Analog Devices Inc. LT3990IMSE-3.3#PBF

Overview

LT3990IMSE-3.3#PBF from Analog Devices is a 62V input, 350mA fixed-output step-down regulator with integrated boost and catch diodes, 2.5µA quiescent current at 12V_IN to 3.3V_OUT, low-ripple Burst Mode operation (<5mV_P-P), and power-good flag. It delivers regulated 3.3V output in automotive battery regulation and industrial power supply applications.

For engineers reviewing the LT3990IMSE-3.3#PBF datasheet, LT3990IMSE-3.3#PBF pinout, LT3990IMSE-3.3#PBF application, or LT3990IMSE-3.3#PBF equivalent, key selection criteria include its 3.3V fixed output, 16-pin MSOP package with exposed thermal pad, –40°C to 125°C operating range, AEC-Q100 qualification, and integrated diode architecture eliminating external Schottky requirements.

Technical Context

The LT3990IMSE-3.3#PBF implements constant-frequency current-mode control with programmable switching frequency (200kHz–2.2MHz) via RT resistor. Its internal bipolar NPN switch and integrated boost/catch diodes enable high-efficiency operation across 4.2V–62V input range while maintaining stable regulation under transient load steps.

Burst Mode operation reduces quiescent current to 1.8µA at light loads while holding output ripple below 5mV_P-P; the power-good comparator asserts when V_OUT reaches 90% of 3.3V, and accurate undervoltage lockout (1.19V threshold, 35mV hysteresis) ensures reliable startup and shutdown behavior.

Key Specifications

Pinout & Package

LT3990IMSE-3.3#PBF uses a 16-lead plastic MSOP package with exposed thermal pad (Pin 17 = GND). The package is thermally enhanced for high-power-density buck conversion in constrained layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output buck regulator applications.

Compared with LTC3630EMSE-3.3#PBF and TPS63020DSJR, the LT3990IMSE-3.3#PBF uniquely combines 62V input tolerance, integrated diodes, AEC-Q100 Grade I qualification, and sub-3µA quiescent current-making it the only direct fit for automotive and high-reliability industrial 3.3V point-of-load regulation.

Availability

LT3990IMSE-3.3#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial sensor power supplies, and portable medical device power requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.

Supply support for LT3990IMSE-3.3#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving industrial, automotive, communications, and healthcare markets.

The LT3990 product line delivers high-voltage, low-quiescent-current buck regulators with integrated diodes for automotive and industrial power conversion-designed to replace discrete solutions while meeting stringent reliability and qualification standards.

FAQ

What is the guaranteed output voltage accuracy of the LT3990IMSE-3.3#PBF over temperature?

The LT3990IMSE-3.3#PBF guarantees 3.3V output within ±1.2% over its full operating junction temperature range of –40°C to 125°C, as specified in the Electrical Characteristics table (min/max values of 3.26V to 3.34V at I_LOAD = 100mA). This accuracy is achieved via factory-trimmed internal feedback resistors and does not require external calibration.

Does the LT3990IMSE-3.3#PBF require external diodes for operation?

No, the LT3990IMSE-3.3#PBF integrates both the boost diode and catch diode on-die. This eliminates the need for external Schottky diodes typically required in high-voltage buck converters, reducing component count, board area, and thermal design complexity. The internal diodes are rated for 450mA valley current (catch) and support full 350mA output capability.

How does the LT3990IMSE-3.3#PBF achieve low output ripple in Burst Mode operation?

The LT3990IMSE-3.3#PBF achieves <5mV_P-P output ripple in Burst Mode through optimized internal compensation, precise burst timing control, and low-noise gate drive. Unlike conventional burst-mode regulators, its architecture minimizes energy per burst and controls burst frequency to avoid audio-band excitation of output capacitors-critical for noise-sensitive applications like medical instrumentation.

What is the minimum input voltage required for the LT3990IMSE-3.3#PBF to regulate 3.3V output?

The LT3990IMSE-3.3#PBF requires a minimum input voltage of 4.2V to operate, as defined by its absolute minimum operating voltage. At higher switching frequencies, the practical minimum may increase due to duty-cycle limitations; for example, at 2.2MHz, VIN(MIN) ≈ 5.0V (calculated using t_OFF(MIN) = 160ns). Full 350mA output is supported down to 4.2V input only at frequencies ≤1MHz.

Is the LT3990IMSE-3.3#PBF pin-compatible with other variants in the LT3990 family?

Yes, the LT3990IMSE-3.3#PBF shares identical pinout and package (16-lead MSOP) with all other LT3990-XMSE variants (e.g., LT3990IMSE-5#PBF, LT3990EMSE#PBF). Pin functions-including dual VOUT pins (1 & 2), EN/UVLO (Pin 4), and PG (Pin 14)-are functionally identical across the family, enabling drop-in replacement for different output voltages or temperature grades without PCB redesign.