Monolithic Power Systems Inc. MP9840GL-Z

Overview

MP9840GL-Z from Monolithic Power Systems is a synchronous step-down DC-DC converter with integrated 125mΩ high-side and 55mΩ low-side MOSFETs, delivering 3.5A continuous output across a 3.3V–36V input range. It features programmable 350kHz–2.5MHz switching frequency, 14μA no-load quiescent current, and power-good (PG) monitoring - enabling use in automotive infotainment power rails and battery-powered industrial sensors.

For engineers reviewing the MP9840GL-Z datasheet, MP9840GL-Z pinout, MP9840GL-Z application, or MP9840GL-Z equivalent, key selection criteria include its 80ns minimum on-time for high-duty-cycle operation, selectable forced CCM/AAM mode, hiccup over-current protection, and QFN-16 (3mm×4mm) thermal performance with θJA = 48°C/W.

Technical Context

The MP9840GL-Z employs peak-current-mode control with internal error amplifier and 0.8V reference for precise output regulation. Its dual-mode operation supports forced continuous conduction mode (CCM) for low ripple or advanced asynchronous mode (AAM) for ultra-low light-load efficiency down to 2μA shutdown current.

Bootstrap charging and BST refresh circuitry enable stable high-duty-cycle operation up to ~100%, while PHASE pin allows 180° phase synchronization of multiple units to reduce input ripple. The device integrates hiccup OCP, thermal shutdown at 170°C, and ±10% PG detection with 30μs deglitch timing.

Key Specifications

Pinout & Package

MP9840GL-Z is housed in a thermally enhanced QFN-16 package (3mm × 4mm, 0.5mm pitch) with exposed thermal pad (PGND-connected) for PCB-level heat dissipation. Pin 1 is marked with dot; top marking includes "MP" prefix, year/week code, and lot number.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous step-down converter applications.

Compared with MP9840GL-Z, MPQ4433AGL-A-Z trades frequency flexibility and phase control for lower BOM count, while LM61480RQR offers double the current and wider frequency range but lacks the 80ns min-on-time needed for extreme VIN/VOUT ratios.

Availability

MP9840GL-Z is available at Aetrix Electronics and suitable for automotive infotainment power, industrial sensor node supply, and medical portable diagnostic device applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP9840GL-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 MP9840 belongs to MPS's automotive-grade synchronous buck converter product line, engineered for high-voltage transient resilience, ultra-low quiescent current, and seamless integration into space-constrained, battery-sensitive systems.

FAQ

What is the maximum duty cycle achievable with MP9840GL-Z?

The MP9840GL-Z achieves effective duty cycles approaching 100% using BST refresh circuitry, which forces the low-side MOSFET on to recharge the bootstrap capacitor when BST–SW drops below 2.5V. This enables stable operation at VIN/VOUT ratios up to 36V/3.3V (~92% theoretical duty cycle), confirmed by test data showing regulation down to 2.9V output under 36V input.

Can MP9840GL-Z operate with a 24V input and 5V output without external components beyond the inductor and capacitors?

Yes - the MP9840GL-Z only requires an external inductor (e.g., 4.7μH), input/output capacitors, feedback resistors (e.g., 68.1kΩ/13kΩ for 5V), and optional BST capacitor. No external drivers, compensation networks, or bootstrap diodes are needed due to fully integrated power stage and optimized internal compensation.

How does the PHASE pin affect thermal performance when two MP9840GL-Z devices are paralleled?

Setting opposite PHASE logic (one high, one low) creates 180° out-of-phase switching, halving input current ripple amplitude. This reduces RMS input capacitor current by ~30%, lowering capacitor self-heating and allowing smaller, lower-ESR ceramics - indirectly improving overall thermal margin in dense layouts.

Is BIAS pin connection mandatory for automotive applications?

No - BIAS is optional. When left floating or tied to GND, the IC operates from VIN via internal regulator. However, connecting BIAS to a clean 5V rail (e.g., from a pre-regulator) reduces power dissipation by ~150mW at 3.5A/12V input, lowering junction temperature by ~7°C and improving reliability in 105°C ambient environments.

What failure modes trigger the hiccup OCP, and how long is the restart delay?

Hiccup OCP activates when output voltage collapses below 55% of nominal (e.g., <1.8V for 3.3V output) due to sustained overload or short circuit. The IC discharges the SS capacitor fully (time depends on CSS value) then restarts with full soft-start - typical cycle duration is 20–100ms depending on SS capacitance, preventing thermal damage while enabling automatic recovery.

Does MP9840GL-Z support pre-bias start-up, and how is it implemented?

Yes - pre-bias start-up is supported. If FB voltage exceeds SS – 150mV at startup (indicating existing output voltage), both HS and LS MOSFETs remain off until SS rises above FB. This prevents reverse current flow and uncontrolled inrush, verified in application note AN-107 with 3.3V pre-bias on 5V output configuration.