I need a mosfet gate driver, to drive two n-fets in a half-bridge (totem pole) config, 5 volts nom in, with some sort of bootstrap for the upper fet gate. Switcher output will be around 2.5 volts at 5 amps, so the gate drives don't have to be monstrous. I've been working with LTC4442 on a breadboard, but it's really erratic. Sometimes it's beautiful, and sometimes the gate drive breaks up ugly. It's especially bad if Vcc gets much over 5 volts. I think the anti-shoot-through circuit is too smart or something. I don't have the paddle grounded, which could be part of the problem maybe. Maybe it wants that extra ground connection. It's hard to do that on a breadboard. But the ground pin doesn't look very noisy. Any suggested parts? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
gate driver
Started by ●November 12, 2014
Reply by ●November 12, 20142014-11-12
On 11/12/2014 2:39 PM, John Larkin wrote:> > > I need a mosfet gate driver, to drive two n-fets in a half-bridge > (totem pole) config, 5 volts nom in, with some sort of bootstrap for > the upper fet gate. Switcher output will be around 2.5 volts at 5 > amps, so the gate drives don't have to be monstrous. > > I've been working with LTC4442 on a breadboard, but it's really > erratic. Sometimes it's beautiful, and sometimes the gate drive breaks > up ugly. It's especially bad if Vcc gets much over 5 volts. I think > the anti-shoot-through circuit is too smart or something. > > I don't have the paddle grounded, which could be part of the problem > maybe. Maybe it wants that extra ground connection. It's hard to do > that on a breadboard. But the ground pin doesn't look very noisy. > > Any suggested parts? > >Hi, I am guessing the erratic behaviour you are noticing is related to the boost cap charge state. That IC needs to have PWM to charge up the boost cap for feeding the high side fet gate, if you leave the top fet on too long with a gate draining resistor that might discharge the cap before you turn the top fet off. I did a project with a related halfbridge fet driver IR2184(4) and noticed I had to use 99% max PWM otherwise 100% PWM wouldn't work for this bootstrap capacitor reason. cheers, Jamie
Reply by ●November 12, 20142014-11-12
On 13/11/14 09:39, John Larkin wrote:> > > I need a mosfet gate driver, to drive two n-fets in a half-bridge > (totem pole) config, 5 volts nom in, with some sort of bootstrap for > the upper fet gate. Switcher output will be around 2.5 volts at 5 > amps, so the gate drives don't have to be monstrous. > > I've been working with LTC4442 on a breadboard, but it's really > erratic. Sometimes it's beautiful, and sometimes the gate drive breaks > up ugly. It's especially bad if Vcc gets much over 5 volts. I think > the anti-shoot-through circuit is too smart or something. > > I don't have the paddle grounded, which could be part of the problem > maybe. Maybe it wants that extra ground connection. It's hard to do > that on a breadboard. But the ground pin doesn't look very noisy. > > Any suggested parts?HIP4081 perhaps? It's a full-bridge driver, but has independent control of both half-bridges. It'll make your high-side bias, control dead-time and prevent shoot-through.
Reply by ●November 13, 20142014-11-13
On Thu, 13 Nov 2014 14:50:44 +1100, Clifford Heath <no.spam@please.net> wrote:>On 13/11/14 09:39, John Larkin wrote: >> >> >> I need a mosfet gate driver, to drive two n-fets in a half-bridge >> (totem pole) config, 5 volts nom in, with some sort of bootstrap for >> the upper fet gate. Switcher output will be around 2.5 volts at 5 >> amps, so the gate drives don't have to be monstrous. >> >> I've been working with LTC4442 on a breadboard, but it's really >> erratic. Sometimes it's beautiful, and sometimes the gate drive breaks >> up ugly. It's especially bad if Vcc gets much over 5 volts. I think >> the anti-shoot-through circuit is too smart or something. >> >> I don't have the paddle grounded, which could be part of the problem >> maybe. Maybe it wants that extra ground connection. It's hard to do >> that on a breadboard. But the ground pin doesn't look very noisy. >> >> Any suggested parts? > >HIP4081 perhaps? It's a full-bridge driver, but has independent >control of both half-bridges. It'll make your high-side bias, >control dead-time and prevent shoot-through.Nice part, but it needs 8 volts, and I only have 5. Thanks -- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 14, 20142014-11-14
On Wed, 12 Nov 2014 14:39:36 -0800, John Larkin <jlarkin@highlandtechnology.com> wrote:> > >I need a mosfet gate driver, to drive two n-fets in a half-bridge >(totem pole) config, 5 volts nom in, with some sort of bootstrap for >the upper fet gate. Switcher output will be around 2.5 volts at 5 >amps, so the gate drives don't have to be monstrous. > >I've been working with LTC4442 on a breadboard, but it's really >erratic. Sometimes it's beautiful, and sometimes the gate drive breaks >up ugly. It's especially bad if Vcc gets much over 5 volts. I think >the anti-shoot-through circuit is too smart or something. > >I don't have the paddle grounded, which could be part of the problem >maybe. Maybe it wants that extra ground connection. It's hard to do >that on a breadboard. But the ground pin doesn't look very noisy. > >Any suggested parts?From the data sheet... GND (Pin 4, Exposed Pad Pin 9): Chip Ground. The exposed pad must be soldered to the PCB ground for electrical contact and for rated thermal performance. Maybe devise a spring clip to contact the back-side pad in your breadboard? ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●November 14, 20142014-11-14
