Nintendo Wii and DC/DC POL regulator module.

Discussion in 'The Projects Forum' started by cpqfe29, Feb 12, 2011.

  1. cpqfe29

    Thread Starter New Member

    Jan 30, 2010
    26
    1
    I have a Wii that is using a device called the WODE. It uses a USB port to power a screen and to send power to power a small external hard drive. I modified it to fit internally a 1.8 inch hard drive. My problem is that I need the other two ports for accesories such as a USB keyboard and headset. I am using a powered hub which works but I would like to keep this a self contained unit. (Back-story = off)

    I want to use the power from the power brick to power this DC/DC regulator. The Wii Brick can supply 3.7 Amps at 12 Volts DC.

    I want to solder 22 Gauge wire from where the power adapter connector connects to the main board and run that out the case to this WODE unit. In that base I want to connect the wires to a Texas Instruments PTH08080W. From there Output 5.4 volts [adjustable] to a tiny 4 port powered hub. (This module will supply the power instead of another wall wart.) 5.4 volts with the voltage drops gives me about 5V at the USB connectors. The hard drive uses 500mA (750mA at spin-up). The SATA to USB adapter converts this voltage down to 3.3 for the drive.

    Data Sheet. http://focus.ti.com/docs/prod/folders/print/pth08080w.html
    (Note: I also have a Lineage Power module also. - Data sheet --> http://www.lineagepower.com/oem/pdf/APXS002A0X.pdf) They are roughly the same device spec wise.

    Both the TI and the LP devices have an inhibit (on/off pin) that uses negative logic. When power is applied te device 'turns off'.

    I want the exact opposite. I want the device to be on when voltage is present at that pin. And since the brick will always be plugged in then there will always be a valid input source so the use of the pin is a must have option.

    Excerpt from the Data sheet:

    The Inhibit pin is an open-collector/drain-negative logic input that is referenced to GND. Applying a low-level ground signal to this input disables the module's output. When the Inhibit control is active, the input current drawn by the regulator is significantly reduced. If the Inhibit pin is left open-circuit, the module produces an output voltage whenever a valid input source is applied. Do not place an external pull-up on this pin.

    There is a spot on the motherboard that does NOT have power when the Wii is in standby or off mode. It goes to the fan power (5Volts). It is only active when the Wii is fully on.

    Question 1.
    What is a way to get this to work with positive logic? (When Wii is on then the module is on. When Wii is off then the module is off.)

    Question 2.
    If I use this fan power point to activate the module will it cause a voltage drop or other problems with the fan circuit? If so is there a way to minimize it?

    Note: On page 14 of the Lineage Power data sheet is shows [Figure 53 and 54]. It shows the difference between + and - logic control. Could I just apply that here externally. It shows an extra internal NPN transistor and some resistors. I should just be able to duplicate this on the outside to make it work that way i need it too correct?

    Sorry for the lengthy post. I try to provide as much information as I can.


    EDIT: This will be fused also. Any suggestions. A self resetting one may work for me as I would not want to open the case every time to replace. Or I can put some thing like this in the case. http://www.radioshack.com/product/index.jsp?productId=2062230

    Also I have a few tiny ferrite rings. Good idea or not to put a few turns on the power wire when I run this? The wire run will go along the side of the main board but it will go across 1/4 of it at one point.
     
    Last edited: Feb 12, 2011
  2. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    Too much for me but I can answer this one: Yes, it'll be easy to reverse the logic. I'd use a MOSFET as a switch, with your signal going to its gate, the source connected ground, and the drain sitting at the bottom of your module. When triggered ON by a voltage at the gate, the drain will be pulled very near ground and turn on the module. With no trigger, a resistor to ground will pull the gate voltage to ground, open the drain-to-source and thereby turn off the module.

    To choose the right N-channel MOSFET, you just need to know the current it must carry and the voltage of the trigger. Low voltage (5v) requires a logic-level MOSFET.
     
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  3. cpqfe29

    Thread Starter New Member

    Jan 30, 2010
    26
    1
    I will put is on a breadboard soon and test it out.

    Thank you for the information, it will give me a good starting point to work with.

    Does anyone have any information on

    Question 2.
    If I use this fan power point to activate the module will it cause a voltage drop or other problems with the fan circuit? If so is there a way to minimize it? (data sheet in original post).

    Anyone has a fuse /resettable fuse suggestion? It need to be self resetting or small so that I can drill a hole in the case to mount it (easily removable).
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    The Linear datasheet describes the idea also, except instead of the main power to the chip, you can just connect to the enable pin. Note that they sell units with either logic, so if you buy the right piece, it'll work directly.

    Re: The fan power. This should not be a problem to use because you will be going into a high impedance (ie. small) load. A circuit that can power a fan should be more than enough. However, you'll need to limit surge current if you're taking that power to the gate of the MOSFET, which essentially acts a capacitor. The load will be high until that cap (the gate) charges. It's a tiny capacitance, but use a resistor to limit the peak current to, say 10mA. Assume it's like connecting to ground and drops 5v at 10mA, so 500Ω should be good.
     
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