MP9943GQ-Z (MPS Monolithic Power Systems Synchronous Step-Down DC-DC Converter, Buck Power IC)

MPS (Monolithic Power Systems) high-frequency synchronous rectification step-down switching power IC. It integrates high-side and low-side power MOSFETs, adopts current-mode control, delivers up to 3A continuous output, and supports wide input voltage range. Packaged in compact QFN8, it is ideal for 24V bus step-down applications in industrial and auxiliary automotive systems to supply power for MCUs, sensors, motor drivers and other components.

## Key Specifications

1. Topology: Synchronous Buck converter with integrated high-side and low-side NMOS

2. Input Voltage VIN: 4V ~ 36V (maximum transient rating 36V, supports automotive cold start)

3. Output Voltage VOUT: 0.8V ~ 28.5V (adjustable via FB divider resistors)

4. Output Current: Continuous 3A, peak 3A

5. Integrated MOS Rds(on): 85mΩ high-side / 55mΩ low-side

6. Switching Frequency: Internally fixed at 410kHz; supports external clock synchronization from 200kHz to 2.2MHz

7. Control Scheme: Current-mode PWM with PSM power-saving mode at light load

8. Temperature Range: -40℃ ~ +125℃ (Junction Temperature TJ)

9. Package: QFN-8 (3mm×3mm with exposed thermal pad), tape & reel

10. Protection Features: Internal soft-start, hiccup-mode OCP overcurrent protection, TSD thermal shutdown, UVLO undervoltage lockout

11. Additional Pins: PG Power Good signal; EN enable pin multiplexed for frequency synchronization

12. Quiescent Current: Typical 500μA under light load condition

## Functions

1. High-to-low voltage DC-DC step-down conversion: Wide 4~36V input, stabilizes 24V/12V bus down to 5V, 3.3V, 1.8V etc. to power main controllers, sensors and driver ICs.

2. High efficiency via synchronous rectification: Integrated high/low side MOSFETs generate less heat compared with non-synchronous Buck using diodes; peak efficiency up to 95%.

3. Current-mode control: Fast transient response, easy loop compensation and small voltage fluctuation during load steps.

4. Enable and frequency synchronization: EN pin turns power supply on/off. External clock synchronization is available to reduce system EMI noise.

5. PG Power Good indicator: Open-drain output to notify MCU once output voltage is within regulation for power-up sequence management.

6. Internal soft-start: Gradually ramps up output voltage during power-on to suppress inrush current and protect downstream loads.

7. Multi-protection: Auto-recovery hiccup overcurrent, thermal shutdown and undervoltage lockout. Automatic retry after fault improves system reliability.

8. Light-load power saving mode: Reduces switching loss under light load to improve standby efficiency.

## Applications

- Industrial Control: PLC modules, industrial IO boards, 24V bus-powered acquisition boards, sensor transmitters

- Robotics: Small mobile robots, gimbal power boards, power supply for MCU and motor drivers (perfect match with the EFM8BB21 + DRV8251 solution above)

- Automotive Auxiliary: Auxiliary automotive electronic control, cold start scenarios, on-board peripheral power supply (non-AEC-Q qualified, for general automotive accessories only)

- Networking & Communication: Gateways, small switches, security cameras

- Medical Devices: Power supply for portable medical detection modules

- Consumer Devices: Power tools, water pump controllers