All,

I"m using Netburners board to implement into a keyboard.
Ethernet Microprocessor Basically you take the netburner board and plug it into the board which I'm designing now. Once plugged in the keyboard will be able to talk over ethernet. So, it's in 3.3V DC system. We supply power @ 3.3V from the keyboard +5V DC power source with a 3pin regulator.

Since I supply power up to the Netburner board I wasn't sure what type of capacitance I should put on my board at the connector where the netburner boards connects in. Currently the design has a 10uF but am uncertain if this is enough. Also, I would assume having the cap as close to the connector would be a good idea to keep 3.3V stable on the PCB? Does anyone have an idea of how to know I have enough capacitance at the connector? The datasheet isn't helpfull and I called Netburner and have yet to hear a response.

 

Hi,

This question has much more to do with your power supply design rather then the NetBurner module it is powering. As with any microprocessor board or IC, you need to make sure that your power supply can provide the max voltage and current required by the device. Looking at the product web page, it says that the max power draw will be 450mA @ 3.3V. I use this NetBurner product and know that it usually draws an average current of about 300-310mA but it is a good idea to design your power supply to be able to provide the max current listed of 450mA. You also need to add in the current draw of any other components that are drawing power off this 3.3V rail.

You should find a switching or linear regulator to convert your 5V to 3.3V. Linear regulator power supplies are simpler to design but are inefficient since reduce the voltage by converting the energy to heat. Any linear regulator drawing this much current will likely need a heat sink. Switching regulators can handle much higher currents with no heat sink and are much more efficient. With a switcher you will likely draw under 350mA@5V where the linear will require the full 450mA@5V. I am not sure what the max current of your 5V supply is but this might be a deciding factor for your power supply design. The data sheet for the regulator you choose almost always provide a reference design for the power supply circuit. This is where you will find the capacitor values required for the voltage output and input of the regulator.

-Larry

 

Hi,

Forgot to address part of your question about capacitance close to the module voltage inputs. If you have a stable power supply design with low noise then it should not be necessary to put additional caps at the power inputs of the module. You can see that the NetBurner developer does not place additional capacitors here either. If you look at the module itself you will see that there are decoupling capacitors close to all the voltage input pins of the module and also next to all the components on the module.

-Larry