Monolithic Power Systems Inc. NB670GQ-Z

Overview

NB670GQ-Z from Monolithic Power Systems is a fully integrated 5V–24V input, 3.3V fixed-output synchronous buck converter with integrated 3.3V/100mA LDO and 300kHz CLK output. It delivers 6A continuous / 9A peak output current in a QFN-16 (3mm×3mm) package, employs Constant-On-Time control for fast transient response, and includes OCP, OVP, UVP, thermal shutdown, and output discharge-targeting compact power rails in laptop and tablet mainboard designs.

For engineers reviewing the NB670GQ-Z datasheet, NB670GQ-Z pinout, NB670GQ-Z application, or NB670GQ-Z equivalent, key selection considerations include its dual-regulator architecture (buck + LDO), integrated charge-pump clock, COT-based loop stability with ceramic-capable compensation, and latch-off reset via EN or VIN power cycle-critical for embedded power sequencing and standby rail management.

Technical Context

The NB670GQ-Z integrates a high-side MOSFET (30mΩ R_DS(ON)) and low-side MOSFET (15mΩ R_DS(ON)) in a single QFN-16 package, operating at 500kHz nominal switching frequency with internal soft-start and valley-current overcurrent protection. Its Constant-On-Time control dynamically adjusts on-time based on V_IN/V_OUT ratio to maintain stable frequency across input voltage range.

It features dual enable logic: ENLDO controls global regulator enable (including VCC and LDO), while EN independently toggles the buck converter and 300kHz CLK output. The LDO switches over to VOUT once VOUT exceeds 3.15V and PG asserts, eliminating LDO dropout loss during normal operation.

Key Specifications

Pinout & Package

Package: QFN-16 (3mm × 3mm, exposed thermal pad on underside). Pin mapping validated per MPS NB670 Rev. 1.02 datasheet, Page 5.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-current synchronous buck converter with auxiliary LDO applications.

Compared with MP2451DT-LF-Z and RT7295BGJ8F, the NB670GQ-Z uniquely integrates a 300kHz CLK output for isolated gate-drive generation and automatic LDO switchover-making it optimal for space-constrained computing platforms requiring coordinated power sequencing and minimal external components.

Availability

NB670GQ-Z is available at Aetrix Electronics and suitable for laptop computer mainboards, tablet PC I/O subsystems, and flat-panel display logic boards requiring stable component supply and long-term production continuity.

Supply support for NB670GQ-Z 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 NB670 belongs to MPS's high-current integrated buck converter product line, engineered specifically for compact, multi-rail computing and consumer electronics applications where integration of buck, LDO, and clock generation reduces solution size and improves power-tree reliability.

FAQ

What is the purpose of the CLK pin on NB670GQ-Z?

The CLK pin outputs a 300kHz square wave used to drive an external charge pump circuit-typically generating 12–15V to bias high-side load switches or display backlight drivers. It activates once VIN exceeds the UVLO threshold and remains active as long as EN is high, independent of LDO state.

How does the LDO switchover function work?

When VOUT rises above 3.15V and the PG signal asserts, the internal LDO regulator shuts off and an internal MOSFET connects the LDO output pin directly to VOUT. This switchover occurs with 20µs deglitch filtering to prevent false triggering during transient conditions, reducing quiescent loss during normal operation.

Can NB670GQ-Z operate with only ceramic output capacitors?

Yes. Unlike traditional COT controllers, NB670GQ-Z includes internal ramp compensation that ensures stability with zero-ESR ceramic capacitors-eliminating the need for bulk electrolytic or RC networks. A minimum 22µF X7R/X5R ceramic capacitor is recommended at VOUT.

What happens during an overcurrent event?

During overcurrent, the NB670GQ-Z triggers valley-current limiting using the low-side MOSFET's R_DS(ON) as a current-sense element. If the sensed current exceeds 8.5A, PWM cycles are blocked until the fault clears. Persistent overcurrent leads to UVP-triggered latch-off, resettable only by pulling EN low or cycling VIN.

Is NB670GQ-Z suitable for new designs?

No. The datasheet explicitly states "NOT RECOMMENDED FOR NEW DESIGNS." While fully functional and supported, MPS has superseded this part with newer-generation converters offering improved efficiency, lower quiescent current, and enhanced protection. Aetrix recommends evaluating MPQ4420A or MPQ4470 for new projects.

How is thermal performance managed in QFN-16 package?

The NB670GQ-Z uses the exposed thermal pad (pins 8,9,15,16) as primary heat path. With θ_JA = 70°C/W on a 4-layer PCB, it sustains 6A continuous load at +25°C ambient. For higher ambient or sustained peak loads, thermal vias under the pad and copper pour on inner layers are mandatory to maintain junction temperature below 125°C.

What is the role of AGND versus PGND?

AGND is the reference for analog circuits (error amplifier, reference, PG comparator) and must be routed separately from PGND-the high-current return path for switches and LDO. Connecting AGND to PGND only at the exposed pad minimizes noise coupling into feedback and regulation paths, preserving output voltage accuracy and transient response.