Peregrine launches digitally tunable capacitors

Silicon-on-sapphire tunable capacitors for integrating into RF systems 
By Nick Flaherty www.flaherty.co.uk

Peregrine Semiconductor has developed a family of 5bit, 32-state digitally controlled variable capacitor to provide a monolithically integrated impedance tuning for RF applications. The PE64904 and PE64905 DuNE Digitally Tunable Capacitors (DTCs) enable wide-band tunable networks, minimizing mismatch losses, improving system efficiency and reducing radio complexity for a cost-effective tuning solution. Design applications for the new DTC devices range from tunable filters and matching networks to RFID, antenna tuning and other wireless communications where tunability and optimal system performance is critical.
“The need for a monolithically integrated, easy-to-use impedance tuning device has never been greater, and we are pleased to commercially release these new devices,” said Mark Schrepferman, marketing director for Peregrine’s HPS business unit. “Our initial DuNE technology launch enabled prototype DTCs for cellular handset and mobile TV applications. In identifying the performance requirements of the broader market, Peregrine engineers designed the latest DTCs to address a wide variety of complex tunable architectures,” he added.
The versatile solid-state devices can be used in Series or Shunt configurations to support a wide variety of tuning circuit topologies. Capacitance range is 0.7-4.6 pF in discrete 126 fF steps (6.6:1 tuning ratio) in Series configuration, and 1.1-5.1 pF in discrete 131 fF steps (4.6:1 tuning ratio) in Shunt configuration. The Quality Factor (Q) for a Shunt-configured DTC is ~35 for lowest capacitance state (at 1 GHz).
To address the requirements of peripheral interface programming, both 3-wire SPI-compatible (PE64904) and 2-wire I2C-compatible (PE64905) serial control versions are available. These interface options allow multiple DTCs to be controlled by a single serial interface. I2C programming interface is further described in Peregrine’s AN28 application note.
Both devices are manufactured on Peregrine’s UltraCMOS silicon-on-sapphire (SOS) process technology which optimize the devices’ high RF power handling (>+38 dBm @ 50 Ω, 30 Vpk RF); wide power supply range (2.3-3.6V); low current consumption (typ. 140 μA at 2.6V); built-in bias voltage generation and exceptional 2kV HBM ESD tolerance on all pins. The new DTCs maintain excellent linearity: IIP2 is +105 dBm and IIP3 is +65 dBm (typ) across a wide operating range of 100 MHz to 3 GHz, and, as with all UltraCMOS-based devices, the DTCs are immune to latch-up. The Company’s HaRP™ technology design enhancements have been applied to deliver excellent harmonic performance of 75 dBc (2fo and 3fo) across the tuning range; fast 12 μs switching time; 10 μs settling time; and low-power operation (140 μA).
The PE64904 and PE64905, scheduled for volume production in Q3 2011, are housed in 2x2mm 10-lead QFN packages and priced at $1.45 each (10K units). Evaluation Kits for each device, which are designed for accurate DTC impedance measurement and loss, include cables and USB interface board and are priced at $168.00 each.