--===============0975773351== Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by pch.mit.edu id m55GMWLt026983 =20 =20 Some people from Fairchild stopped by this morning and showed me this opt= ocoupler based gate driver =20 http://www.fairchildsemi.com/ds/FO%2FFOD3180.pdf =20 a pretty good one, output 2A with rise and fall time within 80ns range. =20 I found another company that does this, called Avago, their opto products= look amazing. =20 http://www.avagotech.com/products/optocouplers_-_plastic/plastic_integrat= ed_gate_drive_optocoupler/ =20 For those who might do the same work in the future, I conclude that the o= nly chip that integrates the on-chip charge pump would be Linear Tech's d= river LT1336. > Date: Thu, 5 Jun 2008 10:43:07 -0400> From: shb7@cornell.edu> To: picli= st@mit.edu> Subject: Re: [EE]Would you show me a good gate driver chip fo= r 100% duty cycle?> > One very important thing to keep in mind here is th= at you must make> sure that you never get a Vgs higher than the max Vgs s= pec on the> high-side FETs.> > How fast do you need the high-side FETs to= turn on? If you don't need> very strong gate drive, I'd recommend just u= sing a photovoltaic> optocoupler (basically an LED and a solar cell in a = DIP package). Some> examples are the international rectifier parts starti= ng with PVI (for> example, PVI5033). These can turn the FET off quite fas= t but cannot> turn it on very fast (for example, a FET with 30nC of gate = charge> would take about 30 milliseconds to turn on with this device).> >= If you need very fast turn on, you could probably do what other> posters= suggested (putting one of these in parallel with the bootstrap> cap - yo= u would have to leave it turned on all th e time to keep the> cap charged).> > Sean> > > On Thu, Jun 5, 2008 at 8:= 14 AM, Gerhard Fiedler> wrote:> > gardenyu w= rote:> >> >> Besides, if I can have this additional power supply, how can= I turn on> >> this supply to charge the boostrap cap? I don't want anoth= er output from> >> microcontroller saying we want a full duty cycle, I ju= st want to turn> >> on the supply with the 100% PWM output, if it appears= . But, if PWM is> >> below 100%, it won't turn on. How can I realize that= ?> >> > One possibility is to have an (one) additional supply voltage tha= t is a bit> > higher than the highest gate voltage you need, switch it wi= th opto couplers> > and limit the gate voltage at each FET.> >> > Gerhard= > >> > --> > http://www.piclist.com PIC/SX FAQ & list archive> > View/cha= nge your membership options at> > http://mailman.mit.edu/mailman/listinfo= /piclist> >> -- > http://www.piclist.com PIC/SX FAQ & list archive> View/= change your membership options at> http:/ /mailman.mit.edu/mailman/listinfo/piclist _________________________________________________________________ =D3=C3=CA=D6=BB=FAMSN=C1=C4=CC=EC=D0=B4=D3=CA=BC=FE=BF=B4=BF=D5=BC=E4=A3=AC= =CE=DE=CF=DE=B9=B5=CD=A8=A3=AC=B7=D6=CF=ED=BE=AB=B2=CA=A3=A1 http://mobile.msn.com.cn/ --===============0975773351== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: 7bit -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --===============0975773351==--