PSRR linear regulator's spot noise is only 2nV/√Hz at 10kHz

23rd February 2015

Barney Scott

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Datasheet

Linear has released the LT3042, a low noise, high Power Supply Ripple Rejection (PSRR) low dropout voltage linear regulator. Its design features low spot noise of only 2nV/√Hz at 10kHz and 0.8µV_RMS integrated output noise across a 10Hz to 100kHz bandwidth. Low frequency PSRR exceeds 90dB out to 10kHz and high frequency PSRR exceeds 75dB out to 3MHz, quieting noisy or high ripple input supplies.

The LT3042 utilises LTC’s proprietary LDO architecture, a precision current source reference followed by a high performance unity gain buffer, resulting in virtually constant bandwidth, noise, PSRR and load regulation performance independent of output voltage. In addition, this architecture permits paralleling of multiple LT3042s to further decrease noise, increase output current and spread heat on a PCB.

The LT3042 delivers up to 200mA output current with a 350mV dropout voltage at full load, across a 1.8-20V input voltage range. Output voltage range is 0-15V and output voltage tolerance is highly accurate at ±2% over line, load and temperature.

The device’s input and output voltage ranges, high bandwidth, high PSRR and low noise performance make it suitable for powering noise-sensitive applications such as PLLs, VCOs, mixers, LNAs, very low noise instrumentation, high speed/high precision data converters, medical applications such as imaging and diagnostics, precision power supplies and as a post regulator for switching supplies.

The LT3042 operates with a small, low cost, 4.7µF ceramic output capacitor, optimising stability and transient response. A single resistor programs the external precision current limit (±10% over temperature). A single SET pin capacitor lowers output noise and provides reference soft-start functionality, preventing output voltage overshoot at turn on.

The device’s internal protection circuitry includes reverse battery protection, reverse current protection, internal current limit with foldback and thermal limit with hysteresis. Other features include fast start-up capability (useful if large value SET pin capacitors are used) and a power good flag with programmable threshold to indicate output voltage regulation.

The LT3042 is available in thermally enhanced 10-lead 3x3mm DFN and 10-lead MSOP packages, both with a compact footprint. The E- and I-grade versions are available from stock with an operating junction temperature of -40 to +125°C. The high temperature H grade is rated from -40 to +150°C, and the high reliability MP-grade version is specified from -55 to +150°C. Devices are in stock, and pricing starts at $2.39 each for the E grade in 1,000-piece quantities.