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Offline msrinivasan1995

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regarding mosfet selection
« on: February 24, 2017, 04:59:12 PM »
I'm designing Li-ion charger using BQ24650. I have selected a N-channel MOSFETo. I'm entirely new to work with this type of MOSFET with higher ratings. Can anybody suggest me how to connect it in the PCB since there are 4 drains, 3 source and one gate. I dont know how to connect it. I basically read that there are more types of drains and source's just to manage the stress caused due to high power. Can anyone help me how to make it in the PCB layout in Eagle. The mosfet i Have decided is http://www.ti.com/product/csd18512q5b/datasheet.
 

Offline rachaelp

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Re: regarding mosfet selection
« Reply #1 on: February 25, 2017, 03:18:13 AM »
I'm designing Li-ion charger using BQ24650. I have selected a N-channel MOSFETo. I'm entirely new to work with this type of MOSFET with higher ratings. Can anybody suggest me how to connect it in the PCB since there are 4 drains, 3 source and one gate. I dont know how to connect it. I basically read that there are more types of drains and source's just to manage the stress caused due to high power. Can anyone help me how to make it in the PCB layout in Eagle. The mosfet i Have decided is http://www.ti.com/product/csd18512q5b/datasheet.

There was an almost identical question on the Element 14 forums a few weeks ago. Was that you?

The answer is simple, the part has 4 pins for the drain which you connect together on your PCB, 3 pins for the source which you connect together on your PCB and of course 1 gate pin. It's got the extra pins so it can deal with the current required. Other than that it's not any different from any other high current MOSFET to implement it on a board. Just make sure your PCB footprint and connection to it is correct so your device can cope with the current and also dissipating the heat generated. It'll use the PCB as part of the thermal dissipation so you may need additional copper within the board to take the heat away.

Best Regards,

Rachael
I have a weakness for Test Equipment so can often be found having a TEA break (http://www.eevblog.com/forum/chat/test-equipment-anonymous-(tea)-group-therapy-thread/)
 

Online MagicSmoker

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Re: regarding mosfet selection
« Reply #2 on: February 25, 2017, 05:27:27 AM »
Attached is a picture of my library entry for a similar package (Power-SO8).

Basically, you just need to use the "Connect"* command to assign the same pin on your MOSFET symbol (e.g. - D or S) to multiple pads on your package. Typically these style packages use three pins for the Source, four pins + exposed pad for the Drain, and one pin for the Gate.

* - more specifically, use "Connect" to assign the pin (ie - symbol) to the first of several pads (ie - package), then use "Append" to assign additional pads to the same pin as necessary.
« Last Edit: February 25, 2017, 10:40:42 AM by MagicSmoker »
 
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Offline msrinivasan1995

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Re: regarding mosfet selection
« Reply #3 on: February 25, 2017, 10:26:51 PM »
@rachel Ya , but I need is pictorial representation of how to connect or connected Mosfet which might be useful.
« Last Edit: February 25, 2017, 10:41:01 PM by msrinivasan1995 »
 

Offline msrinivasan1995

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Re: regarding mosfet selection
« Reply #4 on: February 25, 2017, 10:41:53 PM »
@magic smoker: Thank you, I will try it out
 

Offline technotronix

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Re: regarding mosfet selection
« Reply #5 on: March 07, 2017, 11:31:03 PM »
Have you tried with "Connect " command? This is work for me.
 

Offline msrinivasan1995

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Re: regarding mosfet selection
« Reply #6 on: March 15, 2017, 07:04:05 PM »
 
Have you tried with "Connect " command? This is work for me.
No i havent yet, i will try it
 

Offline richardlawson1489

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Re: regarding mosfet selection
« Reply #7 on: March 17, 2017, 09:11:49 PM »
Is there any option except "Connect" command? It worked for me but just want to know if any.
Thanks.
 

Online MagicSmoker

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Re: regarding mosfet selection
« Reply #8 on: March 17, 2017, 11:46:24 PM »
Is there any option except "Connect" command? It worked for me but just want to know if any.
Thanks.

Yes, you can put multiple pins on the symbol with nearly identical names. For example, [email protected], [email protected] for source pins, [email protected], [email protected] for drain pins, etc. Then connect each of those pins (symbol) to individual pads (package) when making the device. That is how we had to do it in the bad old days before the "Append" command was added, and it was a terrible kludge.

See attached picture for an example:



 


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