20V, 500mA LDO with Ultralow (0.8μVRMS) Noise & 76dB PSRR at 1MHz Powers Noise-Sensitive Applications

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LT3045 Linear Technology Corporation announces the LT3045, an ultralow noise, ultrahigh power supply ripple rejection (PSRR) low dropout voltage linear regulator, a higher output current version of the widely accepted 200mA LT3042 ultralow noise LDO. The LT3045’s unique design features ultralow spot noise of only 2nV/√Hz 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 70dB out to 2.5MHz, thereby quieting noisy or high ripple input supplies. The LT3045 utilizes Linear’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 LT3045s to further decrease noise, increase output current and spread heat on a printed circuit board.

The LT3045 delivers up to 500mA output current with a 260mV 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 are 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 LT3045 operates with a small, low cost, 10μF 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 3mm x 3mm 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. For more information, visit www.linear.com/product/LT3045.

Summary of Features: LT3045

Ultralow RMS Noise: 0.8μVRMS (10Hz to 100kHz)
Ultralow Spot Noise: 2nV/√Hz at 10kHz
Ultrahigh PSRR: >90dB to 10kHz & >70dB to 2.5MHz
Output Current: 500mA
Wide Input Voltage Range: 1.8V to 20V
Single Capacitor Improves Noise & PSRR
100μA SET Pin Current: ±1% Initial Accuracy
Single Resistor Programs Output Voltage
High Bandwidth: 1MHz
Programmable Current Limit
Low Dropout Voltage: 260mV
Output Voltage Range: 0V to 15V
Power Good Flag with Programmable Threshold
Fast Start-Up Capability
Precision Enable/UVLO
Can Be Paralleled for Lower Noise & Higher Current
Internal Current Limit with Foldback
Minimum Output Capacitor: 10μF Ceramic
Reverse-Battery & Reverse-Current Protection
12-Lead MSOP & 10-Lead 3mm x 3mm DFN Packages
Pricing shown is for budgetary use only and may differ due to local duties, taxes, fees and exchange rates.

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