説明

The LT3042 is a high performance low dropout linear regulator featuring LTC’s ultralow noise and ultrahigh PSRR architecture for powering noise sensitive RF applications. Designed as a precision current reference followed by a high performance voltage buffer, the LT3042 can be easily paralleled to further reduce noise, increase output current and spread heat on the PCB.

The device supplies 200mA at a typical 350mV dropout voltage. Operating quiescent current is nominally 2mA and drops to <<1μA in shutdown. The LT3042’s wide output voltage range (0V to 15V) while maintaining unitygain operation provides virtually constant output noise, PSRR, bandwidth and load regulation, independent of the programmed output voltage. Additionally, the regulator features programmable current limit, fast start-up capability and programmable power good to indicate output voltage regulation.

The LT3042 is stable with a minimum 4.7μF ceramic output capacitor. Built-in protection includes reverse battery protection, reverse current protection, internal current limit with foldback and thermal limit with hysteresis. The LT3042 is available in thermally enhanced 10-Lead MSOP and 3mm × 3mm DFN packages.

 

特徴

Ultralow RMS Noise: 0.8μVRMS (10Hz to 100kHz)

Ultralow Spot Noise: 2nV/√Hz at 10kHz

Ultrahigh PSRR: 79dB at 1MHz

Output Current: 200mA

Wide Input Voltage Range: 1.8V to 20V

Single Capacitor Improves Noise and PSRR

100μA SET Pin Current: ±1% Initial Accuracy

Single Resistor Programs Output Voltage

High Bandwidth: 1MHz

Programmable Current Limit

低入出力電圧：350mV

Output Voltage Range: 0V to 15V

Programmable Power Good

Fast Start-Up Capability

Precision Enable/UVLO

Parallelable for Lower Noise and Higher Current

Internal Current Limit with Foldback

Minimum Output Capacitor: 4.7μF Ceramic

Reverse Battery and Reverse Current Protection

10-Lead MSOP and 3mm × 3mm DFN Packages

AEC-Q100 Qualified for Automotive Applications

 

アプリケーション

RF Power Supplies: PLLs, VCOs, Mixers, LNAs

Very Low Noise Instrumentation

High Speed/High Precision Data Converters

Medical Applications: Imaging, Diagnostics

Precision Power Supplies

Post-Regulator for Switching Supplies

 

アプリケーション情報

The LT3042 is a high performance low dropout linear regulator featuring LTC’s ultralow noise (2nV/√Hz at 10kHz) and ultrahigh PSRR (79dB at 1MHz) architecture for powering noise sensitive applications. Designed as a precision current source followed by a high performance rail-to-rail voltage buffer, the LT3042 can be easily paralleled to further reduce noise, increase output current and spread heat on the PCB. The device additionally features programmable current limit, fast start-up capability and programmable power good. The LT3042 is easy to use and incorporates all of the protection features expected in high performance regulators. Included are short-circuit protection, safe operating area protection, reverse battery protection, reverse current protection, and thermal shutdown with hysteresis.

Protection Features

The LT3042 incorporates several protection features for battery-powered applications. Precision current limit and thermal overload protection protect the LT3042 against overload and fault conditions at the device’s output. For normal operation, do not allow the junction temperature to exceed 125°C (E-, I-grade) or 150°C (H-, MP-grade).

To protect the LT3042’s low noise error amplifier, the SETto- OUTS protection clamp limits the maximum voltage between SET and OUTS with a maximum DC current of 20mA through the clamp. So for applications where SET is actively driven by a voltage source, the voltage source must be current limited to 20mA or less. Moreover, to limit the transient current flowing through these clamps during a transient fault condition, limit the maximum value of the SET pin capacitor (CSET) to 22μF.

The LT3042 also incorporates reverse input protection whereby the IN pin withstands reverse voltages of up to –20V without causing any input current flow and without developing negative voltages at the OUT pin. The regulator protects both itself and the load against batteries that are plugged-in backwards.

In circuits where a backup battery is required, several different input/output conditions can occur. The output voltage may be held up while the input is either pulled to GND, pulled to some intermediate voltage, or left opencircuit. In all of these cases, the reverse current protection circuitry prevents current flow from output to the input. Nonetheless, due to the OUTS-to-SET clamp, unless the SET pin is floating, current can flow to GND through the SET pin resistor as well as up to 15mA to GND through the output overshoot recovery circuitry. This current flow through the output overshoot recovery circuitry can be significantly reduced by placing a Schottky diode between OUTS and SET pins, with its anode at the OUTS pin.