Monolithic Power Systems Inc. NB670AGQ-Z

Overview

NB670AGQ-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 (COT) control for fast transient response, and includes OCP, OVP, UVP, thermal shutdown, and output discharge - deployed in laptop power rails and tablet DC-DC subsystems.

For engineers reviewing the NB670AGQ-Z datasheet, NB670AGQ-Z pinout, NB670AGQ-Z application, or NB670AGQ-Z equivalent, key selection considerations include its dual-regulator architecture (buck + LDO), 500kHz switching frequency, internal MOSFET R_DS(ON) (30mΩ HS / 15mΩ LS), PG signal timing (0.5ms delay), and ENLDO/EN dual-enable logic for system-level power sequencing.

Technical Context

The NB670AGQ-Z implements a COT-controlled synchronous buck topology with valley-current overcurrent protection using low-side MOSFET R_DS(ON) sensing. Its internal 5V VCC regulator powers control circuitry, while the 3.3V LDO switches over to VOUT once output reaches 3.15V and PG asserts.

It integrates a dedicated 300kHz open-drain CLK output for driving external charge pumps, independent of main converter operation. The PG signal is an open-drain output with 95% V_OUT rising threshold and 85% falling threshold, plus 0.5ms deglitch delay - enabling reliable system power-good handshaking.

Key Specifications

Pinout & Package

Package: QFN-16 (3mm × 3mm, exposed thermal pad). Pin count: 16 terminals (including 2 SW pins, 2 exposed pad connections).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2315GQ-Z and RT7295BGJ8F, the NB670AGQ-Z uniquely combines buck regulation, 3.3V LDO, and 300kHz CLK in one QFN-16 package - reducing BOM count and layout complexity for space-constrained portable systems requiring coordinated power sequencing.

Availability

NB670AGQ-Z is available at Aetrix Electronics and suitable for laptop computer power subsystems, tablet PC core logic supplies, and flat-panel display timing controller rails requiring stable component supply across extended product lifecycles.

Supply support for NB670AGQ-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.

The NB670AGQ-Z belongs to MPS's high-current integrated buck converter product line, engineered specifically for compact, multi-rail portable computing platforms requiring co-located main and auxiliary regulation with precise power sequencing.

FAQ

What is the purpose of the dual enable pins EN and ENLDO?

ENLDO controls global power: when low, it disables VCC, the buck converter, LDO, and CLK. EN controls only the buck regulator and CLK output. This separation enables flexible power sequencing - for example, keeping VCC active for monitoring while disabling the main rail during standby. EN must be actively driven; floating EN causes undefined behavior.

Does the NB670AGQ-Z require external compensation components?

No. The NB670AGQ-Z uses internal ramp compensation with its Constant-On-Time control architecture, enabling stable operation with ceramic output capacitors alone. No external RC network or type-II/type-III compensation is needed - simplifying layout and reducing BOM count compared to voltage-mode controllers.

How does the LDO switch-over function work?

At startup, the internal 3.3V LDO powers peripherals. Once VOUT reaches 3.15V and the PG signal asserts (after 0.5ms), an internal MOSFET connects the LDO output to VOUT, disconnecting the linear regulator. This reduces quiescent power loss during normal operation while maintaining seamless 3.3V supply continuity.

What is the role of the CLK output, and what load can it drive?

The CLK pin delivers a robust 300kHz square wave capable of sinking/source ±5mA. It is designed to drive external charge pump circuits (e.g., Dickson or voltage doubler) generating ~12–15V for high-side gate drivers. Its operation is independent of buck regulation status once VIN exceeds UVLO (4.65V).

Can the NB670AGQ-Z operate with pre-biased output?

Yes. If VOUT is pre-biased above the internal feedback voltage during startup, the NB670AGQ-Z disables both high-side and low-side switches until the internal reference ramps up past the sensed VOUT level. This prevents reverse current flow and ensures controlled, glitch-free power-up.

Is the NB670AGQ-Z RoHS-compliant and lead-free?

Yes. The NB670AGQ-Z is lead-free and fully compliant with the EU RoHS directive. All packaging materials and die attach meet RoHS Annex II substance restrictions. MPS publishes green status documentation on its website under Products → Quality Assurance.

Why is the NB670AGQ-Z marked "NOT RECOMMENDED FOR NEW DESIGNS"?

This designation reflects MPS's product lifecycle policy: newer alternatives (e.g., MP2315 series) offer improved efficiency, smaller footprint, or enhanced protection features. However, NB670AGQ-Z remains fully supported for existing designs, with guaranteed supply and full datasheet compliance through announced end-of-life dates.