An Auto-Reconfigurable Multi-Output Regulating Switched-Capacitor DC–DC Converter for Wireless Power Reception and Distribution in Multi-Unit Implantable Devices

Abstract

An automatically reconfigurable switched-capacitor DC-DC converter with multiple regulated outputs is presented for wireless-powered multi-unit implantable medical devices (IMDs). In such devices, the main controller unit is powered wirelessly and provides supply voltages to the circuits of the main unit as well as multiple connected sub-units. The proposed DC-DC converter simultaneously generates two regulated voltages for the main unit and two unregulated voltages for the sub-units, which have on-site low-dropout regulators. The converter consists of i) an input-adaptive DC-DC conversion stage with two switched-capacitor (SC) DC-DC converters in series and ii) a regulating stage. In the DC-DC conversion stage, the proposed converter automatically reconfigures the conversion ratio and connection order of the two SC DC-DC converters and selects the output nodes by load selection switches depending on the input level. Thanks to these adaptive configurations, the proposed converter offers high conversion efficiencies over a wide input voltage range even with fewer flying capacitors required for the reconfigurable conversion ratios. Moreover, the selection switches are reused to regulate the output voltages to desired levels, minimizing the overhead for subsequent regulation. The IC fabricated in a 180-nm standard CMOS process achieves a conversion efficiency of 95.5% for the unregulated voltages and up to 77.4% for the regulated voltages over a wide input range of 1 V to 4 V with 0.74-mV output ripple for a load current of 20 mA, while providing four outputs (2 regulated, 2 unregulated).

Keywords

• Switched-capacitor DC-DC converter
• wide input voltage range
• small output ripple
• multiple outputs
• load selection
• reconfigurable conversion ratio