Texas Instruments TPS23861EVM-612, Руководство пользователя, Страница: 4 / 39

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2.1.2 Local 3.3 V (Labeled 3.3V)
Local 3.3 V for local devices (labeled as 3.3V) is provided by the on-board LM5019 buck converter. The
LM5019 provides a basic power-on sequence and provides a well-controlled and consistent startup in
order to prevent erratic operation. This is described in detail in
SLVA723 . In addition to 48 V, the
TPS23861 requires 3.3 V for the digital circuitry and this is routed up to TPS23861EVM-613 over the
connector interface. The current consumption is 25-mA typical and 30-mA maximum.
2.1.3 External 3.3 V (Labeled 3.3V_USB)
The TPS23861EVM-612 provides galvanic isolation between PoE power side and host side using digital
isolators (ISO7241CD). The host side power is provided either from J2 (from USB-TO-GPIO) or J5 (from
LaunchPad). The current consumption is 3-mA typical and 5-mA maximum.
CAUTION
Do not use USB-TO-GPIO and LaunchPad simultaneously.
Table 1. TPS23861EVM-612 Voltage Rail Current Requirements
Voltage Rail Typical (mA) Maximum (mA)
3.3V_USB 2.5 3
3.3V 25 30
VPWR (Miscellaneous) 35 57
VPWR (8x Type 1
2992 3142
Output Ports)
VPWR (8x Type 2
5160 5418
Output Ports)
VPWR Total (8x Type 1
3027 3202
Ports)
VPWR Total (8x Type 2
5195 5478
Ports)
2.2 PoE Port Interfaces
The TPS23861 devices are pre-configured to operate in auto mode and, as such, no external
communication interface is required to enable or configure the TPS23861EVM-612. A standard PD can be
plugged into ports 1–4 and be expected to operate automatically.
2.2.1 Standard 30 W, IEEE802.3at Type 2 ports
Four standard ports are provided at J19, J20, J8, and J7 for two pair ports 1, 2, 3, and 4 respectively. The
power furnished is according to alternative A with MDI-X polarity.
2.2.2 Nonstandard 60-W Ports
Two non-standard ports are provided at J21 and J9 for four pair ports 1 and 2, respectively. The power
furnished is according to alternative A with MDI-X polarity and alternative B on a single port connector. A
standard PD may not power on at this interface, but a PD which can process power on all of the Ethernet
conductors (refer to TI application report,
SLVA625 ) can power on and consume up to 60 W.
2.3 I
2
C Interfaces
Two I
2
C interfaces to the TPS23861 are provided on the EVM.
2.3.1 USB-TO-GPIO
J2 provides an interface with the USB-TO-GPIO adapter when using a PC and GUI.
4 TPS23861EVM-612: Auto-Mode Evaluation Module for TPS23861 SLUUAY8C – March 2014 – Revised November 2015
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