Analog Devices Inc. LTC3851AHMSE-1#PBF

Overview

LTC3851AHMSE-1#PBF from Analog Devices (formerly Linear Technology) is a high-performance synchronous step-down switching regulator controller driving dual N-channel MOSFETs in constant-frequency current-mode operation. It delivers ±1% output voltage accuracy over 0.8V–5.5V range, supports 4V–38V input, operates up to 750kHz, and features power-good monitoring, adjustable soft-start/tracking, and current foldback protection - used in telecom intermediate bus converters and industrial 12V/24V-to-3.3V/5V point-of-load regulation.

For engineers reviewing the LTC3851AHMSE-1#PBF datasheet, LTC3851AHMSE-1#PBF pinout, LTC3851AHMSE-1#PBF application, or LTC3851AHMSE-1#PBF equivalent, key selection criteria include its H-grade temperature rating (–40°C to 150°C), PGOOD replacement of ILIM vs. LTC3851A, OPTI-LOOP® compensation for wide ESR/COUT tolerance, phase-lockable frequency tuning via FREQ/PLLFLTR, and dual-mode light-load control (Burst Mode® or pulse-skipping).

Technical Context

The LTC3851AHMSE-1#PBF implements a constant-frequency current-mode control architecture with transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz), precision 0.8V reference (±1% over –40°C to 150°C), and integrated 5V INTVCC LDO (4.8V–5.2V, 50mA peak). Its PWM logic includes anti-shoot-through timing (30ns dead time), 99% max duty cycle for ultra-low dropout, and reverse-current detection to prevent inductor current reversal.

It supports three light-load operating modes selected via MODE/PLLIN: forced continuous conduction (tie to INTVCC), pulse-skipping (tie to GND), or Burst Mode® (50k–250kΩ pull-up to INTVCC). The PLL circuit accepts external clocks from 250kHz to 750kHz and uses an RC filter on FREQ/PLLFLTR for lock stability - distinct from the LTC3851-1 with improved jitter performance.

Key Specifications

Pinout & Package

Package: 16-lead plastic MSOP with exposed thermal pad (Pin 17 = GND), rated θJA = 40°C/W. Designed for high-power density layouts with low-inductance Kelvin grounding and mandatory soldering of exposed pad.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous step-down controller applications.

Compared with LTC3851AIMSE-1#PBF, the LTC3851AHMSE-1#PBF offers 25°C higher junction temperature capability and tighter current sense threshold for high-current designs; versus MP2918GQ-Z, it provides greater flexibility in power stage selection, synchronization, and fault monitoring - at the cost of discrete MOSFET layout complexity.

Availability

LTC3851AHMSE-1#PBF is available at Aetrix Electronics and suitable for telecom intermediate bus converters, automotive ADAS power supplies, and industrial PLC I/O modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LTC3851AHMSE-1#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) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving aerospace, automotive, industrial, and communications markets.

The LTC3851A family was designed as a high-efficiency, thermally robust synchronous buck controller platform for demanding point-of-load and intermediate bus applications - emphasizing precision regulation, flexible light-load operation, and ruggedized packaging for harsh environments.

FAQ

What is the maximum operating junction temperature for LTC3851AHMSE-1#PBF?

The LTC3851AHMSE-1#PBF is rated for –40°C to 150°C junction temperature (H-grade), verified per manufacturer specifications. This exceeds the 125°C limit of I-grade variants and enables use in under-hood automotive or high-ambient industrial settings where thermal derating is critical. The exposed pad (Pin 17) must be soldered to PCB copper for effective heat transfer.

How does LTC3851AHMSE-1#PBF differ from LTC3851AEMSE-1#PBF?

The LTC3851AHMSE-1#PBF replaces the ILIM pin of the base LTC3851A with PGOOD, and is qualified for –40°C to 150°C operation (H-grade), whereas LTC3851AEMSE-1#PBF is E-grade (0°C to 85°C). Both share identical pinout, package, and functional architecture - but the H-grade version guarantees performance across the full extended temperature range with tighter current sense threshold (35mV vs. 40mV).

Can LTC3851AHMSE-1#PBF synchronize to an external clock?

Yes - the MODE/PLLIN pin of LTC3851AHMSE-1#PBF accepts external clock signals from 250kHz to 750kHz to force forced continuous mode and synchronize the internal oscillator. An RC network on FREQ/PLLFLTR serves as the PLL loop filter. Synchronization eliminates beat frequencies in multi-rail systems and simplifies EMI filtering by aligning switching edges.

What current sensing methods does LTC3851AHMSE-1#PBF support?

The LTC3851AHMSE-1#PBF supports both RSENSE (shunt resistor) and DCR (inductor winding resistance) current sensing via dedicated SENSE+ and SENSE– pins. RSENSE offers highest accuracy for current limiting; DCR reduces power loss and BOM cost in high-current applications. Input bias current is ±1µA, enabling use with high-value DCR networks.

Does LTC3851AHMSE-1#PBF provide overvoltage protection?

Yes - LTC3851AHMSE-1#PBF includes hardware-based output overvoltage protection that disables the top gate (TG) and enables the bottom gate (BG) when VFB exceeds ±10% of the 0.8V reference. This acts independently of the control loop and responds within nanoseconds to prevent damage to downstream loads during transient or fault conditions.