RF digital step attenuator gets performance boost for advanced wireless designs

April 24, 2014 // By Graham Prophet
Peregrine Semiconductor’s UltraCMOS PE4312 DSA is a successor to the PE4302 for wide dynamic-range network-infrastructure designs that require highly accurate and efficient amplitude control.

This DSA (digital step attenuator) upgrade is suitable for wireless-infrastructure devices, broadband consumer and infrastructure equipment, land mobile radios (LMRs), test-and-measurement equipment and military RF applications. The PE4312 is the only available DSA, Peregrine claims, to meet a low insertion loss of 2.1 dB at 4 GHz at any power-supply level between 2.3V and 5.5V. It also handles the widest temperature range between -40 and 105C and supports both 1.8V and 3V control logic. Improvements over PE4302 include attenuation accuracy ±(0.15 + 2% of attenuation setting), linearity (IIP3 of 59 dBm) and switching speed (500 nsec). A novel architecture provides safe attenuation-state-transition behaviour, which prevents positive power spikes that occur during attenuation-state changes when RF input power is applied. This feature simplifies the digital-interface design, improves signal quality and prevents damage to power amplifier sub-assemblies.

PE4312 is a 50-ohm, 6-bit RF DSA with a 31.5 dB attenuation range in 0.5 dB steps. It maintains high linearity of +59 dBm IIP3 and monotonicity from 1 MHz through 4 GHz. Pin-for-pin compatible with the PE4302, the PE4312 DSA features multiple programming modes, including serial, direct parallel, and latched parallel, making it easy to design it into a wide range of systems. The PE4312 has high, monotonic attenuation performance of 0.5 dB up to 4 GHz, which improves instrument sensitivity and performance. Fast switching time of 500 nsec improves system response times. ESD protection of 1.5 kV HBM eases manufacturing and prolongs the life of the end product. The 1.8 V and 3 V control logic support makes it easy to integrate the DSA with the latest FPGAs. High integration in a single package eliminates the need for the discrete components and bias circuits that are required with pin-diode solutions, further easing design and reducing board space. The PE4312 also features an external negative supply option. Its packaging is 20-lead QFN, 4 x 4 mm and its is priced at $1.52 (10,000). Evaluation