Monolithic Power Systems Inc. MP2639AGR-Z

Overview

MP2639AGR-Z from Monolithic Power Systems is a switch-mode, bidirectional 2-cell Li-ion/Li-polymer battery management IC supporting USB-compliant 5V input charging and regulated 5V output discharge. It integrates step-up (charge) and step-down (discharge) DC/DC conversion, cell balancing (200mA), programmable charge current up to 2.5A, discharge current up to 5.0A, and 8.4V ±0.5% charge voltage accuracy. Used in power banks and portable power stations for dual-role energy routing.

For engineers reviewing the MP2639AGR-Z datasheet, MP2639AGR-Z pinout, MP2639AGR-Z application, or MP2639AGR-Z equivalent, key selection criteria include bidirectional topology validation, QFN-26 package thermal performance, NTC-based temperature monitoring implementation, cell balance threshold (∆VCELL = 65mV), and mode-controlled SW topology switching between Q1 (step-down) and Q2 (step-up).

Technical Context

The MP2639AGR-Z implements a dual-MOSFET synchronous buck-boost architecture with dedicated high-side (Q1) and low-side (Q2) NMOS switches, plus reverse-blocking MOSFET (QBR). In charge mode (MODE = low), it operates as a step-up converter with Q2 active and Q1 synchronous; in discharge mode (MODE = high), it functions as a step-down converter with Q1 active and Q2 synchronous.

It features integrated cell balancing via MID pin sensing, four-level voltage-based fuel gauge using LED1–LED4, and independent programmable limits: input current (via ILIM), charge current (ISET), discharge current (OLIM), and input voltage (VLIM). Thermal regulation maintains die temperature ≤120°C, with shutdown at 150°C junction limit.

Key Specifications

Pinout & Package

MP2639AGR-Z is housed in a thermally enhanced QFN-26 (4mm × 4mm) package with exposed thermal pad (Pin 5, PGND), optimized for power dissipation in portable battery systems.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional 2-cell battery management applications.

Compared with BQ25895RTWR and IP2326, MP2639AGR-Z uniquely delivers integrated cell balancing, programmable dual-limit power management, and hardware-enforced thermal regulation in a single QFN-26 package-enabling higher reliability and smaller footprint in dual-role portable power designs.

Availability

MP2639AGR-Z is available at Aetrix Electronics and suitable for power bank systems, portable power stations, and USB-C accessory designs requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for MP2639AGR-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 over two decades of leadership in DC/DC conversion and battery management solutions.

The MP2639A product line targets highly integrated, space-constrained portable power applications-designed specifically to replace multi-chip charger + boost architectures with a single, thermally robust, bidirectional solution for 2-cell Li-ion systems.

FAQ

What is the function of the MID pin in MP2639AGR-Z?

The MID pin connects to the midpoint of a 2-cell series battery to enable per-cell voltage monitoring. It allows the IC to detect individual cell overvoltage (≥4.21V/cell), initiate cell balancing when ∆VCELL exceeds 65mV, and prevent unsafe charging conditions that could cause thermal runaway or capacity imbalance.

How does MP2639AGR-Z handle thermal regulation during high-current operation?

MP2639AGR-Z employs dual-stage thermal protection: first, it reduces charge/discharge current via internal thermal foldback starting at 120°C die temperature; second, it triggers hard shutdown at 150°C junction limit. The QFN-26 package's exposed PGND pad must be soldered to a ≥100mm² copper thermal plane to maintain θJA ≤42°C/W and sustain 2.5A/5.0A operation.

Can MP2639AGR-Z operate without an NTC thermistor?

Yes-NTC functionality is optional. If not used, leave NTC pin open and disconnect VNTC from any external circuitry. The IC will skip temperature-based charge/discharge restrictions but retain all other protections (OVP, UVP, timer, short-circuit). Default operation assumes ambient-temperature safe zone (10–45°C).

What determines the transition between trickle, constant-current, and constant-voltage charge phases?

Transition is fully autonomous and voltage-triggered: trickle charge (300mA) activates below 5.9V battery voltage; CC phase begins at 5.9V and continues until VBATT reaches 8.38V; CV phase holds 8.4V until termination current drops to ≤10% of ICC (e.g., ≤250mA for 2.5A setting), verified by IB pin current monitoring.

Is the 5V discharge output regulated under varying battery voltage?

Yes-the discharge output is tightly regulated to 5.0V ±5% across the full 6.0V–8.7V battery input range. This is achieved via feedback loop on FB pin with 1.2V reference, combined with load trace compensation that adjusts duty cycle based on output current to counter IR drop in PCB traces and connectors.

How is cell balancing initiated and controlled?

Cell balancing starts automatically when MID voltage deviates from half-VH by ≥65mV (e.g., VH=8.4V → MID should be 4.2V; balance triggers if MID ≤4.135V or ≥4.265V). It applies 200mA balancing current between cells via internal FETs until ∆VCELL falls below 30mV hysteresis, limiting duration to prevent over-discharge of weaker cell.

What is the role of the PB pin during system startup?

The PB pin serves as a hardware-enabled discharge mode trigger. At power-on, if PB is held low for >2.5s before MODE is asserted, the IC enters discharge mode directly-even with no external MODE signal. This enables "instant-on" power bank behavior where pressing the button powers the 5V output without host MCU involvement.