Received: by 10.59.1.102 with SMTP id bf6mr2722381ved.21.1349464498801;
Fri, 05 Oct 2012 12:14:58 -0700 (PDT)
X-BeenThere: nycresistormicrocontrollers@googlegroups.com
Received: by 10.52.89.80 with SMTP id bm16ls3459851vdb.9.gmail; Fri, 05 Oct
2012 12:14:54 -0700 (PDT)
Received: by 10.52.91.168 with SMTP id cf8mr1904111vdb.6.1349464494905;
Fri, 05 Oct 2012 12:14:54 -0700 (PDT)
Date: Fri, 5 Oct 2012 12:14:53 -0700 (PDT)
From: Bill French <william.fre...@gmail.com>
To: nycresistormicrocontrollers@googlegroups.com
Cc: dan...@verizon.net
Message-Id: <7abc2f28-dfcd-4be6-8058-289fe78cec23@googlegroups.com>
In-Reply-To: <506EE3A9.2030708@verizon.net>
References: <CAD8=kzUnC4d1TW5Sg8L7HwEfhbx6YA1U6rtWwS77TPrq3tPNtw@mail.gmail.com>
<506EE3A9.2030708@verizon.net>
Subject: Re: [NYCR:Microcontrollers] Paralleling mosfets vs. 1 big mosfet
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="----=_Part_161_18129808.1349464493781"
------=_Part_161_18129808.1349464493781
Content-Type: multipart/alternative;
boundary="----=_Part_162_33455869.1349464493781"
------=_Part_162_33455869.1349464493781
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Awesome, thank you .. any opinions on mosfet driver ics? I've been looking
at the Allegro A3941 (full bridge) and A3946 (half bridge) as they seem to
solve a lot of the things that confuse me, like "synchronous rectification"
and "charge pumping".
On Friday, October 5, 2012 9:42:17 AM UTC-4, Dan Lavin wrote:
> Unlike bipolar transistors, mosfets can be paralleled. Because Rds goes
> up with increasing temperature mosfets automatically balance current
> among them themselves. It is my understanding that power mosfets are
> actually constructed of paralleled internal arrays.
>
> As for one large vs multiple smaller mosfets, economic rather than
> technical considerations predominate. There is are tradeoffs of board
> space, heat sink requirements, and component cost to be considered. At
> higher frequencies and larger sizes gate capacitance is an issue to be
> considered as well. Large gate capacitance means a larger gate resistor
> is required to keep inrush current within limits and that means slower
> turn on times. Specs may differ between one large and several small
> mosfets
>
> When you look at motor controllers, you may be seeing H-bridges rather
> than paralleled mosfets as an H-bridge requires 4 mosfets. Check.
>
> Generally, to control a mosfet from an arduino, select one with logic
> level gate drive and use a small resistor between the arduino and the
> mosfet gate. Calculate the resistor value to keep the gate capacitor
> current inrush within the limit the arduino can source or sink, but it
> never needs to be more than about 100ohms
>
>
> On 10/5/2012 9:05 AM, Bill French wrote:
> > Hello, i'm trying to learn about mosfets for motor control with an
> > arduino, and my google searching is coming up a little short.
> >
> > Are there technical pros/cons to using say 4 x 20 amp mosfets vs. 1 x
> > 80 amp mosfet?
> >
> > What are the general thoughts on the matter? Seems most motor
> > controllers parallel their mosfets but maybe it's just a cost thing?
> > Thanks!
> > --
> > You received this message because you are subscribed to the Google
> > Groups "NYCResistor:Microcontrollers" group.
> > To post to this group, send email to
> > nycresistormi...@googlegroups.com <javascript:>.
> > To unsubscribe from this group, send email to
> > nycresistormicrocontrollers+unsubscribe@googlegroups.com <javascript:>.
> > For more options, visit this group at
> > http://groups.google.com/group/nycresistormicrocontrollers?hl=en.
>
>
------=_Part_162_33455869.1349464493781
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: 7bit
Awesome, thank you .. any opinions on mosfet driver ics? I've been looking at the Allegro A3941 (full bridge) and A3946 (half bridge) as they seem to solve a lot of the things that confuse me, like "synchronous rectification" and "charge pumping".<div><br></div><div>On Friday, October 5, 2012 9:42:17 AM UTC-4, Dan Lavin wrote:<br><blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">Unlike bipolar transistors, mosfets can be paralleled. Because Rds goes
<br>up with increasing temperature mosfets automatically balance current
<br>among them themselves. It is my understanding that power mosfets are
<br>actually constructed of paralleled internal arrays.
<br>
<br>As for one large vs multiple smaller mosfets, economic rather than
<br>technical considerations predominate. There is are tradeoffs of board
<br>space, heat sink requirements, and component cost to be considered. At
<br>higher frequencies and larger sizes gate capacitance is an issue to be
<br>considered as well. Large gate capacitance means a larger gate resistor
<br>is required to keep inrush current within limits and that means slower
<br>turn on times. Specs may differ between one large and several small mosfets
<br>
<br>When you look at motor controllers, you may be seeing H-bridges rather
<br>than paralleled mosfets as an H-bridge requires 4 mosfets. Check.
<br>
<br>Generally, to control a mosfet from an arduino, select one with logic
<br>level gate drive and use a small resistor between the arduino and the
<br>mosfet gate. Calculate the resistor value to keep the gate capacitor
<br>current inrush within the limit the arduino can source or sink, but it
<br>never needs to be more than about 100ohms
<br>
<br>
<br>On 10/5/2012 9:05 AM, Bill French wrote:
<br>> Hello, i'm trying to learn about mosfets for motor control with an
<br>> arduino, and my google searching is coming up a little short.
<br>>
<br>> Are there technical pros/cons to using say 4 x 20 amp mosfets vs. 1 x
<br>> 80 amp mosfet?
<br>>
<br>> What are the general thoughts on the matter? Seems most motor
<br>> controllers parallel their mosfets but maybe it's just a cost thing?
<br>> Thanks!
<br>> --
<br>> You received this message because you are subscribed to the Google
<br>> Groups "NYCResistor:Microcontrollers" group.
<br>> To post to this group, send email to
<br>> <a href="javascript:" target="_blank" gdf-obfuscated-mailto="sxGQIsEPZY0J">nycresistormi...@<wbr>googlegroups.com</a>.
<br>> To unsubscribe from this group, send email to
<br>> <a href="javascript:" target="_blank" gdf-obfuscated-mailto="sxGQIsEPZY0J">nycresistormicrocontrollers+<wbr>unsubscribe@googlegroups.com</a>.
<br>> For more options, visit this group at
<br>> <a href="http://groups.google.com/group/nycresistormicrocontrollers?hl=en" target="_blank">http://groups.google.com/<wbr>group/<wbr>nycresistormicrocontrollers?<wbr>hl=en</a>.
<br>
<br></blockquote></div>
------=_Part_162_33455869.1349464493781--
------=_Part_161_18129808.1349464493781--
Message from discussion Paralleling mosfets vs. 1 big mosfet
| Create a group - Google Groups - Google Home - Terms of Service - Privacy Policy |
| ©2013 Google |