Analog Devices Inc. LTC1705EGN

Overview

LTC1705EGN from Analog Devices (formerly Linear Technology) is a dual synchronous buck controller with integrated 5-bit VID DAC and 150mA LDO, designed specifically for Intel Mobile Pentium processor core, I/O, and CLK power supplies. It delivers 15A core output at 0.9V–2.0V, 3A I/O at 1.5V, and 150mA CLK at 2.5V using all-N-channel MOSFETs, 550kHz PWM, and voltage-mode feedback.

For engineers reviewing the LTC1705EGN datasheet, LTC1705EGN pinout, LTC1705EGN application, or LTC1705EGN equivalent, key selection considerations include Intel Mobile VID compliance, out-of-phase switching to minimize input ripple, ±1.25% core DC accuracy, PGOOD monitoring of all three outputs, and thermal shutdown at 155°C.

Technical Context

The LTC1705EGN implements two independent voltage-mode synchronous buck controllers-one for core (15A) and one for I/O (3A)-each driving external N-channel MOSFET pairs via floating top-gate drivers (TGC/TGIO) and bottom-gate drivers (BGC/BGIO). It uses a constant-frequency 550kHz oscillator with 180° phase shift between channels to reduce input capacitor RMS current.

Core output voltage is set by an internal 5-bit VID DAC compliant with Intel Mobile VRM specifications (0.9V–2.0V in 50mV steps), while the CLK supply employs an integrated P-channel LDO delivering 2.5V ±0.05V at up to 150mA. Feedback loops feature 20MHz gain-bandwidth error amplifiers and no external current-sense resistors-current limiting is achieved via V_DS sensing across the bottom MOSFETs.

Key Specifications

Pinout & Package

Package: 28-pin narrow SSOP (GN), 5.6mm × 10.2mm, 0.635mm pitch, RoHS-compliant plastic body with exposed thermal pad (not electrically connected).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-buck controller with VID and LDO applications.

Compared with ISL6225CRZ and TPS51020PWR, the LTC1705EGN uniquely integrates all three regulated rails-core, I/O, and 2.5V CLK-in one SSOP package with Intel Mobile VID compliance, eliminating external LDOs and simplifying power tree validation for legacy Pentium platforms.

Availability

LTC1705EGN is available at Aetrix Electronics and suitable for notebook PC motherboard design, Intel Mobile Pentium platform power delivery, and embedded computing systems requiring stable, multi-rail power supply solutions.

Supply support for LTC1705EGN 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; Linear originally developed the LTC1705 as part of its high-performance power management portfolio for computing applications.

The LTC1705 belongs to Linear's dedicated microprocessor power controller product line, engineered to meet Intel VRM specifications with integrated VID decoding, synchronous rectification, and multi-rail coordination for mobile CPU platforms.

FAQ

What is the maximum output current supported by the LTC1705EGN core regulator?

The LTC1705EGN core regulator supports up to 15A output current, as confirmed by the typical application circuit (TA01) showing 15A load with 0.68µH inductor and six 180µF output capacitors. This rating assumes proper thermal management, appropriate external MOSFET selection (e.g., FDS6670A), and adherence to the IMAXC current limit programming guidelines in the datasheet.

Does the LTC1705EGN require external current-sense resistors for overcurrent protection?

No, the LTC1705EGN does not require external current-sense resistors. It implements MOSFET V_DS-based current limiting for both core and I/O channels-monitoring the voltage drop across the bottom N-channel MOSFET (QBC/QBIO) to trigger current limit. This architecture eliminates power loss and layout sensitivity associated with shunt resistors, improving efficiency and reliability in the LTC1705EGN design.

How does the LTC1705EGN implement VID voltage programming for Intel Mobile Pentium processors?

The LTC1705EGN implements VID programming via five dedicated inputs (VID4–VID0) that connect to an internal resistor network tied to FBC and SENSEC. The 5-bit code selects one of 32 output voltages from 0.90V to 2.00V in 50mV steps, fully compliant with Intel Mobile VRM specifications. Each VID pin includes a 30kΩ internal pull-up, allowing direct connection to CPU VID lines without external biasing-ensuring correct LTC1705EGN core voltage setup.

What is the purpose of the RUN/SS pin on the LTC1705EGN, and how is it used?

The RUN/SS pin on the LTC1705EGN serves dual functions: hard shutdown when pulled to GND (reducing supply current to <100µA), and soft-start control when biased with a capacitor to GND. An internal 3µA current source charges the capacitor, setting the turn-on ramp time at ~300ms/µF-enabling controlled voltage rise on core and I/O outputs. This prevents inrush current and ensures proper power sequencing in the LTC1705EGN application.

Can the LTC1705EGN's CLK output (VOUTCLK) be used for non-Intel processors requiring a 2.5V supply?

Yes, the LTC1705EGN's VOUTCLK pin delivers a regulated 2.5V ±0.05V output capable of sourcing up to 150mA, making it suitable for any 2.5V logic or clock rail-not exclusively Intel processors. Its integrated LDO, short-circuit protection, and thermal shutdown provide robust operation independent of the core/I/O controllers, allowing flexible reuse in FPGA I/O banks, DDR2 termination, or other 2.5V subsystems alongside the LTC1705EGN.