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SM72442 and SM72295

Prodigy 10 points

Replies: 2

Views: 1368

Hi,

I am using SM72442, SM72295, and the MSP430 to design a charge controller. I want this controller to be able to handle 500W of power. It will have a 24V battery and need to handle 30A of current. The solar panel can range from 20V to 30V. Some parts I've ordered so far are below:

-csd17311q5 as the MOSFETS

-SER2915H-472KL which is the inductor with 4.7uH, Isat at 40A, Irms at 30A

-PF1262-0R02J2 which is the shunt resistor it is .02Ohm at 20W

My questions are:

1) Am I going in the correct direction so far?

2) Can I tell the SM72442 to output a particular voltage that I choose? (The battery doesn't always want Max Power Point (MPP) and has a charge schedule. I want to know if the SM72442 can have the charge schedule or that the MSP430 can tell it the charge schedule.)

3) Is the shunt resistor correct? I'm not sure how it is used by the SM72442. Do I need to do a voltage divider or anything of the sort to make sure it is in a correct range?

4) A lot of designs have zener diodes which i assume is for protection of the system can I get away with not using them from prototype purposes?

5) I also need to know the resistor values for RB1 through RB4 as well as RFB1 assuming RFB2 is 2kohms and RT1 is 20Kohms.

I'm completely new to all of this not even out of school yet (last semester can't wait!) any and all help is appreciated.

Thanks,

Randall Lay

2 Replies

  • Randall,

    I believe you are going in correct direction.

    You need to be sure the FETs are able to handle the current. I recommend 60 A FETs, with a minimum of 40 A.

    With the SM7442, look at the capacitive charge on the gate to make sure there is enough current on the output of the part. Make sure there is enough current at the drivers

     

    You should be able to set it to whatever voltage because there is a feedback pin from Vout. It has current sense and voltage sense on the output so you can track it.

    Find out the max current and size your shunt resistor so it fills up entire dynamic range. It depends on the current inputs

      

    Look at reference designs and application notes for additional guidance.

    Also take a look at National Semiconductor's site solarmajic.com

  • In reply to Sean Casserly:

    hello sir,

             we are students and working in a project of MPPT CHARGE CONTROLLER FOR SOLAR INVERTER.

    In this project we face some problems in design aspects.

    For your kind reference we attach a circuit we have with this mail

    1. we have a serious doubt of whether the micro controller (PIC16F722-E/SS) circuit is essential for proper working of controller.

    2.Next, in that design they play with TEMP sensor, is this temp sensor(SM72480) is must or not?

    3.Is this attached (our) design is possible to be developed on a single layer PCB board?

    Sir we are waiting for your kind notice....

    Thank you sir,

    with regards,

    CLINTON SKT

    SM3320-BATT_EV_Schematic.PDF

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