Analog Devices Inc. LT4356CDE-2#PBF

Overview

LT4356CDE-2#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) and limiting current via external N-channel MOSFET gate control. It features 4V–80V operating range, 50mV overcurrent sense threshold, 1.25V FB reference, and operates from 0°C to 70°C in a 12-pin DFN package.

For engineers reviewing the LT4356CDE-2#PBF datasheet, LT4356CDE-2#PBF pinout, LT4356CDE-2#PBF application, or LT4356CDE-2#PBF equivalent, key selection considerations include shutdown quiescent current (60µA), auxiliary amplifier availability during shutdown, adjustable fault timer, reverse input protection to –60V, and guaranteed operation up to 125°C junction temperature.

Technical Context

The LT4356CDE-2#PBF integrates dual protection loops: an overvoltage servo loop that regulates GATE to maintain 1.25V at FB (setting clamped output), and an overcurrent loop that limits V_CC–V_SNS to 50mV. Both faults charge the TMR capacitor with voltage-dependent current-up to 50µA during overvoltage and 260µA during overcurrent-to enforce SOA-aware timing.

Unlike the LT4356-1 variant, the LT4356CDE-2#PBF retains its internal 1.25V reference and auxiliary amplifier active in shutdown mode (I_SHDN = 60µA), enabling undervoltage lockout or always-on regulation functions. Its SHDN pin tolerates –60V to +100V, and GATE drive is clamped to V_OUT + 14V with ±150mA pull-down capability.

Key Specifications

Pinout & Package

LT4356CDE-2#PBF is housed in a 12-lead (4mm × 3mm) plastic DFN package with exposed pad (Pin 13), rated for 0°C to 70°C ambient operation. The exposed pad may be left floating or connected to GND for improved thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT4356CDE-1#PBF, the LT4356CDE-2#PBF trades 53µA higher shutdown current for retained auxiliary amplifier operation-enabling undervoltage monitoring or bias generation during standby. Versus LT4363IMS-2#PBF, it offers design flexibility via external MOSFET selection and dual-function auxiliary amplifier, at the cost of added component count.

Availability

LT4356CDE-2#PBF is available at Aetrix Electronics and suitable for automotive surge protection, hot-swap power supplies, and intrinsic safety barrier designs requiring stable component supply and long-term manufacturability.

Supply support for LT4356CDE-2#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 industrial, automotive, communications, and healthcare markets.

The LT4356 family is designed as high-voltage surge stoppers for mission-critical power systems-specifically targeting automotive load dump, industrial transient immunity, and hot-swap applications where continuous operation during faults is essential.

FAQ

What is the key functional difference between LT4356CDE-2#PBF and LT4356CDE-1#PBF?

The LT4356CDE-2#PBF maintains its internal 1.25V reference and auxiliary amplifier active during shutdown (I_Q = 60µA), enabling undervoltage lockout or always-on bias generation. In contrast, the LT4356CDE-1#PBF disables all functional blocks in shutdown (I_Q = 7µA). This makes LT4356CDE-2#PBF suitable for systems requiring wake-up signaling or auxiliary regulation during low-power states.

How does the LT4356CDE-2#PBF protect against reverse input voltage?

The LT4356CDE-2#PBF supports reverse input protection to –60V on VCC and SHDN pins without damage. It allows implementation of back-to-back N-channel MOSFETs instead of a Schottky diode, reducing forward voltage drop and power loss. The SNS pin also tolerates –60V relative to VCC (within 30V differential limit), supporting robust current sensing in bidirectional configurations.

Can the LT4356CDE-2#PBF regulate output voltage to a user-defined level?

Yes. The LT4356CDE-2#PBF regulates output voltage by servoing the FB pin to 1.25V. A resistive divider from OUT to GND sets the clamp voltage-for example, R1 = 102kΩ and R2 = 4.99kΩ yields ~27V. The FB pin is internally clamped to 7V, and the regulation loop remains active during overvoltage transients, allowing precise, adjustable output clamping.

What determines the fault timer duration in LT4356CDE-2#PBF?

The fault timer duration in LT4356CDE-2#PBF is set by the capacitor connected from TMR to GND and modulated by voltage-dependent current. During overvoltage, TMR current ranges from ~2µA (at low V_DS) to 50µA (at 75V V_DS). During overcurrent, it scales from 4µA to 260µA (at 80V V_DS). This ensures shorter turn-off times under high-stress conditions, aligning with MOSFET safe operating area constraints.

Does LT4356CDE-2#PBF require external components for basic overvoltage protection?

Yes. For basic overvoltage protection, LT4356CDE-2#PBF requires an external N-channel MOSFET, FB resistive divider, TMR timing capacitor, and current sense resistor (for overcurrent). The TMR capacitor value directly sets fault timing (e.g., 6.8µF yields ~46ms total overvoltage fault time), and the FB divider defines the regulated output voltage.