Analog Devices Inc. LT4356HDE-3#PBF

Overview

LT4356HDE-3#PBF from Analog Devices is a high-voltage surge stopper IC that protects downstream loads by regulating output voltage during overvoltage transients (e.g., automotive load dump) via external N-channel MOSFET gate control. It features 4V–80V operating range, 50mV overcurrent sense threshold, –40°C to 125°C temperature rating, and latchoff fault timer with early warning FLT output. Used in automotive power distribution systems requiring robust transient immunity.

For engineers reviewing the LT4356HDE-3#PBF datasheet, LT4356HDE-3#PBF pinout, LT4356HDE-3#PBF application, or LT4356HDE-3#PBF equivalent, key selection considerations include its adjustable output clamp voltage, reverse input protection to –60V, shutdown current <7µA, fault timer scalability via TMR capacitor, and AEC-Q100 qualification for under-hood deployment.

Technical Context

The LT4356HDE-3#PBF integrates dual protection loops: an overvoltage servo amplifier controlling GATE to maintain 1.25V at FB (enabling adjustable clamp), and an overcurrent sense amplifier limiting ΔVSNS to 50mV between VCC and SNS. Both faults charge the TMR capacitor with voltage-dependent current-scaling from 2µA to 50µA (OV) or 4µA to 260µA (OC)-to dynamically align fault timing with MOSFET safe operating area (SOA).

Its internal charge pump ensures ≥10V gate drive above OUT for standard-threshold N-MOSFETs above 8V VCC, while supporting logic-level devices down to 4V. The SHDN pin tolerates –60V to 100V and latches all circuitry into <7µA shutdown, including the auxiliary amplifier. Fault recovery requires SHDN pulse (<100µs low, then >10V/ms rise).

Key Specifications

Pinout & Package

LT4356HDE-3#PBF is housed in a 12-lead 4mm × 3mm plastic DFN package with exposed pad (Pin 13), rated for θ_JA = 43°C/W. The exposed pad may be left floating or connected to PCB ground for improved thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar surge protection applications.

Compared with LT4356IDE-3#PBF, the LT4356HDE-3#PBF extends operational temperature and adds AEC-Q100 qualification for harsh environments; versus TPS26631PWPR, it provides full overvoltage regulation, SOA-aware fault timing, and flexible auxiliary functions-making it essential for mission-critical automotive and industrial power integrity.

Availability

LT4356HDE-3#PBF is available at Aetrix Electronics and suitable for automotive load dump protection, hot-swap power distribution, and battery-powered reverse polarity protection requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT4356HDE-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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving automotive, industrial, communications, and healthcare markets with reliability-engineered components.

The LT4356 family is designed specifically for high-voltage transient protection in automotive and industrial power systems, delivering regulated output clamping, adaptive fault timing, and integrated auxiliary functions to replace discrete protection circuits.

FAQ

What is the maximum allowable voltage on the SHDN pin of the LT4356HDE-3#PBF?

The SHDN pin of the LT4356HDE-3#PBF withstands voltages from –60V to 100V relative to GND without damage. This allows direct connection to battery rails in reverse-battery or load-dump scenarios. Internal protection circuitry ensures functionality remains intact across this full range, and the 7µA internal pull-up simplifies interface design. Always verify external pull-up strength if leakage exceeds 1µA.

How does the LT4356HDE-3#PBF adjust its fault timer based on MOSFET stress?

The LT4356HDE-3#PBF scales TMR charging current with V_DS (VCC – OUT), ranging from 2µA at 0.5V to 260µA at 80V. During overvoltage, current rises to 50µA; during overcurrent, it reaches 260µA-ensuring faster shutdown under higher power dissipation. This dynamic scaling keeps MOSFET operation within its safe operating area (SOA), unlike fixed-timer solutions. The relationship is documented in Figures 1 and 2 of the LT4356-3 datasheet Rev F.

Can the LT4356HDE-3#PBF be used with a P-channel MOSFET instead of an N-channel device?

No-the LT4356HDE-3#PBF is specifically designed to drive N-channel MOSFETs with its charge-pump-based GATE output referenced to OUT. It lacks the high-side gate drive architecture needed for P-channel devices. Using a P-MOSFET would require external level-shifting and defeat the IC's integrated protection logic. For P-MOSFET applications, consider dedicated high-side switches like the LTC4412 or discrete solutions.

What is the purpose of the auxiliary amplifier in the LT4356HDE-3#PBF, and how is it configured?

The auxiliary amplifier in the LT4356HDE-3#PBF has its inverting input tied to an internal 1.25V reference and IN+ as the non-inverting input. It can be configured as a comparator (e.g., battery undervoltage detection) or as a linear regulator controller driving an external PNP pass transistor. AOUT provides open-collector output sinking up to 2mA. Unused IN+ must be grounded; AOUT requires external pull-up for logic-level interfacing.

How is the LT4356HDE-3#PBF reset after a latchoff fault condition?

After a latchoff fault, the LT4356HDE-3#PBF requires an active SHDN reset: pull SHDN low for at least 100µs, then raise it with a slew rate exceeding 10V/ms. Simply removing power is insufficient unless VCC drops below UVLO and remains off >100µs. During reset, the TMR capacitor must discharge to ~0.5V (via 2.2µA internal sink) to ensure reliable re-engagement. Failure to meet timing or slew-rate specs results in persistent GATE disable.