Analog Devices Inc. LT3695IMSE-3.3#PBF

Overview

LT3695IMSE-3.3#PBF from Analog Devices (formerly Linear Technology) is a fault-tolerant 1A monolithic buck switching regulator with fixed 3.3V output, 3.6V–36V input range, and 60V transient tolerance. It features low-ripple Burst Mode operation (<15mV_P-P), 75μA no-load quiescent current at 12V_IN/3.3V_OUT, and integrated power-good flag - deployed in automotive battery regulation and industrial distributed supplies.

For engineers reviewing the LT3695IMSE-3.3#PBF datasheet, LT3695IMSE-3.3#PBF pinout, LT3695IMSE-3.3#PBF application, or LT3695IMSE-3.3#PBF equivalent, key selection considerations include FMEA-compliant adjacent-pin-short immunity, thermal performance in the 16-pin MSOP package with exposed pad, synchronization capability (300kHz–2.2MHz), and fixed-output voltage accuracy (±1% over temperature).

Technical Context

The LT3695IMSE-3.3#PBF uses current-mode control with internal error amplifier (gm = 430μS, gain = 1300 V/V) and programmable oscillator (250kHz–2.2MHz via RT resistor). Its architecture includes frequency foldback during overload, DA-pin-based catch-diode current sensing for inductor current limiting, and VC-pin clamping to enforce peak switch current limits (1.45A typical, 2A max).

Fault tolerance is implemented via dedicated NC pins (3, 10, 12), open-pin-safe regulation, and independent PG monitoring of OUT1/OUT2 pins at 90% of 3.3V (±50mV hysteresis). Bias sourcing dynamically switches between VIN and OUT1/OUT2 when output exceeds 3V, reducing quiescent current and improving light-load efficiency.

Key Specifications

Pinout & Package

LT3695IMSE-3.3#PBF is housed in a thermally enhanced 16-lead plastic MSOP package with exposed pad (Pin 17) for improved θ_JA (40°C/W when soldered, 110°C/W unsoldered).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT3695EMSE-3.3#PBF, the LT3695IMSE-3.3#PBF guarantees full specification compliance down to –40°C, making it suitable for cold-climate automotive start-up; versus LT3695HMSE-3.3#PBF, it trades 150°C capability for lower cost while retaining identical fault tolerance and regulation accuracy across its –40°C to 125°C range.

Availability

LT3695IMSE-3.3#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial distributed supplies, and telecom point-of-load applications requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to +125°C operation.

Supply support for LT3695IMSE-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 and maintains its legacy precision power management portfolio with full technical and manufacturing continuity.

The LT3695 series was designed specifically for harsh-environment DC/DC conversion - emphasizing fault tolerance, transient resilience, and minimal external component count in automotive and industrial applications.

FAQ

What is the guaranteed operating temperature range for the LT3695IMSE-3.3#PBF?

The LT3695IMSE-3.3#PBF is guaranteed to meet all specifications over a junction temperature range of –40°C to +125°C. This I-grade qualification ensures reliable startup and regulation in automotive under-hood and industrial outdoor environments where ambient temperatures span extreme lows and highs. The device incorporates thermal shutdown and frequency foldback to protect against sustained overheating beyond this range.

How does the LT3695IMSE-3.3#PBF achieve fault tolerance during adjacent pin shorts?

The LT3695IMSE-3.3#PBF achieves FMEA-compliant fault tolerance through three design elements: (1) dedicated NC pins (3, 10, 12) that are internally unconnected and must remain floating; (2) internal regulation logic referenced solely to OUT1/OUT2, isolating feedback from compromised pins; and (3) output clamping architecture that prevents voltage rise above 3.3V even if SW, BOOST, or SYNC are shorted to adjacent terminals. This behavior is verified per manufacturer test conditions in the datasheet.

Can the LT3695IMSE-3.3#PBF be synchronized to an external clock, and what is the valid frequency range?

Yes, the LT3695IMSE-3.3#PBF supports external clock synchronization via the SYNC pin, accepting input frequencies from 300kHz to 2.2MHz. Clock edges must have rise/fall times faster than 1μs. When synchronized, the device maintains its internal current-mode control loop and Burst Mode functionality - but operates at the master clock frequency rather than its RT-set frequency. This enables EMI reduction in noise-sensitive systems.

What is the purpose of the DA pin on the LT3695IMSE-3.3#PBF, and how does it affect operation?

The DA pin on the LT3695IMSE-3.3#PBF senses current through the external Schottky catch diode. When diode current exceeds ~1.6A, the device initiates frequency foldback - reducing switching frequency to limit inductor peak current during overload or short-circuit events. This protects both the IC and external components without requiring additional current-sense circuitry, and is active regardless of SYNC mode or Burst Mode state.

Does the LT3695IMSE-3.3#PBF require an external feedback resistor network?

No, the LT3695IMSE-3.3#PBF does not require an external feedback resistor network because it is a fixed-output variant. Internal precision resistors set the regulated output to 3.3V, with feedback taken directly from the OUT1 and OUT2 pins. This eliminates resistor tolerance errors and simplifies layout - unlike the adjustable LT3695 base part, which requires an external FB divider referenced to the 0.8V internal reference.