Ultra-low-noise LDOs cut wideband systems phase noise

November 07, 2013 // By Graham Prophet
Low-dropout regulators designed for use in wideband communication systems reduce LDO noise spectral density by a factor of two, provide the lowest phase noise for powering VCOs yielding the lowest jitter performance; and are suitable for powering clock devices in microwave systems.

Analog Devices' ADM7150/1 operate from 4.5 to 16V, provide up to 800 mA of output current and support output voltages from 1.5 to 5.0V. The LDOs achieve an output-NSD (noise spectral density) of 1.4 nV/ Hz from 10 kHz to 1 MHz, which significantly reduces VCO (voltage-controlled oscillator) phase noise in point-to-point microwave radios, satellite communications, defence electronics and other wideband applications. Additionally, a user adjustable CBYP can reduce low frequency 1/f noise (8 nV/ Hz at 100 Hz) for precision analog front-end measurement systems.

In addition to ultra-low noise, the ADM7150/1 achieve line and load transient responses of 0.01%/V and 0.4%/A respectively with a 10-µF ceramic output capacitor. The new LDOs also feature high PSRR (power-supply rejection ratio) performance of greater than 90 dB from 1 kHz to 100 kHz, and greater than 60 dB at 1 MHz. This effectively filters DC-DC switching regulator ripple, saving space by minimising the size of discrete filtering components normally needed.

In 3 x 3-mm, 8-lead LFCSP and SOIC, the parts cost $3.64 (1000).

Analog Devices; www.analog.com/ADM7150 / www.analog.com/ADM7151