Texas Instruments LP2997M-TI

Overview

LP2997M-TI from Texas Instruments is a linear DDR-II termination regulator designed to meet JEDEC SSTL-18 specifications. It delivers ±500 mA continuous sourcing/sinking current, regulates VTT to precisely VDDQ/2 (e.g., 0.9 V at VDDQ = 1.8 V), and features integrated VREF buffer and VSENSE for remote load regulation-used in high-speed memory subsystems for server and workstation motherboards.

For engineers reviewing the LP2997M-TI datasheet, LP2997M-TI pinout, LP2997M-TI application, or LP2997M-TI equivalent, key selection criteria include VTT output accuracy under transient load, thermal performance in SOIC-8 vs. PowerPAD-8 packages, STR functionality via active-low SD pin, and dual-rail input architecture (AVIN/PVIN) for optimized power dissipation.

Technical Context

The LP2997M-TI implements a linear topology with separate analog (AVIN) and power (PVIN) supply rails to isolate control circuitry from the high-current output stage. Its internal 50 kΩ resistor divider generates VREF = VDDQ/2, enabling precise tracking of memory rail voltage.

VSENSE enables remote sensing at the bus midpoint to compensate for IR drop across long VTT planes, while the active-low SD pin tri-states VTT but maintains VREF during Suspend-to-RAM-supporting low-quiescent-current operation (115–150 µA in shutdown) without losing reference stability.

Key Specifications

Pinout & Package

LP2997M-TI is available in SOIC-8 (Package Drawing D) and SO PowerPAD-8 (Package Drawing DDA), both 8-pin surface-mount packages with exposed thermal pad (DDA only). The SOIC-8 variant uses standard gull-wing leads; PowerPAD-8 adds bottom-side copper pad for enhanced thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar DDR-II termination regulator applications.

Compared with TPS51100PWR and LM1085IT-ADJ, LP2997M-TI uniquely integrates VREF buffer, VSENSE, and STR functionality in a single SOIC-8 package-eliminating design complexity, reducing BOM count, and guaranteeing JEDEC-compliant termination without trade-offs in noise or transient performance.

Availability

LP2997M-TI is available at Aetrix Electronics and suitable for DDR-II memory termination, SSTL-18 interface design, and Suspend-to-RAM power management requiring stable component supply across industrial, computing, and communications platforms.

Supply support for LP2997M-TI 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and high-reliability solutions for industrial, automotive, and computing markets.

The LP2997M-TI belongs to TI's DDR memory interface power portfolio, engineered specifically to replace discrete termination networks with a single-chip, JEDEC-compliant linear regulator for DDR-II systems.

FAQ

What is the primary function of the LP2997M-TI in a DDR-II memory system?

The LP2997M-TI serves as a dedicated linear termination regulator that supplies precise VTT = VDDQ/2 (e.g., 0.9 V) and a buffered VREF = VDDQ/2 reference to DDR-II SDRAM interfaces. It sources and sinks up to ±500 mA continuously to maintain signal integrity across SSTL-18 buses, while its VSENSE pin enables remote regulation to counteract IR drop on long PCB traces. This ensures JEDEC-compliant termination without external resistors or calibration.

How does the SD pin on the LP2997M-TI support Suspend-to-RAM functionality?

When the SD pin of the LP2997M-TI is pulled low, the VTT output enters high-impedance (tri-state) mode, halting current flow to termination resistors and reducing system power. Crucially, the VREF output remains active-providing uninterrupted reference voltage to the memory controller and DIMMs. Quiescent current drops to 115–150 µA, enabling low-power STR states without compromising memory state retention or requiring reinitialization upon wake-up.

Can the LP2997M-TI operate with different VDDQ voltages, and how does it affect VTT accuracy?

Yes-the LP2997M-TI dynamically tracks VDDQ via an internal 50 kΩ resistor divider, so VTT = VDDQ/2 across its specified range (1.7–1.9 V). At VDDQ = 1.7 V, VTT = 0.856 V (typ); at 1.8 V, VTT = 0.908 V (typ); at 1.9 V, VTT = 0.957 V (typ). Electrical Characteristics confirm ±25 mV offset over temperature and load, ensuring consistent SSTL-18 compliance regardless of VDDQ variation-critical for systems with adaptive memory voltage scaling.

What is the role of the VSENSE pin on the LP2997M-TI, and how should it be implemented?

The VSENSE pin on the LP2997M-TI provides remote feedback for improved load regulation. It should be connected to the midpoint of the VTT termination plane-not at the regulator output-to compensate for IR drop across long PCB traces. For optimal performance, route VSENSE with minimal length, avoid proximity to noisy signals, and place a 0.1 µF ceramic capacitor near the pin. If remote sensing isn't used, VSENSE must still be tied directly to VTT to ensure stable regulation.

Which package options are available for the LP2997M-TI, and how do they differ thermally?

The LP2997M-TI is offered in SOIC-8 (Package D) and SO PowerPAD-8 (Package DDA). The SOIC-8 has θJA = 151 °C/W on a standard JEDEC board, limiting continuous ±500 mA operation above ~60°C ambient. The PowerPAD-8 variant integrates an exposed thermal pad connected to GND, achieving θJA = 43 °C/W-enabling full-rated output at 85°C ambient. Both packages are RoHS-compliant and pin-compatible; thermal design dictates selection based on airflow, copper area, and vias.