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LTC4266 detect function in auto mode ?

Hi, all,

good day!

I meet a question, it is "how many detect function when LTC4266 work in auto mode ?" 

My customer got some information of micro semi PD69204 from micro semi FAE..

He says PD69104 has Current and power detection when IC work in auto mode.

Do our LTC4266 or LTC4290+4271 has the same function ?? 

i see LTC4266 spec has MOSFET fault detection and current detection ( ICUT and ILIMIT)

But customer want to know does our IC have over power protection every ports when IC work in auto mode??



  • To the original question about detect function, detection typically refers to the probing of the power interface for a valid PD signature.


    In auto mode with the LTC4266 AUTO pin high, each port will detect and classify repeatedly until a PD is discovered, set ICUT and ILIM according to the classification results, apply power after successful detection, and remove power when a PD is disconnected. Refer to Table 2 in theLTC4266 datasheet for the ICUT and ILIM values. The automatic setting of the ICUT and ILIM values only occurs if the LTC4266 is reset with the AUTO pin high.


    Per the IEEE specification, the LTC4266 will allow the port current to exceed ICUT for a limited period of time before removing power from the port, whereas it will actively control the MOSFET gate drive to keep the port current below ILIM. The port does not take any action to limit the current when only the ICUT threshold is exceeded, but does start the tCUT timer. The tLIM timer starts when the ILIM threshold is exceeded and current limit is active. If the current drops below the ICUT current threshold before its timer expires, the tCUT timer counts back down, but at 1/16 the rate that it counts up. This allows the current limit circuitry to tolerate intermittent overload signals with duty cycles below about 6%; longer duty cycle overloads will turn the port off.


    ICUT is typically set to a lower value than ILIM to allow the port to tolerate minor faults without current limiting.


    Per the IEEE specification, the LTC4266 will automatically set ILIM to 425mA (shown in bold in Table 5) during inrush at port turn-on, and then switch to the programmed ILIM setting once inrush has completed. To maintain IEEE compliance, ILIM should kept at 425mA for all Type 1 PDs, and 850mA if a Type 2 PD is detected. ILIM is automatically reset to 425mA when a port turns off.


    An AGND-VEE voltage within the range specified in the Electrical Characteristics of the LTC4266 datasheet will ensure that the PD will receive the full power it is requesting over the full cable channel resistance specified in the IEEE802.3at standard.  The port power is limited to the supply voltage and the ICUT and ILIM values.


    This operation is the same with the LTC4290/LTC4271 chipset.