Analog Devices Inc. LT8357HMSE#PBF

Overview

LT8357HMSE#PBF from Analog Devices is a wide-input, current-mode DC/DC controller supporting boost, SEPIC, and flyback topologies. It features 3V–60V input range, 2MHz max switching frequency, 8µA Burst Mode® quiescent current, ±1.5% internal 1V reference, and 5V split gate drive for MOSFETs. It is AEC-Q100 qualified and used in automotive powertrain battery monitoring systems.

For engineers reviewing the LT8357HMSE#PBF datasheet, LT8357HMSE#PBF pinout, LT8357HMSE#PBF application, or LT8357HMSE#PBF equivalent, key selection considerations include its 12-lead MSOP thermal performance (–40°C to 150°C), programmable soft-start via SS pin, spread-spectrum EMI reduction, and dual-mode light-load operation (pulse-skipping or low-ripple Burst Mode).

Technical Context

The LT8357HMSE#PBF implements fixed-frequency current-mode control with adjustable 100kHz–2MHz operation via RT resistor or external clock synchronization on SYNC/MODE pin. Its dual-gate driver (GATEP/GATEN) delivers independent 5V pull-up and pull-down paths to optimize MOSFET switching efficiency and EMI.

It integrates an internal 5V LDO (INTVCC) with 60mA current limit, accurate 1V FB reference (±1.5%), and fault protection including output overvoltage detection (±8% PGOOD thresholds), SENSE-based overcurrent latch, and frequency foldback below 75% FB regulation voltage to prevent minimum-on-time limitation during startup or short-circuit conditions.

Key Specifications

Pinout & Package

LT8357HMSE#PBF is housed in a thermally enhanced 12-lead MSOP package (MSE) with exposed GND pad (Pin 13). The exposed pad must be soldered directly to PCB ground plane for thermal management and EMI control.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar DC/DC controller applications.

Compared with LTC3789EMSE#PBF and MAX20096ATPA/VY+, the LT8357HMSE#PBF uniquely combines AEC-Q100 Grade H qualification, 3V–60V input range, triple-topology support (boost/SEPIC/flyback), and both Burst Mode and spread-spectrum EMI reduction - making it the only option qualified for under-hood battery monitoring with multi-year standby life.

Availability

LT8357HMSE#PBF is available at Aetrix Electronics and suitable for automotive powertrain monitoring, industrial 24V-to-48V conversion, and portable medical instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT8357HMSE#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 technologies, serving automotive, industrial, communications, and healthcare markets.

The LT8357HMSE#PBF belongs to Analog Devices' Power by Linear™ family of high-voltage DC/DC controllers, designed specifically for robust, low-EMI power conversion in harsh automotive and industrial environments.

FAQ

What is the maximum junction temperature rating for the LT8357HMSE#PBF?

The LT8357HMSE#PBF is rated for operation from –40°C to +150°C junction temperature and is AEC-Q100 Grade H qualified. This specification is validated per automotive reliability standards and confirmed in the Absolute Maximum Ratings table. Thermal derating begins above 125°C, and continuous operation above 150°C may impair device lifetime. The exposed pad (Pin 13) must be soldered to PCB ground to achieve the specified θJA of 40°C/W.

Does the LT8357HMSE#PBF support flyback topology with primary-side sensing?

Yes, the LT8357HMSE#PBF supports flyback configuration using primary-side sensing. Its current-mode architecture and SENSE pin interface allow direct sensing of primary current via a resistor in the MOSFET source path. The datasheet includes flyback design equations and a typical application circuit (Figure TA01a) confirming this capability. No optocoupler or secondary-side feedback is required for basic regulation, though FB can be used for tighter output accuracy if secondary sensing is added.

How does the LT8357HMSE#PBF implement spread-spectrum frequency modulation?

The LT8357HMSE#PBF implements triangle spread-spectrum modulation by varying the oscillator frequency ±9.5% around the nominal value (19% total spread), activated when SYNC/MODE is tied to INTVCC or pulled to GND via 100kΩ. This modulation reduces peak conducted EMI amplitude without altering average switching frequency or control loop behavior. Measured EMI reductions are shown in Figures F02 and F03 of the datasheet, demonstrating compliance advantages in noise-sensitive automotive and industrial systems.

Can the LT8357HMSE#PBF be synchronized to an external clock while operating in Burst Mode?

No - the LT8357HMSE#PBF disables Burst Mode operation when external clock synchronization is active. According to the Pin Functions section, "When synchronizing to an external clock, the LT8357 will forbid entering Burst Mode operation at light load conditions, but instead operate in the pulse-skipping mode." This restriction ensures deterministic timing alignment with the external clock source. To retain Burst Mode, SYNC/MODE must be configured for internal oscillator operation (e.g., floating or tied to GND with 100kΩ).

What is the purpose of the 55Ω internal pull-down on the SS pin during fault conditions?

The 55Ω internal pull-down on the SS pin forces rapid discharge during overcurrent faults, resetting the latched fault condition. As described in the Start-Up and Fault Protection section, when SENSE detects overcurrent, the SS pin is discharged by a 1.5µA pull-down current until voltage falls below 0.2V, at which point the fault flag resets and soft-start reinitiates. The 55Ω path ensures immediate hard pull-down during initial POR and fault recovery, guaranteeing reliable reset timing independent of external capacitor value - a critical safety feature for automotive applications.