Ultra low-noise ultra-high PSRR LDO for noise-sensitive applications

24-02-2015 | Linear | Power

Linear Technology has introduced the LT3042, a progressive ultra low-noise, ultra-high power supply ripple rejection (PSRR) low dropout voltage linear regulator. The device's novel design features ultra-low spot noise of only 2nV/vHz at 10kHz and 0.8µVRMS integrated output noise across a wide 10Hz to 100kHz bandwidth.

Low and high frequency PSRR performance are exceptional. 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 utilizes 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 printed circuit board.

The LT3042 delivers up to 200mA output current with a 350mV dropout voltage at full load, across a wide 1.8V to 20V input voltage range. Output voltage range is 0V to 15V and output voltage tolerance is highly accurate at ±2% over line, load and temperature. The device’s wide input and output voltage ranges, high bandwidth, high PSRR and ultralow noise performance make it ideal 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, optimizing 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. Moreover, 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 3mm x 3mm 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 -40C to 125C. The high temperature H grade is rated from -40C to 150C, and the high reliability MP-grade version is specified from -55C to 150C, says the company.

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