On 11/12/2014 05:39 PM, John Larkin wrote:> > > I need a mosfet gate driver, to drive two n-fets in a half-bridge > (totem pole) config, 5 volts nom in, with some sort of bootstrap for > the upper fet gate. Switcher output will be around 2.5 volts at 5 > amps, so the gate drives don't have to be monstrous. > > I've been working with LTC4442 on a breadboard, but it's really > erratic. Sometimes it's beautiful, and sometimes the gate drive breaks > up ugly. It's especially bad if Vcc gets much over 5 volts. I think > the anti-shoot-through circuit is too smart or something. > > I don't have the paddle grounded, which could be part of the problem > maybe. Maybe it wants that extra ground connection. It's hard to do > that on a breadboard. But the ground pin doesn't look very noisy. > > Any suggested parts? > >I usually put a blob of solder on the pad, and another one on the board. Then I melt the board side with the iron lying almost flat, set the chip on top of the iron till both sides are melted, and pull the iron out. Usually works pretty well--it's how I heat-sink LM78xx regulators in breadboards. Not exactly a production-worthy technique, but I've never had one die yet. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●November 14, 20142014-11-14
With only 5 volts in, can't you roll your own? Small boost or charge capacitor supply to make a 15V rail and a capacitor coupled gate drive. (You need to be sure you don't have nasty transients on the 5V input Regards Klaus
Reply by ●November 14, 20142014-11-14
On Fri, 14 Nov 2014 13:52:55 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 11/12/2014 05:39 PM, John Larkin wrote: >> >> >> I need a mosfet gate driver, to drive two n-fets in a half-bridge >> (totem pole) config, 5 volts nom in, with some sort of bootstrap for >> the upper fet gate. Switcher output will be around 2.5 volts at 5 >> amps, so the gate drives don't have to be monstrous. >> >> I've been working with LTC4442 on a breadboard, but it's really >> erratic. Sometimes it's beautiful, and sometimes the gate drive breaks >> up ugly. It's especially bad if Vcc gets much over 5 volts. I think >> the anti-shoot-through circuit is too smart or something. >> >> I don't have the paddle grounded, which could be part of the problem >> maybe. Maybe it wants that extra ground connection. It's hard to do >> that on a breadboard. But the ground pin doesn't look very noisy. >> >> Any suggested parts? >> >> > >I usually put a blob of solder on the pad, and another one on the board. > Then I melt the board side with the iron lying almost flat, set the >chip on top of the iron till both sides are melted, and pull the iron >out. Usually works pretty well--it's how I heat-sink LM78xx regulators >in breadboards. Not exactly a production-worthy technique, but I've >never had one die yet. > >Cheers > >Phil HobbsBeen trying to find a picture, without success, of an over-top-dead-center clamp that I used in my Motorola days to press a flat pack down on a PCB to test it without soldering. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●November 14, 20142014-11-14
On Wednesday, November 12, 2014 5:39:44 PM UTC-5, John Larkin wrote:> I need a mosfet gate driver, to drive two n-fets in a half-bridge > (totem pole) config, 5 volts nom in, with some sort of bootstrap for > the upper fet gate. Switcher output will be around 2.5 volts at 5 > amps, so the gate drives don't have to be monstrous. > > I've been working with LTC4442 on a breadboard, but it's really > erratic. Sometimes it's beautiful, and sometimes the gate drive breaks > up ugly. It's especially bad if Vcc gets much over 5 volts. I think > the anti-shoot-through circuit is too smart or something. > > I don't have the paddle grounded, which could be part of the problem > maybe. Maybe it wants that extra ground connection. It's hard to do > that on a breadboard. But the ground pin doesn't look very noisy. > > Any suggested parts?Are the FETs extra large? This chip performance peaks at 3nF, and that's with everything laid out perfectly with low to nonexistent series inductance. The back GND pad floating could easily interfere with switching performance at its advertized speed.> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
Reply by ●November 14, 20142014-11-14
On 11/14/2014 11:37 AM, Jim Thompson wrote:> On Fri, 14 Nov 2014 13:52:55 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 11/12/2014 05:39 PM, John Larkin wrote: >>> >>> >>> I need a mosfet gate driver, to drive two n-fets in a half-bridge<SNIP>> > Been trying to find a picture, without success, of an > over-top-dead-center clamp that I used in my Motorola days to press a > flat pack down on a PCB to test it without soldering. > > ...Jim Thompson >Take a look at Carr-Lane website, toggle clamps. -bill
