Analog Devices Inc. LTC7851EUHH-1#TRPBF

Overview

LTC7851EUHH-1#TRPBF from Analog Devices is a quad-output, multiphase synchronous step-down voltage mode DC/DC controller optimized for DrMOS power stages. It delivers precise current sharing across up to four phases, supports 250kHz–2.25MHz switching frequency, operates with 3V–5.5V VCC and 3V–27V VIN, and regulates outputs from 0.6V to VCC – 0.5V - enabling high-current FPGA/DSP core supplies such as 1V/90A and 1.5V/30A.

For engineers reviewing the LTC7851EUHH-1#TRPBF datasheet, LTC7851EUHH-1#TRPBF pinout, LTC7851EUHH-1#TRPBF application, or LTC7851EUHH-1#TRPBF equivalent, key selection criteria include its lower-current-sense-amplifier-gain architecture (4 V/V), compatibility with integrated DrMOS current sensing, 58-lead 5mm × 9mm QFN package, and phase-lockable fixed-frequency operation with ±0.75% 0.6V reference accuracy.

Technical Context

The LTC7851EUHH-1#TRPBF implements voltage-mode control with independent error amplifiers per channel and a dedicated internal current sharing loop using IAVG bus averaging. Its differential output voltage sense amplifiers (VSNSP/VSNSN) enable remote sensing with offset cancellation, while lossless DCR or precision resistor-based current sensing feeds into a 4 V/V gain current sense amplifier - specifically tuned for DrMOS devices with internal current sense signals.

It features a programmable oscillator (250kHz–2.25MHz via FREQ pin or external CLKIN), four independent RUN pins for per-channel enable/disable, soft-start/tracking capability on each channel (TRACK/SSx), and open-drain PGOOD outputs with 30µs delay. The device supports master/slave multiphase configurations via VSNSOUT and IAVG pin interconnection, and includes line feedforward compensation via VINSNS.

Key Specifications

Pinout & Package

Package: 58-lead plastic QFN (5mm × 9mm, 0.4mm pitch), exposed thermal pad (Pin 59) soldered to SGND for thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC7851EUHH#TRPBF and MP2960AQS-LF-Z, the LTC7851EUHH-1#TRPBF offers superior analog current sharing fidelity for DrMOS-based high-current rails, simpler analog loop compensation due to true op-amp COMP outputs, and greater frequency agility - making it preferred for performance-critical, analog-controlled server and telecom VRMs where digital overhead is unnecessary.

Availability

LTC7851EUHH-1#TRPBF is available at Aetrix Electronics and suitable for high-current distributed power systems, FPGA/ASIC core supplies, and datacom/telecom board-level power requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for LTC7851EUHH-1#TRPBF 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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and aerospace markets.

The LTC7851 product line is designed for high-efficiency, high-current, multiphase synchronous buck conversion in computing, networking, and FPGA power delivery - emphasizing precision current sharing, wide frequency agility, and robust analog control architecture.

FAQ

What is the key functional difference between LTC7851EUHH-1#TRPBF and LTC7851EUHH#TRPBF?

The LTC7851EUHH-1#TRPBF features a reduced current sense amplifier gain of 4 V/V and a higher maximum differential input voltage of 150mV, making it specifically optimized for DrMOS devices with integrated current sense outputs. In contrast, the standard LTC7851EUHH#TRPBF uses 20 V/V gain and 50mV full-scale range, intended for discrete sense resistors or low-gain power blocks. This difference ensures proper signal scaling and avoids saturation when interfacing with DrMOS current sense pins.

Can LTC7851EUHH-1#TRPBF operate as four independent single-phase controllers?

Yes, the LTC7851EUHH-1#TRPBF can operate as four independent single-phase controllers. Each channel has dedicated RUN, TRACK/SS, FB, COMP, PWM, and PGOOD pins, allowing fully autonomous configuration. Independent soft-start timing, output voltage setting, and enable control are supported - verified in the datasheet's "Single Phase Using FDMF5820DC DrMOS" test circuits and startup waveforms (Figures G10–G13).

What is the recommended layout practice for the exposed thermal pad (Pin 59) on LTC7851EUHH-1#TRPBF?

The exposed thermal pad (Pin 59) of the LTC7851EUHH-1#TRPBF must be soldered to a solid SGND plane on the PCB using an array of thermal vias (minimum 9 vias, 0.3mm diameter) to achieve the rated θJC = 15.5°C/W and θJA = 49°C/W. The datasheet explicitly states "EXPOSED PAD (PIN 59) IS SGND, MUST BE SOLDERED TO PCB", and thermal performance degrades significantly if left unconnected or improperly thermally coupled.

How does the LTC7851EUHH-1#TRPBF implement current sharing in multiphase operation?

The LTC7851EUHH-1#TRPBF implements current sharing via its IAVG bus: the master channel's current sense amplifier output is averaged onto the IAVG pin (with 100pF typical capacitor), and all slave channels connect their IAVG pins to this node. Each slave integrates the difference between its sensed current and the master's average, then sums that error with its COMP voltage to adjust duty cycle - achieving <±3% current matching across phases as confirmed in Figure 1 and the Applications Information section.

Does LTC7851EUHH-1#TRPBF support external clock synchronization, and what is the valid frequency range?

Yes, the LTC7851EUHH-1#TRPBF supports external clock synchronization via the CLKIN pin (Pin 55), which accepts a clean CMOS/TTL clock signal from 250kHz to 2.25MHz. The rising edge of CLKIN aligns with the rising edge of PWM1 in closed-loop operation. Internal pull-up ensures reliable operation when CLKIN is floating, and the device maintains phase coherence across all four PWM outputs when synchronized - as detailed in the Oscillator and PLL electrical characteristics table and Pin Functions section.