Linear Technology debuts ultralow-noise 20-V, 500-mA LDO regulator
Milpitas, CA. Linear Technology Corp. has announced the LT3045 power-supply ripple-rejection (PSRR) low-dropout-voltage linear regulator—a higher output-current version of the vendor’s 200-mA LT3042 ultralow noise LDO. The LT3045’s design features ultralow spot noise of only 2 nV/√Hz at 10 kHz and 0.8 μV RMS integrated output noise across a 10-Hz to 100-kHz bandwidth. Low-frequency PSRR exceeds 90 dB out to 10 kHz, and high-frequency PSRR exceeds 70 dB out to 2.5 MHz, thereby quieting noisy or high ripple input supplies.
The LT3045 utilizes the vendor’s proprietary LDO architecture—a precision current-source reference followed by a 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 LT3045s to further decrease noise, increase output current and spread heat on a printed circuit board.
The LT3045 delivers up to 500-mA output current with a 260-mV dropout voltage at full load, across a wide 1.8-V to 20-V input voltage range. Output voltage range is 0 to 15 V, and output voltage tolerance is ±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 suitable for powering noise-sensitive medical imaging and diagnostics applications.
The LT3045 operates with a small, low-cost, 10-μF 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 a large value SET pin capacitor is used) and a power-good flag with programmable threshold to indicate output voltage regulation.
The LT3045 is available in thermally enhanced 10-lead 3-mm x 3-mm DFN (pin-compatible with the LT3042) and 12-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°C to 125°C. A future high-temperature H-grade version will be rated from -40°C to 150°C. Devices are in stock, priced starting at $2.80 each for the E-grade in 1,000-piece quantities.
