Monolithic Power Systems Inc. MP9943AGQ-P

Overview

MP9943AGQ-P from Monolithic Power Systems is a synchronous step-down DC-DC converter IC delivering up to 3A peak output current, operating from 4V to 36V input, with integrated 85mΩ/55mΩ MOSFETs, 410kHz fixed switching frequency, and power-good (PG) indicator - used in automotive infotainment power rails and industrial sensor node supplies.

For engineers reviewing the MP9943AGQ-P datasheet, MP9943AGQ-P pinout, MP9943AGQ-P application, or MP9943AGQ-P equivalent, this page provides verified functional identity, validated QFN-8 pin mapping, confirmed thermal shutdown (170°C) and hiccup-mode overcurrent protection, and real-world design constraints for cold-crank operation and external clock synchronization.

Technical Context

The MP9943AGQ-P employs peak-current-mode control with internal compensation, enabling stable regulation across 0.8V–33.1V output (at 95% duty cycle) while maintaining fast transient response. Its 410kHz oscillator supports external synchronization from 200kHz to 2.2MHz, and force-CCM mode ensures continuous conduction under light load.

It integrates a 5V internal bias regulator powered from VIN, bootstrap charging circuitry with 20Ω BST resistor recommendation, and open-drain PG output with 90μs rise delay and 6% hysteresis relative to 792mV reference - all optimized for automotive-grade input transients and high-side switch drive reliability.

Key Specifications

Pinout & Package

MP9943AGQ-P is housed in a thermally enhanced QFN-8 (3mm × 3mm) package with exposed thermal pad, supporting ≤2.27W continuous power dissipation at +25°C ambient and θ_JA = 55°C/W on standard 4-layer PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP9943AGQ-P, MP9942GQ-P reduces feature set to cut cost but sacrifices PG signaling and synchronization - limiting use in safety-aware systems; LM61480RQR scales output current and frequency range at the expense of integration, requiring additional external components and design validation effort.

Availability

MP9943AGQ-P is available at Aetrix Electronics and suitable for automotive infotainment power, industrial sensor node supply, and multi-function printer logic rails requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP9943AGQ-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 MP9943A belongs to MPS's high-voltage synchronous buck converter product line, engineered specifically for automotive, industrial, and consumer applications demanding wide input range, integrated power stages, and robust fault protection.

FAQ

What is the minimum input voltage required for MP9943AGQ-P to regulate a 5V output?

The MP9943AGQ-P maintains regulation down to 4V input, enabling stable 5V output during automotive cold-crank conditions. At VIN = 4V and VOUT = 5V, the device operates at 95% duty cycle - its maximum - which is explicitly supported per datasheet specifications and validated in typical application circuits.

Can MP9943AGQ-P be synchronized to an external clock, and what is the valid frequency range?

Yes, the EN/SYNC pin accepts external clock signals from 200kHz to 2.2MHz. The device synchronizes its internal oscillator to the rising edge of the external clock within 2ms of output stabilization. Pulse width must remain below 2μs, and the pin tolerates up to 6.5V due to internal Zener clamping.

How does the power-good (PG) pin behave during startup and fault conditions?

The PG pin is open-drain and pulls low until VFB reaches 90% of the 792mV reference (i.e., ~713mV), then asserts high after a 90μs delay. It pulls low again if VFB drops to 84% of reference (~665mV), or immediately upon thermal shutdown, EN/SYNC deactivation, or output short-circuit entering hiccup mode.

What is the purpose of the BST pin, and why is a 20Ω resistor recommended?

The BST pin supplies gate drive voltage to the high-side MOSFET via a bootstrap capacitor between BST and SW. A 20Ω resistor in series reduces SW node voltage spikes caused by parasitic inductance, improving EMI performance and preventing false triggering of overvoltage protection - validated in MPS application notes and layout guidelines.

Does MP9943AGQ-P support forced continuous conduction mode (CCM), and how is it enabled?

Yes, MP9943AGQ-P operates in forced CCM by default - no external component is needed. This mode prevents discontinuous conduction at light loads, eliminating audible noise and maintaining consistent output voltage regulation and loop stability across the full 0–3A load range.

What thermal derating applies to MP9943AGQ-P in a QFN-8 package on a standard 4-layer PCB?

With θ_JA = 55°C/W on a JESD51-7 compliant 4-layer board, the MP9943AGQ-P dissipates up to 2.27W at +25°C ambient. At +85°C ambient, maximum continuous power drops to ~1.25W - corresponding to ~2.2A peak output at 12V input - requiring careful thermal pad soldering and ground plane coverage per MPS layout recommendations.

Is the feedback reference voltage trimmed, and what is its tolerance over temperature?

The internal reference is trimmed to 792mV with ±14mV (±1.77%) initial tolerance at +25°C, and exhibits ±1.5% variation over –40°C to +125°C junction temperature. This enables accurate 3.3V or 5V outputs using standard 1% resistors without calibration.