MP3921 IEEE 802.3af/at PSE Controller QFN-32
MP3921 IEEE 802.3af/at PSE Controller QFN-32

MP3921 IEEE 802.3af/at PSE Controller QFN-32

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pMPS MP3921 — IEEE 802.3af/at PSE Controller, QFN-32./p
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    MP3921 IEEE 802.3af/at PSE Controller QFN-32

    The MPS MP3921 is a IEEE 802.3af/at PSE Controller. It is supplied in a QFN-32 package.

    The MP3921 is a single-port power-sourcing equipment (PSE) power controller for IEEE 802.3af/at-compliant power over Ethernet (PoE) applications.

    Key Specifications

    Part NumberMP3921
    FunctionIEEE 802.3af/at PSE Controller
    InterfaceI²C
    PackageQFN-32
    Ordering CodesMP3921

    Features

    • IEEE802.3af/at Compliant
    • 0.25Ω Current-Sense Resistor (RSENSE)
    • Automatic Mode and I2C Command Control Mode
    • Internal VCC Power Supply
    • Three-Wire I2C Interface for Isolated Applications
    • Two INT Pins for Interrupt Priority Selection
    • Disconnected DC Load Detection
    • Instantaneous Current/Voltage Readout
    • Configurable I2C Address
    • Thermal Protection

    Typical Application Circuit

    MP3921 typical application circuit
    MP3921 typical application circuit, as published in the MPS datasheet.

    Applications

    • Power-Sourcing Equipment (PSE) Switches/Routers
    • PSE Midspan Power Injectors

    Design Notes

    • Rail sequencing order and delay are part of the SoC power-up contract; a wrong order latches the processor even though every rail is in spec.
    • In multiphase designs, current balance depends on the loop matching between phases, so keep the layout symmetric.
    • Digital interfaces (PMBus, I²C) need pull-ups to the correct rail and a defined state during power-up.
    • Thermal design is a system problem here: the PMIC sits next to the load it feeds, so budget the shared copper, not the package alone.

    Common Questions

    Which package and ordering codes apply to the MP3921?
    QFN-32; order codes include MP3921.
    What are the defining features of the MP3921?
    IEEE802.3af/at Compliant 0.25Ω Current-Sense Resistor (RSENSE)

    Shenzhen Gaorunxin Technology Co., Ltd

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