Texas Instruments LP2995LQ/NOPB

Overview

LP2995LQ/NOPB from Texas Instruments is a linear DDR termination regulator designed for SSTL-2 and SSTL-3 bus termination in DDR-SDRAM systems. It sources and sinks up to ±3A transient current while regulating VTT to precisely VDDQ/2 (e.g., 1.25V at VDDQ = 2.5V), features integrated VREF buffered reference output, and operates with AVIN/PVIN supply range of 2.2V–5.5V.

For engineers reviewing the LP2995LQ/NOPB datasheet, LP2995LQ/NOPB pinout, LP2995LQ/NOPB application, or LP2995LQ/NOPB equivalent, key selection criteria include VTT load regulation accuracy (±15 mV offset), dual-rail input architecture (AVIN/PVIN), remote sense capability via VSENSE, thermal performance in WQFN-16 (θJA = 51°C/W), and JEDEC-compliant SSTL-2/SSTL-3 termination support.

Technical Context

The LP2995LQ/NOPB implements a high-speed linear topology with separate analog (AVIN) and power (PVIN) supply rails to isolate control circuitry from output stage noise. Its internal 50kΩ resistor divider sets VREF and VTT to track VDDQ/2, enabling precise 1.25V termination for SSTL-2 or scalable reference for SSTL-3 via external resistor networks.

VSENSE enables remote load regulation by sensing voltage at the bus midpoint, compensating for IR drop across long PCB traces. The output stage prevents shoot-through during bidirectional current transitions, supporting fast transient response to ±3A load steps required by DDR memory data strobes and command/address lines.

Key Specifications

Pinout & Package

LP2995LQ/NOPB uses a 16-pin WQFN (NHP) package with exposed thermal pad (EP), measuring 4.0 mm × 4.0 mm × 0.8 mm. The package supports high-current thermal dissipation via soldered EP connection to PCB ground plane.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS51100DGQR, LP2995LQ/NOPB offers simpler layout and inherent noise immunity but lower efficiency; versus LP2996LQ/NOPB, it lacks enable control yet provides identical termination performance at lower cost for fixed-on applications.

Availability

LP2995LQ/NOPB is available at Aetrix Electronics and suitable for DDR-SDRAM termination, SSTL-2 interface design, and memory subsystem power delivery requiring stable component supply and JEDEC-compliant voltage accuracy.

Supply support for LP2995LQ/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 company specializing in analog, embedded processing, and logic technologies with over 50 years of leadership in power management ICs.

The LP2995LQ/NOPB belongs to TI's DDR termination regulator product line, engineered specifically to replace discrete op-amp + MOSFET solutions in JEDEC-compliant memory interfaces with integrated, low-noise linear regulation.

FAQ

What is the primary function of LP2995LQ/NOPB in a DDR-SDRAM system?

The LP2995LQ/NOPB serves as a dedicated linear termination regulator that generates and maintains the VTT termination voltage equal to VDDQ/2 (e.g., 1.25V) while also providing a buffered VREF reference. It sources and sinks bidirectional current up to ±3A to stabilize DDR bus signals, directly meeting JEDEC SSTL-2 and SSTL-3 specifications without external active components. This functionality is central to the LP2995LQ/NOPB's role in preventing signal reflections and ensuring timing margin in high-speed memory interfaces.

How does the VSENSE pin improve performance of LP2995LQ/NOPB in real-world layouts?

The VSENSE pin enables remote load regulation by allowing feedback sampling at the midpoint of the VTT distribution plane rather than at the LP2995LQ/NOPB output. This compensates for IR voltage drop across PCB traces, ensuring consistent 1.25V termination across all DDR devices-even on large motherboards with multi-inch VTT runs. If unused, VSENSE must still be tied to VTT per datasheet requirement. This feature directly enhances the LP2995LQ/NOPB's ability to meet tight ±15 mV VTT tolerance under dynamic loading conditions.

Can LP2995LQ/NOPB be used for SSTL-3 applications, and how is scaling adjusted?

Yes, LP2995LQ/NOPB supports SSTL-3 by modifying the internal reference scaling factor from VDDQ/2 to VDDQ×0.45 using an external 11.1kΩ resistor in series with the VDDQ pin. This alters the effective resistor divider ratio, shifting VTT and VREF outputs accordingly while preserving regulation accuracy and transient response. The LP2995LQ/NOPB datasheet explicitly validates this configuration, making it a verified method to reuse the same device across both SSTL-2 and SSTL-3 memory standards without hardware redesign.

What thermal considerations apply to LP2995LQ/NOPB in WQFN-16 package?

LP2995LQ/NOPB in WQFN-16 has θJA = 51°C/W on a JEDEC 4-layer board with optimized vias under the exposed pad. At 1.5A continuous load with 2.5V input, power dissipation exceeds 1W-requiring careful thermal derating above 85°C ambient. Layout best practices include connecting the EP pad to a solid ground plane with ≥4 thermal vias (1.27 mm pitch), avoiding solder mask over the pad, and ensuring airflow >200 LFPM for sustained high-current operation. These measures prevent junction temperature from exceeding 125°C and ensure reliable LP2995LQ/NOPB performance in thermally dense memory subsystems.

Why does LP2995LQ/NOPB use separate AVIN and PVIN supply pins?

LP2995LQ/NOPB separates AVIN (analog supply) and PVIN (power supply) to isolate noise-sensitive control circuitry-including the error amplifier and VREF buffer-from high-current switching transients in the VTT output stage. AVIN powers internal op-amps and bias networks, while PVIN exclusively feeds the power transistor driving VTT. This architecture minimizes PSRR degradation and preserves VREF stability under heavy load, directly contributing to the LP2995LQ/NOPB's ±15 mV VTT offset specification and robust DDR signal integrity.