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SM72445

Michele Fiorino
Intellectual 405 points
Other Parts Discussed in Thread: SM72445, SM72442

Hello,

I'm Michele and I'm trying to build one battery charger using sm72445

I can put sm72445 in open loop mode, but in this mode I can't force it in boost mode: when I write in dc_open register value greater then 255, gate signal for gate 3 is always high. This causes short circuit for input voltage! Can you help me? 

  • 0
    TI__Guru**** 191445 points

    For a simple battery charger, SM72445 may not be the best choice.  It should be able to operate in as a boost converter in open loop mode.  In open loop mode, the duty cycle is fixed.  You set it by operation command from reg 3b13:5. set to 1and then assert & deassert bb_reset to put the device in openloop.  In open loop mode most of the chip control functions are disabled and and you will just be outputting fixed frequency and duty cycle.

    If you post your requirements we may be able to suggest a simpler option.

  • 0 in reply to JohnTucker
    Prodigy 50 points

    Hello John, I'm alessandro , a michele's friend.

    We have only one problem: we can't put the device in boost mode, neither in MPPT mode, nor in Open Loop mode

    1. In open loop mode, the 9bit register DC_open can't assume value greater than 255, but it is a 9bit register: from 0d to 254d it is in buck mode, 255d is panel mode, and I thought that value greater than 255 was for boost mode. But when I write value from 256d to 511d the gate signal 3 is always high, and then the input voltage is shorted.

    2. In MPPT mode, I can rise output voltage through vout_max register, but when output voltage engages input votage, the device goes into panel mode and I can modify output voltage no more.

    Why do you think sm72445 is not suitable for battery chager application?

    thanks

  • 0 in reply to alessandro fici
    TI__Guru**** 191445 points

    I don't really have any direct experience with the RM72445, but it is intended for solar panel conversion.  In MPPT mode, the converter will automatically switch between buck and boost modes depending on the input and output conditions.  If you are doing a simple battery charging application, then TI offers a whole catalog of suitable devices.  Many of these will not require so much tedious set up.  If you post your requirements we can suggest something.

  • 0 in reply to JohnTucker
    Prodigy 50 points

    Hi John,

    my project is intended for solar panel conversion, and it is based on AN-2121 with one difference: I replaced sm72442 with sm72445. I think this chip is fantastic for my application, and I only want get more information about it. My board is already mounted,  and so I need talk to anyone has direct experience with sm72445.

    Can you help me?

    thanks

    alessandro

  • 0 in reply to alessandro fici
    Prodigy 35 points

    I know this is an old topic, but did anyone found a solution for this problem?

    I just mounted an SM72445 board, the buck mode in MPPT and panel mode work great, but when I try to turn it on with a voltage on the output (supecapacitor with some charge) higher than the voltage on the input, it just don't work.

  • 0 in reply to Joao Gustavo Ceschin
    TI__Guru**** 191445 points

    I'm going to move this thread to the power, etc. forum.  If there is any chance of an answer you will find it there.

  • 0 in reply to JohnTucker
    Prodigy 90 points

    Hi,

    is there a way to disable the Panel Mode? Sometimes the SM72445 enters PM when that´s not the MPP.