Texas Instruments TIDA-010046, Руководство по конструкции

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System Overview
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16 TIDUES1A – October 2019 – Revised February 2020
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EMC Compliant 10/100-Mbps Ethernet PHY Reference Design With IEEE
802.3at Type-1 (
≤ 12.95 W) PoE-PD
2.4.7 PoE Power Injector Circuit on PSE Side Board
For the TPS23861 PoE-PSE based circuit design for injecting power onto any Ethernet cable for PoE
powered loads up to 30 W, refer to the
TIDA-00465 - Single Port, Power-over-Ethernet, Type 2 Auto-Mode
PSE Reference Design . Figure 12 shows the board layout for the TPS23861 PoE-PSE device.
Figure 12. TPS23861 PoE-PSE on PSE Side Board Layout
NOTE: Be sure the VPWR and VDD rails follow the proper power-up sequence. In this reference
design, the VPWR starts rising before the VDD rail which is the typical case because the
VDD rail is usually derived from the VPWR rail. The VDD rail will turn on when VPWR
reaches the externally programmed UVLO of the VDD rail. Also of note in
Figure 13 is that
RESET starts rising when VDD starts rising because the RESET pin is connected to the
VDD pin externally. Since only a single TPS23861 device is used in the system, then a
TPS7A4001 (LDO) can be used with R78 (RUP) = 825 k
Ω and R100 (RDOWN) = 32.4 k Ω .
For more details, see the TPS23861 Power-On Considerations application report.