Analog Devices Inc. LT3990IMSE#PBF

Overview

LT3990IMSE#PBF from Analog Devices is a 62V, 350mA monolithic step-down regulator with integrated boost and catch diodes, 2.5µA quiescent current at 12V_IN→3.3V_OUT, low-ripple Burst Mode operation (<5mV_P-P), and programmable undervoltage lockout (1.19V threshold). It serves as a primary DC/DC power stage in automotive battery regulation and industrial supplies requiring high input voltage tolerance and ultra-low standby power.

For engineers reviewing the LT3990IMSE#PBF datasheet, LT3990IMSE#PBF pinout, LT3990IMSE#PBF application, or LT3990IMSE#PBF equivalent, key selection criteria include its 16-pin MSOP thermal performance (θ_JA = 40°C/W), FMEA-fault-tolerant pin architecture, 200kHz–2.2MHz adjustable switching frequency, and AEC-Q100 qualification for automotive use.

Technical Context

The LT3990IMSE#PBF implements constant-frequency current-mode control with internal bipolar NPN switch, integrated boost and catch Schottky diodes, and dual current limiting (switch peak: 700mA typ; catch valley: 450mA typ). Its error amplifier regulates FB to 1.21V (or VOUT directly for fixed-output variants) and drives VC to modulate duty cycle via slope compensation.

Burst Mode operation disables non-essential circuitry between switching bursts to achieve 1.8µA no-load supply current, while maintaining output ripple below 5mV_P-P. Power Good (PG) asserts when FB reaches 90% of regulation voltage, and EN/UVLO provides accurate 1.19V rising threshold with 35mV hysteresis-valid only when VIN ≥ 4.2V.

Key Specifications

Pinout & Package

LT3990IMSE#PBF uses a 16-lead plastic MSOP package with exposed thermal pad (Pin 17 = GND), θ_JA = 40°C/W, θ_JC = 10°C/W. The exposed pad must be soldered to PCB for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3639EMSE#PBF and TPS54340DDAR, LT3990IMSE#PBF uniquely combines 62V input, 350mA output, integrated diodes, and 2.5µA I_Q in a compact MSOP - making it optimal for space-constrained, battery-sensitive automotive and industrial edge nodes where component count and standby power are critical.

Availability

LT3990IMSE#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial sensor node power, and ruggedized portable equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT3990IMSE#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 automotive, industrial, and communications markets with precision, reliability, and longevity.

The LT3990 product line delivers high-voltage, low-quiescent-current buck regulators optimized for automotive and industrial applications demanding AEC-Q100 qualification, FMEA robustness, and integrated power stage simplicity.

FAQ

What is the guaranteed operating temperature range for LT3990IMSE#PBF?

The LT3990IMSE#PBF is guaranteed over the full –40°C to +125°C junction temperature range. This I-grade rating ensures parametric performance compliance across automotive cabin and industrial control environments without derating. The device uses internal thermal shutdown and current limiting to protect against sustained overtemperature conditions, and its MSOP package with exposed pad achieves θ_JA = 40°C/W with proper PCB copper area.

Does LT3990IMSE#PBF require external diodes for operation?

No, LT3990IMSE#PBF integrates both the boost diode and catch Schottky diode on-die. This eliminates two external components, reduces board area, and improves reliability by removing solder joint and packaging failure points. The integrated catch diode supports up to 450mA valley current, and the boost diode sustains up to 12mA drive current - sufficient for typical 33nF–100nF bootstrap capacitors used with the internal bipolar NPN switch.

How does the Power Good (PG) pin function on LT3990IMSE#PBF?

The PG pin on LT3990IMSE#PBF is an open-drain output that remains low until the FB pin reaches 90% of its final regulated voltage (e.g., 1.089V for 1.21V reference). PG becomes valid only when VIN > 4.2V and EN/UVLO is high. It requires an external pull-up resistor to a logic-compatible voltage (e.g., 3.3V or 5V) and sinks up to 80µA when asserted low. This signal enables safe processor reset sequencing and system-level power monitoring.

Can LT3990IMSE#PBF be used in Burst Mode with ceramic output capacitors?

Yes, LT3990IMSE#PBF supports Burst Mode operation with ceramic output capacitors, but audible noise may occur at light loads due to piezoelectric excitation. The device's low 1.8µA no-load current and <5mV_P-P ripple make ceramics viable for most applications; however, if acoustic noise is unacceptable (e.g., medical or audio equipment), a high-performance tantalum or polymer capacitor is recommended for the output stage.

What is the minimum input voltage required for LT3990IMSE#PBF to regulate a 5V output?

The minimum input voltage for LT3990IMSE#PBF to regulate 5V depends on switching frequency and duty cycle limits. At 400kHz, the minimum VIN is approximately 6.5V to start and 5.0V to sustain regulation - derived from V_IN(MIN) = (V_OUT + V_D) / (1 − f_SW × t_OFF(MIN)) − V_D + V_SW, where V_D ≈ 0.7V and t_OFF(MIN) = 160ns. Below 4.2V, the part cannot operate regardless of frequency.