JAJSDX9C June 2017 – November 2018 TPS2373
PRODUCTION DATA.
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PG (power good or converter enable) is a pin that when at low level indicates when the internal hotswap MOSFET is in inrush phase. PG goes high impedance when inrush phase is over and can be used to enable a downstream converter to start up. Common interfaces to the converter controller include the soft-start or enable pins.
TPH, TPL and BT provide information relative to the PSE Type (1-2 or 3-4) and its allocated power. It can also indicate if the APD is driven high, in which case the code becomes "Low-High-High", respectively.
Using the APD encoding allows the PD to operate from an adapter at high-power if a PSE with enough power capability is not present, assuming the adapter has sufficient capacity. Applications must monitor the state of TPH, TPL and BT to detect power source transitions. Transitions could occur when a local power supply is added or dropped, or when a PSE is enabled on the far end. The PD may be required to adjust the load appropriately. The usage of TPH/TPL/BT is demonstrated in Figure 30.
The TPS2373 is also able to interoperate with non standard PoE++ PSE controllers. If powered from a PoE++ PSE controller, the TPH/TPL/BT 3-bit code becomes "Low-Low-High". This also indicates that the PoE++PSE agreed to deliver the power requested by the TPS2373.