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About LTC-3862 Multi-Phase Current Mode Step-Up DC/DC Controller

Category: Hardware
Product Number: LTC-3862

Hi, I'm Nebi.

I have a question about LTC-3862 Multi-Phase Current Mode Step-Up DC/DC Controller.

This IC can operate multi phase operation for 2,3,4,6 and 12 phase operation. There is a 6-phase application example in the datasheet, but there is no 12-phase operation example. The datasheet does not give how to connect the PHASEMODE  pins of 6 ICs for 12-phase operation. 

Could you explain how to connect the PHASEMODE pins of the IC for 12-phase application?

I'm doing a 12 phase application but the phases don't shift 30 degrees. For this reason, current sharing is not correct. 

Do you have experience with this, what would you suggest as a solution?

Additionally, the CLKOUT signal is not exactly a pulse wave like square wave. The CLKOUT signal is in the form of a ramp. This ramp is also observed in the DC2006A-A code demo circuit.

Does the unevenness of the CLKOUT signal also disturb the phase shift? What would you recommend to fix the CLKOUT signal?

Best regards.

  • Hi Nebi,

    In a 12-phase application, I think it follows the 6-phase connection but with an additional connection in which the CLKOUT of the 3rd controller connects to the SYNC pin of the 4th controller.

    Connecting more than 2 Ith pins may not work. You might need to use an external OPAMP to drive the ITH pins.

  • Hi Ron,

    In multi-phase operation, the CLKOUT and SYNC pins of consecutive ICs must be connected to each other.
    In 6-phase application, 60 degree phase shift is made by leaving the PHASEMODE pins float.

    In 12-phase application, the phase shift should be 30 degrees. How to connect the PHASEMODE pin for 30 degree phase shift?

    As you said, if I make the same connection with 6 phases, it will not shift 30 degrees.

    Best regards.

  • Hi,

    According to the product expert, high phase applications such as 6 and 12 phase may be a challenge. They have only done two IC (4-phase) design. The information for more than 4-phases in the datasheet was not verified by building and testing a circuit.

  • Hi Ron,

    In the datasheet, there is information that work can be done for 6 and 12 phases.

    I determined the combination for 12 phase application according to Table 1.

    I also ran the simulation in the LTspice program. I have verified that there is 30 degree shift for 12 phases in simulation.
    In the circuit my demo design, some phases shift 30 degrees, some phases 60 degrees.This situation is interesting.

    How can you help with this?