A Dual Charge Pump for Quiescent Touch Sensor Power Supply

This brief presents a dual charge pump suitable for touch sensor power supply applications, where a calm standby voltage as well as quick recovery from disturbance is required. The proposed circuit adaptively controls the two parallel-connected charge pumps: a current driving Dickson's charge pump with a pumping capacitor of 95.4 pF and a low-ripple cross-couple charge pump with a capacitor of 10.6 pF. The heavy-duty Dickson's pump turns on for swift recovery from the drastic charge loss and turns off for reduced noise during the hold-and-sensing period. An instantaneous pumping stroke of the charge pump controller and a low dropout following the charge pumps further reduce supply noise. The proposed circuit is fabricated using a 0.18-μm CMOS process. Measurement results show a recharge time shorter than 1 μs and supply noise less than the detection limit. The area penalty is less than 1% compared to a single charge pump.