Analog Devices Inc. LTC3618IFE#TRPBF

Overview

LTC3618IFE#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel synchronous buck converter IC designed specifically for DDR memory power delivery, providing ±3A VDDQ and matched ±3A VTT outputs with 0.5% VDDQ reference accuracy and programmable 4MHz switching. It integrates VTTR buffering (VDDQIN/2), phase-shift control (0°/90°/180°), and supports DDR, DDR2, and DDR3 termination standards in high-density memory subsystems.

For engineers reviewing the LTC3618IFE#TRPBF datasheet, LTC3618IFE#TRPBF pinout, LTC3618IFE#TRPBF application, or LTC3618IFE#TRPBF equivalent, key selection criteria include dual ±3A current capability per channel, ±1% output voltage accuracy over temperature, 2.25V–5.5V input range, 4MHz max switching frequency with external RT resistor, and selectable forced continuous or pulse-skipping mode for VDDQ - all critical for low-noise, high-efficiency DDR supply design.

Technical Context

The LTC3618IFE#TRPBF implements a current-mode, constant-frequency architecture with independent control loops for VDDQ and VTT channels. VDDQ uses an internal 0.6V reference with ±1% accuracy, while VTT regulates to VTTR (VDDQIN/2) with ±6mV tracking error, enabling precise DDR termination matching. Both channels support internal or external compensation and feature dedicated ITH pins for loop stability tuning.

Phase shift between SW1 and SW2 is digitally selected via the PHASE pin (0° at SGND, 90° at mid-rail, 180° at SVIN), reducing input ripple by up to 70% in antiphase configuration. The MODE/SYNC pin enables either pulse-skipping (for light-load efficiency) or forced continuous mode (required for bidirectional VTT sinking), with VTT permanently in forced continuous mode for stable termination under dynamic load reversal.

Key Specifications

Pinout & Package

The LTC3618IFE#TRPBF is packaged in a thermally enhanced 24-pin TSSOP (FE package) with exposed PGND pad (Pin 25), rated for θ_JA = 33°C/W. Pin assignment is identical between FE and UF packages, with dual-source pins (e.g., PVIN1 ×2, SW1 ×2) for low-impedance power routing.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-output DDR buck converter applications.

Compared with TPS51216RUKT and ISL95831IRZ, the LTC3618IFE#TRPBF uniquely integrates a buffered VTTR output, supports 4MHz switching for ultra-compact magnetics, and provides hardware-selectable phase shift - making it optimal for space-constrained, high-performance DDR3/DDR4 systems demanding analog precision and minimal external components.

Availability

LTC3618IFE#TRPBF is available at Aetrix Electronics and suitable for DDR memory subsystems, server DIMM modules, and industrial PLC interfaces requiring stable component supply, long-term lifecycle assurance, and guaranteed performance across –40°C to 125°C.

Supply support for LTC3618IFE#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and computing markets.

The LTC3618IFE#TRPBF belongs to Linear's Power by Linear™ family of high-efficiency DC/DC converters, engineered specifically for DDR memory power integrity - emphasizing tight tracking, low noise, and robust transient response in memory-intensive applications.

FAQ

What is the maximum supported switching frequency for LTC3618IFE#TRPBF?

The LTC3618IFE#TRPBF supports up to 4MHz switching frequency, set via an external resistor on the RT pin. At 4MHz, minimum on-time (80ns) limits practical duty cycle to ≥32% at 5.5V input. For reliable operation above 3MHz, use low-ESR ceramic capacitors and shielded 0.47µH–1.0µH inductors to manage gate charge losses and EMI.

Does LTC3618IFE#TRPBF support bidirectional current on the VTT output?

Yes, the LTC3618IFE#TRPBF VTT channel delivers ±3A continuously and is always in forced continuous mode - essential for DDR termination that sources current during reads and sinks current during writes. This is confirmed in the datasheet's Electrical Characteristics table (ILIMX negative limit = –3.5A) and Applications Information section.

How is VTTR generated and what is its load capability in LTC3618IFE#TRPBF?

The LTC3618IFE#TRPBF generates VTTR as a buffered, high-accuracy copy of VDDQIN/2 using an internal op-amp. It delivers ±10mA with ±1% line/load regulation and must be loaded with ≤0.1µF capacitance. Exceeding this capacitance risks instability, as noted in the Pin Functions description for Pin 14 (VTTR).

Can LTC3618IFE#TRPBF operate with different input voltages on PVIN1 and PVIN2?

Yes, the LTC3618IFE#TRPBF supports independent PVIN1 and PVIN2 supplies - each can be connected to equal or lower voltages than SVIN, enabling flexible power tree design. The Absolute Maximum Ratings specify PVIN1/PVIN2 up to 6V, and the Pin Functions section confirms they are "independent of each other" for optimized thermal distribution.

What is the purpose of the PHASE pin on LTC3618IFE#TRPBF and how is it configured?

The PHASE pin (Pin 1) selects inter-channel phase offset: 0° (tie to SGND), 90° (bias to SVIN/2), or 180° (tie to SVIN). This reduces input capacitor RMS current and EMI - antiphase (180°) cuts ripple by ~70% versus in-phase operation. Configuration is verified in the Pin Functions section and Typical Application schematic (TA01a).