Monolithic Power Systems Inc. MP5991GLU-Z

Overview

MP5991GLU-Z from Monolithic Power Systems is a monolithic hot-swap Intelli-Fuse IC integrating a 1 mΩ R_DS(ON) power MOSFET, gate driver, current mirror, on-die temperature sensor, and 3.3 V LDO. It delivers up to 50 A continuous output current at room temperature (60 A with airflow), operates from 4–16 V input, and provides configurable over-current, short-circuit, and over-temperature protection in standalone or controller-coordinated mode for live backplane insertion.

For engineers reviewing the MP5991GLU-Z datasheet, MP5991GLU-Z pinout, MP5991GLU-Z application, or MP5991GLU-Z equivalent, this device serves as a system-level intelligent fuse solution-replacing discrete MOSFETs, sense resistors, and thermal sensors-with precise ±1% IMON reporting, fault-type indication (FLT_TYPE), parallel operation support, and GOK latched fault signaling for server, networking, and storage hot-swap subsystems.

Technical Context

The MP5991 implements closed-loop current limiting via real-time CS voltage comparison against OCREF/OCWREF and dynamic VGATE control during soft-start and fault conditions. Its integrated current mirror enables high-accuracy (±1%) analog IMON output without external shunt resistors, while the VTEMP pin provides linear 8.7 mV/°C junction temperature sensing.

Operation modes-including latch-off, hiccup (250/500/1000 ms auto-retry), and slave-are selected via resistor-programmed MODE pin voltage. Fault detection includes MOSFET drain-source/gate-source shorts (with entry/recovery thresholds at 85–95% and 65–75% of VIN), OVP (17–20 V), and OTP (145 °C), all reported through open-drain GOK and multi-level FLT_TYPE voltage encoding.

Key Specifications

Pinout & Package

LGA-32 (5 mm × 5 mm) package with exposed thermal pad; RoHS-compliant, lead-free, halogen-free construction.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar hot-swap fuse applications.

Compared with MP5920 (master-only controller) and TPS2491 (external-FET controller), MP5991GLU-Z uniquely integrates MOSFET, ±1% IMON, VTEMP, and FLT_TYPE in one LGA-32 package-reducing total solution size by ≥35% and enabling per-rail diagnostics without additional components.

Availability

MP5991GLU-Z is available at Aetrix Electronics and suitable for server blade insertion, modular storage enclosures, telecom line cards, and industrial PLC backplanes requiring stable component supply, full lifecycle traceability, and long-term production continuity.

Supply support for MP5991GLU-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 power management ICs, with design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The MP5991 belongs to MPS's Intelli-Fuse product line, engineered specifically for high-current hot-swap applications in datacenter, telecom, and industrial infrastructure-where integration, accuracy, and fault intelligence replace legacy discrete fuse and controller architectures.

FAQ

What is the maximum continuous output current rating for MP5991GLU-Z under natural convection?

The MP5991GLU-Z delivers 50 A continuous output current at 25 °C ambient temperature with no forced airflow. This rating is validated per the SOA curve in the datasheet (Figure 14) and assumes proper PCB copper pour (2 oz, 4-layer) and thermal pad soldering. Exceeding 50 A without airflow risks thermal shutdown at junction temperatures above 145 °C.

How does the MP5991 detect MOSFET drain-to-source short conditions?

The MP5991 monitors VOUT relative to VIN during startup: if VOUT rises to 85–95% of VIN before expected, it triggers DS short detection. Recovery occurs only after VOUT drops below 65–75% of VIN. This behavior is implemented in hardware and reported via FLT_TYPE = 0.57–0.63 V, independent of software polling.

Can MP5991GLU-Z operate without an external current-sense resistor?

Yes. The MP5991 uses an integrated current mirror to generate IMON (10 µA/A) and CS (10 µA/A) signals directly from the internal MOSFET channel, eliminating the need for external shunt resistors. External resistors are only required on IMON and CS pins to convert these currents to measurable voltages (e.g., 2 kΩ for 20 mV/A).

What configuration is required to enable hiccup-mode over-current protection?

Hiccup mode is selected by connecting a resistor between MODE and GND: 30 kΩ enables 250 ms retry, 0 Ω enables 500 ms, and 60 kΩ enables 1 s. The corresponding MODE pin voltage must fall within specified ranges (e.g., 0.24–0.36 V for 250 ms). No firmware or register writes are needed-operation is purely analog and immediate.

Is parallel operation of multiple MP5991 devices supported, and how is current sharing ensured?

Yes, MP5991 supports 2–3-phase parallel operation with active current sharing during both startup and steady state. Sharing is achieved via matched internal current-sense gain and synchronized soft-start ramping, as verified in Figure 19 showing <5% VCS mismatch across three devices at 45 A total load.

What is the purpose of the SCREF_OCWREF pin, and how is it used in standalone vs. slave mode?

In standalone mode, SCREF_OCWREF sets short-circuit current limit (ILIMIT_SC) by sampling VSCREF during t_{ON_DELAY}, selecting 40–120 A levels. In slave mode, it serves as OC warning reference (VOCWREF) for D_OC assertion. The same pin performs both functions based on MODE configuration-no external reconfiguration is required.

Does MP5991GLU-Z include over-voltage protection, and what is its trip threshold?

Yes. MP5991 includes input over-voltage protection (OVP) that trips at 17–20 V (typical 18.5 V), with 1 V hysteresis. When triggered, GOK latches low and FLT_TYPE outputs 0.865–0.935 V to indicate OV fault. The OVP circuit is internal and requires no external components.