching frequency can be reduced to 95 MHz, using a capacitor-dithering method with 41 interleaved phases. However, the peak efficiency degrades to 70.8% due to the charge sharing loss from the 41 interleaving cells.