The TPS2384 has three internal supply buses (10 V, 6.3 V and 3.3 V) generated from the 48-V input supply. These supplies are used to bias all internal digital and analog circuitry. Each supply has been brought out separately for proper bypassing to insure high performance. The digital supply (3.3 V) is available for powering external loads up to 2 mA. For more demanding loads TI highly recommends to use external buffers to prevent system degradation. When the TPS2384 is initially powered up an internal Power-on-Reset (POR) circuit resets all registers and sets all ports to the off state to ensure that the device is powered up in a known safe operating state.

The TPS2384 has three modes of operation: auto mode (AM), semi-auto mode (SAM), and power management mode (PMM).

• In auto mode the TPS2384 performs discovery, classification and delivery of power autonomously to a compliant PD without the need of a micro-controller.
• In semi-auto mode the TPS2384 operates in auto mode but users can access the contents of all read status registers and A/D registers through the I²C serial interface. All write control registers are active except for D0 through D3 of Port Control register 1 (Address 0010) for limited port control. The semi-auto mode allows the TPS2384 to detect valid PDs without micro-controller intervention but adds a flexibility to perform power management activities.
• Power management mode (with a micro-controller) allows users additional capabilities of discovering non-compliant (legacy) PDs, performing AC Disconnect and advanced power management system control that are based on real time port voltages and currents. All functions in this mode are programmed and controlled through read and write registers over the I²C interface. This feature allows users complete freedom in detecting and powering devices. A comprehensive software package is available that mates the power of the TPS2384 with the MSP430 micro-controller.

TPS2384 integrated output stage provides port power and low-side control. The internal low-side circuitry is designed with internal current sensing so there are no external resistors required. The output design ensures the power switches operate in the fully enhanced mode for low power dissipation.

The I²C interface allows easy application of opto-coupler circuitry to maintain Ethernet port isolation when a ground based micro-controller is required. The TPS2384 five address pins (A1–A5) allow the device to be addressed at one of 31 possible I²C addresses. Per-port write registers separately control each port state (discovery, classification, legacy, power up, and so on) while the read registers contain status information of the entire process along with parametric values of discovery, classification, and real-time port operating current, voltage and die temperature.

The proprietary 15-bit integrating A/D converter is designed to meet the harsh environment where the PSEPM resides. The converter is set for maximum rejection of power line noise allowing it to make accurate measurements of line currents during discovery, classification and power delivery for reliable power management decisions.