High voltage LDMOS inverter for on-chip RF-MEMS actuation

In this work, two high voltage LDMOS inverters, a charge pump and a differential ring oscillator are designed and combined with a Ka-band RF-MEMS SPDT (single-pole double-throw) switch in a single BiCMOS chip. The circuit is fabricated in a triple well 0.25 μm SiGe:C BiCMOS process which includes a LDMOS- and a RF-MEMS module. The measured rise and fall times of the high voltage inverter are below 2.5 μs and 2 μs considering a 65 pF capacitor in parallel with a 1 MO resistor as the load caused by the measurement setup. Simulations based on the RF-MEMS electrode capacitance of ∼200fF — as the real case application — result in a drastically decreased rise (charge) time and fall (discharge) time of 10 ns and 8 ns, respectively. The maximum operating voltage of the LDMOS inverter is 45 V, which enables the actuation of the RF-MEMS switch. The measured S-parameters of the RF-MEMS SPDT switch, driven by the developed LDMOS inverters and charge pump, demonstrate the successful implementation.