Texas Instruments LP2997MR/NOPB

Overview

LP2997MR/NOPB 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 - deployed in high-speed memory subsystems for server motherboards and embedded computing platforms.

For engineers reviewing the LP2997MR/NOPB datasheet, LP2997MR/NOPB pinout, LP2997MR/NOPB application, or LP2997MR/NOPB equivalent, key selection considerations include its SO PowerPAD-8 thermal performance (θJA = 43°C/W), active-low shutdown for Suspend-to-RAM, dual-rail architecture (AVIN/PVIN separation), and precise VTT tracking under dynamic DDR-II bus loads.

Technical Context

The LP2997MR/NOPB implements a linear topology with separate analog (AVIN) and power (PVIN) supply rails to minimize internal dissipation and improve noise isolation. Its output stage prevents shoot-through while supporting bidirectional current flow up to ±900 mA peak.

It uses an internal 50 kΩ resistor divider on VDDQ to generate VREF = VDDQ/2, which feeds a high-gain error amplifier controlling VTT. The VSENSE pin enables remote sensing at the midpoint of the termination bus, correcting IR drop across long PCB traces.

Key Specifications

Pinout & Package

LP2997MR/NOPB is housed in an 8-pin SO PowerPAD package (Package Code DDA), featuring an exposed thermal pad (EP) connected to GND for enhanced heat dissipation (θJA = 43°C/W). This thermally optimized variant replaces the standard SOIC-8 (θJA = 151°C/W) in high-current applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS51100DGQR and LM1085IT-ADJ/NOPB, LP2997MR/NOPB uniquely integrates VDDQ-synchronized VREF, VSENSE-based remote regulation, and STR-ready shutdown - making it the only solution qualified for JEDEC-compliant DDR-II termination without external components or layout compromises.

Availability

LP2997MR/NOPB is available at Aetrix Electronics and suitable for DDR-II memory termination, SSTL-18 interface design, and industrial embedded memory subsystems requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for LP2997MR/NOPB 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 power management ICs, with decades of DDR interface expertise and JEDEC-compliant product validation.

The LP2997MR/NOPB belongs to TI's DDR termination regulator product line, engineered specifically to replace discrete resistor networks and op-amp-based solutions in JEDEC SSTL-18 memory systems - emphasizing precision, thermal resilience, and system-level power management.

FAQ

What is the primary function of LP2997MR/NOPB in a DDR-II memory system?

The LP2997MR/NOPB serves as a dedicated linear termination regulator that generates and maintains the VTT voltage at exactly VDDQ/2 (e.g., 0.9 V when VDDQ = 1.8 V) for DDR-II SSTL-18 interfaces. It actively sources and sinks current to counteract bus switching transients while delivering ±500 mA continuous output. Its integrated VREF buffer and VSENSE pin ensure accurate, stable termination across distributed memory topologies - a core requirement validated per JEDEC standards.

How does the SO PowerPAD-8 package of LP2997MR/NOPB improve thermal performance over SOIC-8 variants?

The LP2997MR/NOPB's SO PowerPAD-8 package features an exposed thermal pad (EP) electrically tied to GND and designed for direct soldering to a large PCB copper area. This configuration achieves θJA = 43°C/W - more than 3× better than the SOIC-8 version (θJA = 151°C/W). As a result, LP2997MR/NOPB sustains full ±500 mA load at 85°C ambient without thermal derating, whereas the SOIC-8 variant would require significant airflow or heatsinking to avoid shutdown.

Can LP2997MR/NOPB operate with VDDQ = 1.5 V or 2.5 V, or is it limited to 1.8 V?

LP2997MR/NOPB supports VDDQ from 1.7 V to 1.9 V per Electrical Characteristics tables, with nominal operation at 1.8 V. While VDDQ = 1.5 V falls outside the specified range and risks violating VTT regulation accuracy (VTT = VDDQ/2 ≈ 0.75 V, below SSTL-18 spec), VDDQ = 2.5 V exceeds the absolute maximum rating (VDDQ ≤ 6 V but must satisfy VDDQ < 2 × (AVIN − 1)). For SSTL-18 compliance, LP2997MR/NOPB must be used with VDDQ = 1.8 V - confirmed by JEDEC test conditions and TI's recommended application circuits.

What happens to VREF and VTT when the SD pin is asserted low on LP2997MR/NOPB?

When SD is pulled low, LP2997MR/NOPB enters Suspend-to-RAM (STR) mode: VTT is tri-stated (high-impedance), disconnecting it from the termination bus to eliminate leakage paths and reduce system standby power, while VREF remains fully active and regulated at VDDQ/2. This preserves the reference voltage for memory and chipset during low-power states. Quiescent current drops to 115–150 µA, and thermal shutdown remains functional - ensuring safe operation if junction temperature exceeds 165°C.

Is external compensation required for LP2997MR/NOPB stability, and what capacitor values are recommended?

No external compensation is required for LP2997MR/NOPB - its internal error amplifier is unity-gain stable across all recommended output capacitors. TI specifies minimum 100 µF bulk capacitance at VTT with low ESR (<20 mΩ), plus local 0.1 µF ceramic bypass at AVIN and VREF. For VSENSE, a 0.1 µF ceramic capacitor placed adjacent to the pin suppresses high-frequency noise. Input capacitor at PVIN (10–22 µF) improves transient response but is not mandatory for stability.