Semi-automatic mode operation of LTC4291-1 & LTC4291


I have a question about LTC4291-1 & LTC4292.

I am checking if the LTC4292 can be connected to the evaluation board (DC2911A) set to Class 8 of the LT4293 to supply power.

In Auto mode, power was supplied without problems when a Class 8 PD was connected to Port 1 and Port 2.

In semi-automatic mode, Port1 was able to supply power with Class8 without any problem.

However, if you continue to connect DC2911A to Port2, it will be judged as Class4 by PSE even though it is set to Class8.

At that time, the voltage was output only to OUT2A, and the voltage was not output from OUT2B.

Is there any possible cause?

When using in semi-automatic mode, PCUTn, CUTn, and LIMn are set so that Class 8 can be output.

Also, if Port2 is connected first, Port2 will be powered by Class8 and Port1 will be judged by Class4.

I would appreciate it if you could reply.

Best Regards,


  • Hello

    How is the confirmation status?

    When supplying multiple ports in Class 8 in semi-automatic mode, what status should be set?

    PCUTn, CUTn, LIMn are set to the level that Class8 can supply.

    Is there anything else I need to set?

    I would appreciate it if you could reply.

    Best Regards,


  • 0
    •  Analog Employees 
    on Dec 16, 2020 12:22 AM in reply to knj

    The fact that the PSE is working when in Auto mode, this tells me that the hardware is working properly.  Auto mode can be set by the AUTO pin and requires no host control.  The Semi-auto mode requires a host controller.  It seems that there is an error somewhere with your software configuration.  Please refer to the LTC4291 software interface datasheet for Semi-auto mode operation example code and flowchart.