HX2LP :The number of bus-power support port

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NXTY_Nagata
Level 4
Level 4
Distributor - NEXTY (Japan)
5 solutions authored First solution authored 100 sign-ins

Dear All,

About the AN69235 of the application note,

In the red circle,this document says HX2LP can support up to THREE downstream ports.

NXTY_Nagata_0-1623836145556.png

Could you tell me why HX2LP cannot support ALL(FOUR) downstream ports with bus-power?

Regards,

Nagata

 

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MallikaK_22
Moderator
Moderator
Moderator
50 likes received 750 replies posted 250 solutions authored

Hi,

The host provides 500mA for a bus powered upstream port. If a HX2LP hub is connected to the port, it's power consumption is around 230 mA (5V) as mentioned in the App Note. Now, when a device is plugged in to the downstream ports of the hub, it expects to be able to consume 100mA power in bus -powered mode.

This implies if 4 downstream ports are supported, the hub should be able to provide 400mA in total (100mA to each port). But since HX2LP itself consumes 230mA power out of the 500mA it drew from the upstream port, not enough power is left which HX2LP can provide to 4 downstream ports (400mA required). That is why, HX2LP can only support up to 3 downstream ports.

Kindly let me know if you need further clarifications.

Regards,

Mallika

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MallikaK_22
Moderator
Moderator
Moderator
50 likes received 750 replies posted 250 solutions authored

Hi,

The host provides 500mA for a bus powered upstream port. If a HX2LP hub is connected to the port, it's power consumption is around 230 mA (5V) as mentioned in the App Note. Now, when a device is plugged in to the downstream ports of the hub, it expects to be able to consume 100mA power in bus -powered mode.

This implies if 4 downstream ports are supported, the hub should be able to provide 400mA in total (100mA to each port). But since HX2LP itself consumes 230mA power out of the 500mA it drew from the upstream port, not enough power is left which HX2LP can provide to 4 downstream ports (400mA required). That is why, HX2LP can only support up to 3 downstream ports.

Kindly let me know if you need further clarifications.

Regards,

Mallika

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NXTY_Nagata
Level 4
Level 4
Distributor - NEXTY (Japan)
5 solutions authored First solution authored 100 sign-ins

Hello Mallika,

Thank you for your support.

I understand it.

Regards,

Nagata

HX2VlL

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