Monolithic Power Systems Inc. NB669GQ-Z

Overview

NB669GQ-Z from Monolithic Power Systems is a fully integrated 24V-input synchronous buck converter with integrated 5V/100mA LDO and 300kHz CLK output, delivering 6A continuous / 9A peak output current at fixed 5V. It employs Constant-On-Time (COT) control, features internal 30mΩ/15mΩ MOSFETs, and targets high-density laptop and tablet power rails requiring fast transient response and auxiliary 5V supply.

For engineers reviewing the NB669GQ-Z datasheet, NB669GQ-Z pinout, NB669GQ-Z application, or NB669GQ-Z equivalent, this device serves as a compact, single-chip solution for primary 5V rail generation with integrated LDO and clock for external charge pumps-critical for notebook system power architecture validation and BOM consolidation.

Technical Context

The NB669GQ-Z integrates a COT-controlled synchronous buck stage with valley-current OCP, programmable UVLO via EN resistive divider, and dual enable logic (ENLDO for full chip shutdown, EN for buck+CLK control). Its internal 5V LDO switches over to VOUT once PG asserts, eliminating redundant regulation loss during active operation.

It delivers regulated 5V output with ±1% reference accuracy (4.95–5.15V), supports input range 6.5V–24V, and uses internal ramp compensation to stabilize ceramic-capacitor-based outputs-eliminating need for ESR-dependent compensation while maintaining <0.5ms PG delay and 25°C thermal hysteresis.

Key Specifications

Pinout & Package

Package: QFN16 (3mm × 3mm) with exposed thermal pad on underside - enables high-power density and low-θJC (15°C/W) thermal performance in space-constrained laptop PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2451DT-LF-Z and RT7290AZSP, NB669GQ-Z uniquely integrates LDO and CLK-reducing total BOM count by three devices and enabling single-rail power architecture in space-constrained systems where auxiliary 5V and gate drive voltage are co-located.

Availability

NB669GQ-Z is available at Aetrix Electronics and suitable for laptop computer power subsystems, tablet PC motherboard designs, and flat-panel display logic supplies requiring stable component supply across extended product lifecycles.

Supply support for NB669GQ-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 NB669 belongs to MPS's high-current integrated buck converter product line, engineered specifically for space-constrained computing and consumer electronics requiring consolidated 5V power with auxiliary functions.

FAQ

What is the function of the ENLDO pin versus the EN pin?

ENLDO is the global enable that controls the entire IC-including VCC regulator, LDO, buck stage, and CLK. When pulled low, it shuts down all internal circuitry. EN controls only the buck converter and CLK output; it remains functional even if ENLDO is high. This dual-enable structure allows independent control of main power and auxiliary functions-e.g., keeping LDO active during sleep while disabling the buck rail.

Does NB669GQ-Z support pre-biased output startup?

Yes. When the output is pre-biased at power-up, the NB669GQ-Z disables both high-side and low-side switches until the internal reference voltage exceeds the sensed VOUT level at the FB node. This prevents reverse current flow and ensures controlled ramp-up without output collapse or overshoot-critical for hot-swap and multi-rail systems.

How does the internal LDO switch over to VOUT?

The LDO automatically switches over to VOUT when VOUT reaches 4.77V and the PG signal asserts. An internal MOSFET connects the LDO output directly to VOUT, bypassing the linear regulator. A 20µs deglitch time prevents false triggering during transient events, ensuring glitch-free transition and eliminating 100mA LDO dropout loss during active operation.

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

The 300kHz CLK output drives external charge pump circuits to generate ~12–15V gate drive for high-side load switches. It sources/sinks ±5mA and maintains rail-to-rail swing (0.05V–4.95V). The output remains active as long as VIN exceeds UVLO and EN is high-enabling efficient gate drive without loading the main buck converter's efficiency.

Can NB669GQ-Z operate with only ceramic output capacitors?

Yes. Unlike traditional COT controllers, NB669GQ-Z incorporates internal ramp compensation that stabilizes the control loop without requiring ESR-based output capacitor damping. This allows pure ceramic capacitor designs-reducing output ripple, board area, and total BOM cost while maintaining stability across temperature and aging.

What happens during over-current fault and how is it reset?

During over-current, the NB669GQ-Z triggers valley-current limiting using the low-side MOSFET's R_DS(ON). If sustained, UVP follows due to output droop, latching off the high-side switch and turning on the low-side as a -1A sink. Fault latch resets only when EN is pulled low or VIN is power-cycled-preventing automatic recovery into unsafe conditions.

Is NB669GQ-Z still in active production or end-of-life?

The NB669 series is marked "END OF LIFE" in the official MPS documentation (Rev. 1.03, 2014). While Aetrix Electronics maintains legacy inventory and supports existing designs, new designs should consider MPS's newer-generation alternatives such as MPQ4420A or MPQ4470, which offer improved efficiency, smaller packages, and extended lifetime support.