Analog Devices Inc. LTC3639MPMSE#PBF

Overview

LTC3639MPMSE#PBF from Analog Devices (formerly Linear Technology) is a high-efficiency, 150V input synchronous step-down DC/DC regulator with integrated high-side P-channel and low-side N-channel MOSFETs, delivering up to 100mA output current, 12µA no-load quiescent current, and programmable peak current limit (17–230mA). It operates across –55°C to 150°C and supports fixed 1.8V/3.3V/5V or adjustable 0.8V–VIN outputs in industrial control and avionics power supplies.

For engineers reviewing the LTC3639MPMSE#PBF datasheet, LTC3639MPMSE#PBF pinout, LTC3639MPMSE#PBF application, or LTC3639MPMSE#PBF equivalent, key selection considerations include its 150V absolute max input rating, thermally enhanced MSE-16 package with exposed GND pad, Burst Mode® operation for ultra-low IQ, precise RUN/OVLO thresholds, and internal soft-start with 1ms default ramp time.

Technical Context

The LTC3639MPMSE#PBF implements a hysteretic Burst Mode® control architecture that alternates between active burst cycles-where the internal P-channel high-side and N-channel low-side MOSFETs switch-and sleep cycles where both switches are off and only 12µA is drawn. Its feedback comparator uses a 0.800V ±1% reference with 5mV hysteresis to trigger burst initiation when VFB falls below 0.795V.

Peak inductor current is set via an external resistor on ISET (5µA current source), directly scaling the 20–200mA threshold linearly; maximum average output current is half the programmed peak current. The RUN and OVLO pins each feature 110mV internal hysteresis and operate as precision voltage comparators referenced to 1.21V rising threshold, enabling robust undervoltage and overvoltage lockout with graceful soft-start reset recovery.

Key Specifications

Pinout & Package

The LTC3639MPMSE#PBF is housed in a thermally enhanced 16-lead plastic MSOP (MSE) package with four missing pins (pins 2, 4, 13, 15), featuring an exposed GND pad (Pin 17) that must be soldered to PCB ground for thermal performance (θJC = 10°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous step-down regulator applications.

Compared with LTC3639HMSE#PBF and LTC3639IMSE#PBF, the LTC3639MPMSE#PBF uniquely guarantees full electrical performance across –55°C to 150°C, making it the only variant suitable for mission-critical aerospace, defense, and downhole electronics where extreme thermal margins are non-negotiable.

Availability

LTC3639MPMSE#PBF is available at Aetrix Electronics and suitable for industrial control supplies, avionics power systems, medical diagnostic equipment, and portable test instruments requiring stable component supply across extended temperature extremes.

Supply support for LTC3639MPMSE#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 and maintains its high-reliability power management portfolio with rigorous qualification standards.

The LTC3639MPMSE#PBF belongs to Linear's high-voltage monolithic DC/DC regulator family, designed specifically for ruggedized power conversion in aerospace, defense, and industrial environments where wide input range, extended temperature operation, and low quiescent current are mandatory.

FAQ

What is the absolute maximum input voltage rating for the LTC3639MPMSE#PBF?

The LTC3639MPMSE#PBF has an absolute maximum input voltage rating of 150V on the VIN pin, as specified in the Absolute Maximum Ratings table. This rating applies regardless of operating temperature or duty cycle and must not be exceeded to prevent permanent damage. Continuous operation is limited to 4V–150V, and the device includes programmable OVLO to disable switching before reaching this limit.

How does the LTC3639MPMSE#PBF achieve 12µA quiescent current at no load?

The LTC3639MPMSE#PBF achieves 12µA typical no-load quiescent current through Burst Mode® operation: during light loads, it enters sleep cycles where internal power switches and current comparators are disabled, leaving only essential bias circuitry active. This architecture minimizes average supply current while maintaining output regulation, and the 12µA value is measured at TA = 25°C with VIN = 12V and no load.

Can the LTC3639MPMSE#PBF be configured for a fixed 5V output without external resistors?

Yes, the LTC3639MPMSE#PBF can be configured for a fixed 5V output without external resistors by connecting VPRG1 to the SS pin and VPRG2 to GND. This activates an internal resistive divider that sets the feedback threshold to 5.015V (typical), enabling precise 5V regulation with zero external components beyond the inductor and capacitors.

What is the purpose of the exposed pad (Pin 17) on the LTC3639MPMSE#PBF package?

The exposed pad (Pin 17) on the LTC3639MPMSE#PBF is electrically and thermally connected to GND and must be soldered to the PCB ground plane. It reduces thermal resistance from junction to case (θJC = 10°C/W) and is essential for maintaining safe junction temperatures under full load, especially at high ambient temperatures or elevated input voltages.

How is peak inductor current programmed on the LTC3639MPMSE#PBF?

Peak inductor current on the LTC3639MPMSE#PBF is programmed using an external resistor (RISET) from the ISET pin to GND. A 5µA internal current source generates a voltage across RISET that scales the peak current threshold linearly: RISET = IPEAK × 10⁶ (for 20mA ≤ IPEAK ≤ 200mA). Leaving ISET floating yields 230mA typical; shorting to GND yields 25mA typical.