Monolithic Power Systems Inc. NB679GD-P

Overview

NB679GD-P from Monolithic Power Systems is a fully integrated synchronous buck converter with fixed 5 V output, delivering up to 8 A continuous and 10 A peak current from a 5.5–24 V input. It integrates adaptive constant-on-time (COT) control, DC auto-tune loop, and a built-in 5 V/100 mA LDO with switch-over capability. Designed for high-efficiency power delivery in space-constrained computing systems, it operates at 700 kHz with ultrasonic mode support and features OCP, OVP, UVP, and thermal shutdown.

For engineers reviewing the NB679GD-P datasheet, NB679GD-P pinout, NB679GD-P application, or NB679GD-P equivalent, key selection criteria include its QFN-12 (2 mm × 3 mm) package, 1% output voltage accuracy, 100 µA quiescent current in shutdown, and dual enable control (EN/ENLDO) enabling independent buck and LDO sequencing in portable power architectures.

Technical Context

The NB679GD-P employs adaptive COT control with internal one-shot timing to maintain stable 700 kHz switching across input and load variations, while its DC auto-tune loop dynamically adjusts the reference to achieve ±0.5% load regulation without external compensation. The architecture integrates high-side and low-side MOSFETs with 25 mΩ and 12 mΩ R_DS(on), respectively, enabling high efficiency from 100 mA to full 8 A load.

It supports two operational modes: normal PWM mode above critical current (~3.5 A at 12 V_IN), and ultrasonic mode (USM) when EN is biased between 1.4–1.8 V-suppressing audible noise during light-load conditions by dynamically extending off-time and reducing switching frequency below 25 kHz only when necessary.

Key Specifications

Pinout & Package

The NB679GD-P is housed in a thermally enhanced QFN-12 package (2 mm × 3 mm, 0.5 mm pitch) with an exposed thermal pad (PGND-connected) for efficient heat dissipation in high-current applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2315DJ-LF-Z and RT7295BGJ8F, the NB679GD-P uniquely combines fixed 5 V regulation, ultrasonic mode, and a switch-over LDO in a single QFN-12 package-making it optimal for space- and noise-constrained portable computing where auxiliary rail integration reduces component count and improves standby efficiency.

Availability

NB679GD-P is available at Aetrix Electronics and suitable for laptop mainboard power, tablet SoC rail, network-attached storage (NAS) boards, and flat panel display logic supply requiring stable component supply, consistent parametric performance, and long-term lifecycle support.

Supply support for NB679GD-P 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

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and power ICs, with design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The NB679GD-P belongs to MPS's NB-series high-current buck converters, engineered specifically for compact, high-efficiency DC/DC conversion in portable computing and consumer electronics where thermal density, acoustic performance, and integration are critical.

FAQ

What is the minimum input voltage required for the NB679GD-P to start switching?

The NB679GD-P has an input UVLO rising threshold of 4.45–4.7 V. It begins switching only when VIN exceeds this range; hysteresis of 450 mV ensures stable turn-on without oscillation near the threshold. Below 4.45 V, the device remains in shutdown with <2 µA quiescent current.

Can the NB679GD-P operate with only ceramic output capacitors?

Yes-the NB679GD-P's adaptive COT control and internal compensation are explicitly designed for stability with ceramic output capacitors. The datasheet confirms stable operation with ≥22 µF X7R/X5R ceramics and specifies ESR-independent loop behavior, eliminating need for tantalum or polymer alternatives.

How does the LDO switch-over function work, and when does it activate?

The LDO switches from VIN-derived to VOUT-derived supply when VOUT reaches ≥4.8 V and the PG signal asserts high. This transition reduces dropout loss and improves LDO efficiency by ~15% at 50 mA load. It is automatic and requires no external control signals or configuration.

What is the purpose of the NC pin (Pin 4), and how should it be handled on the PCB?

Pin 4 is an unconnected (NC) die pad with no internal bond wire. It must remain electrically isolated-no trace, solder mask opening, or thermal relief should connect to it. Leaving it floating prevents parasitic coupling into sensitive analog nodes like AGND or VOUT, preserving regulation accuracy and noise immunity.

Does the NB679GD-P support external synchronization of its switching frequency?

No-the NB679GD-P uses fixed-frequency adaptive COT control with no SYNC pin or external clock input. Its 700 kHz nominal frequency varies slightly with input/output conditions but is not programmable or synchronizable. For sync-capable alternatives, consider MPS's MPQ4470 or Richtek's RT7295B.

How is thermal shutdown triggered, and what happens after it activates?

Thermal shutdown activates when junction temperature exceeds 140°C (typical), turning off both high- and low-side MOSFETs and asserting PG low. After cooldown to ~115°C (25°C hysteresis), the device reinitiates soft-start-ramping VOUT from zero-without requiring EN toggle or power cycle, enabling autonomous recovery in thermally intermittent environments.

Is the NB679GD-P RoHS-compliant and lead-free?

Yes-the NB679GD-P is fully RoHS-compliant, lead-free, and halogen-free per MPS's green status documentation. It meets JEDEC J-STD-020 moisture sensitivity level 3 (MSL-3) and is qualified for reflow soldering per IPC/JEDEC J-STD-020 standards.