Fully-integrated dickson converters for single photon avalanche diode arrays

Abstract

This article presents a novel low EMI technique to regulate the output voltage of fully-integrated switched capacitor Dickson type step-up DC/DC converters for SPAD arrays implemented in the Silterra 0.13 μm HV-CMOS process. SPAD sensors are extremely sensitive to EMI and therefore require careful biasing. This design utilises current sources to limit the current flow into the flying capacitors altering the converter ratio and reduces the discontinuous pulse currents associated with capacitive converters. A variable voltage-controlled reference current enables output voltage regulation. The proposed four stage converter boosts 3.3 V up to an adjustable 15 V output voltage. A typical Dickson converter regulated by frequency control and the proposed current controlled converter were designed and manufactured to compare performance. Measurements confirm that the proposed design reduces the output ripple by more than 2 V when compared to the typical converter. The inclusion of the proposed voltage regulation technique reduces EMI which enables this fully-integrated Dickson charge pump to bias sensor arrays where the noise typically produced by these converters currently restricts or prohibits their use.