Analog Devices Inc. LT8495HFE#PBF

Overview

LT8495HFE#PBF from Analog Devices is a monolithic SEPIC/boost/flyback DC/DC controller with integrated 2A/70V NPN power switch, programmable POR and watchdog timer, 9µA quiescent current in active operation, and dual supply pins (VIN/BIAS) enabling operation down to ~1V after startup. It targets automotive ECU power, portable product supplies, and industrial systems requiring wide input range and ultra-low IQ.

For engineers reviewing the LT8495HFE#PBF datasheet, LT8495HFE#PBF pinout, LT8495HFE#PBF application, or LT8495HFE#PBF equivalent, key selection criteria include its –40°C to 150°C operating junction temperature, fault-tolerant TSSOP-20 package, low-ripple Burst Mode® operation (<10mV output ripple), and independent capacitor-programmable reset/watchdog timing.

Technical Context

The LT8495HFE#PBF implements constant-frequency current-mode control with adjustable switching frequency (250kHz–1.5MHz via RT resistor), frequency foldback below 1V FB, and soft-start controlled by external SS capacitor. Its dual-supply architecture automatically selects the lower of VIN or BIAS for NPN base drive, enabling operation when VIN drops below 2.5V while maintaining regulation from BIAS.

Power-on reset and watchdog functions operate independently: RSTIN sets UVLO threshold (~1.1V reference) with tUV ≈ 23µs assertion delay, CPOR programs tRST (9.5ms typ.), and CWDT sets tWDU (16.7ms typ.) and tWDL (650µs typ.). Fault tolerance in TSSOP ensures adjacent pin shorts or opens do not raise output voltage above programmed value.

Key Specifications

Pinout & Package

LT8495HFE#PBF uses a 20-lead plastic TSSOP package with exposed pad (Pin 21 = GND), θJA = 38°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 DC/DC controller applications.

Compared with LTC3639EMSE#PBF and LT3958EUHE#PBF, the LT8495HFE#PBF uniquely integrates POR, watchdog, and fault-tolerant packaging in a high-temp TSSOP, making it optimal for automotive and industrial systems requiring self-contained supervision and extended temperature operation without external components.

Availability

LT8495HFE#PBF is available at Aetrix Electronics and suitable for automotive ECU power, portable medical device supplies, and industrial IoT sensor nodes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT8495HFE#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.

The LT8495 product line delivers highly integrated DC/DC controllers with system supervision for harsh-environment applications, emphasizing ultra-low quiescent current, wide input range, and functional safety features like FMEA-compliant packaging.

FAQ

What is the maximum input voltage supported by the LT8495HFE#PBF in SEPIC topology?

The LT8495HFE#PBF supports up to 60V input voltage in SEPIC topology, as specified in the Absolute Maximum Ratings and confirmed in the Applications Information section. This rating applies to the VIN pin and is independent of the BIAS supply. Operation above 60V risks permanent damage to the internal 70V-rated power switch.

How does the LT8495HFE#PBF achieve 9µA quiescent current, and under what conditions is this value valid?

The LT8495HFE#PBF achieves 9µA typical quiescent current from VIN when SWEN, WDE, and RSTIN are all held low (shutdown state), per Electrical Characteristics table. In active operation, its typical quiescent current is 3.1µA (LT8495H grade) at 12V VIN. The 9µA figure reflects deep shutdown-distinct from active low-power modes-and is validated across the –40°C to 150°C junction temperature range.

Can the LT8495HFE#PBF operate with input voltage below 2.5V, and how does the BIAS pin enable this?

Yes, the LT8495HFE#PBF can operate with VIN as low as ~1V after startup by drawing power from the BIAS pin. When VIN drops below 2.5V, the internal supply selector automatically switches to BIAS (typically connected to VOUT), allowing continued regulation even during deep battery discharge. This behavior is enabled by the dual-supply architecture and is documented in the Electrical Characteristics table under "Minimum VIN Operating Voltages".

What is the purpose of the NC pins on the LT8495HFE#PBF TSSOP package, and how should they be handled on the PCB?

The NC pins (Pins 4, 9, 17, 19) on the LT8495HFE#PBF TSSOP package are unconnected internally and must be left floating to preserve fault tolerance. Connecting them to GND, VIN, or other signals violates the FMEA design principle and may compromise the guaranteed overvoltage protection. The datasheet explicitly states these pins "must be left floating to ensure fault tolerance," and soldering them risks unintended current paths.

How are the reset timeout period (tRST) and watchdog timing parameters set on the LT8495HFE#PBF?

The reset timeout period tRST is set by capacitor CPOR on Pin 5: 4.7nF yields 9.5ms typical. Watchdog upper/lower boundaries (tWDU/tWDL) are set by capacitor CWDT on Pin 6: 1nF yields 16.7ms/650µs typical. These timings are linearly proportional to capacitance, as verified in Figures G21–G22. Values must match datasheet-specified tolerances (±10% for timing caps) to meet guaranteed specifications.