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'[EE] 3.6V logic to 15V'
2008\11\02@065916 by Richard Crossley

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Hi,

Been a while since I had to get my hands dirty and do any electronics design
so hopefully this will have an obvious answer.

I have three lines of 3.6V logic that I need to translate to around 15V
levels, two of which also need to drive high voltage FETs so they really
need to be able to both sink and source to overcome the gate capacitance and
achieve reasonable (sub microsecond) switching times (I know 15V drive for
the FET is 'overkill' but there is a lot of legacy CMOS logic in the
system). The board area is very pushed for size so I was hoping there would
be some monolithic interface circuit that could achieve this rather than
discrete components.

Any suggestions?

Cheers,

Richard.  


2008\11\02@074703 by peter green

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Richard Crossley wrote:
> Hi,
>
> Been a while since I had to get my hands dirty and do any electronics design
> so hopefully this will have an obvious answer.
>
> I have three lines of 3.6V logic that I need to translate to around 15V
> levels, two of which also need to drive high voltage FETs so they really
> need to be able to both sink and source to overcome the gate capacitance and
> achieve reasonable (sub microsecond) switching times (I know 15V drive for
> the FET is 'overkill' but there is a lot of legacy CMOS logic in the
> system). The board area is very pushed for size so I was hoping there would
> be some monolithic interface circuit that could achieve this rather than
> discrete components.
If you have a 5V supply availible and the 3.6V logic can supply
sufficiant current then a 74LS06 or 74LS07 (the only difference is one
is inverting the other isn't) running on 5V and with a pullup to 15V on
the outputs would do nicely for getting the levels to 15V.

As for the FET drive your best option is probablly a 15V CMOS buffer.


2008\11\02@094921 by Richard Crossley

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No 5V supply, just 3.6V and 15V.

A push-pull output would be way preferable to an open collector output to
get the FETs switching at a good speed, I'm really looking for a single chip
solution if at all possible.

Cheers,

Richard.

> {Original Message removed}

2008\11\02@104439 by Isaac Marino Bavaresco

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Richard Crossley escreveu:
> No 5V supply, just 3.6V and 15V.
>
> A push-pull output would be way preferable to an open collector output to
> get the FETs switching at a good speed, I'm really looking for a single chip
> solution if at all possible.
>
> Cheers,
>
> Richard.
>  
Try searching "mosfet driver" at http://www.digikey.com.
In the results page select "MOSFET, IGBT Drivers (3,555 items)
<http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556427;keywords=mosfet%20driver>"

Regards,

Isaac
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2008\11\02@111615 by Bob Blick

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Hi Richard,

I use the TC4469. It is meant for exactly your type of application.

Cheerful regards,

Bob

Richard Crossley wrote:
{Quote hidden}

2008\11\02@112427 by Isaac Marino Bavaresco

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Richard Crossley escreveu:
> No 5V supply, just 3.6V and 15V.
>
> A push-pull output would be way preferable to an open collector output to
> get the FETs switching at a good speed, I'm really looking for a single chip
> solution if at all possible.
>
> Cheers,
>
> Richard.
>  
Perhaps you could use one of these: L9380 from STM (Three channels,
Digikey L9380-ND) or LMD18400 from National Semiconductor (Four
channels, Digikey LMD18400N-ND).

Best regards,

Isaac
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2008\11\02@115844 by Danny Miller

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How big are these FETs?  Are they just logic inputs or real drivers?  
These aren't drivers that must switch simultaneously, are they?

There are drivers which are simply buffers/inverters to go from say 3.3v
to 15v.  Microchip makes a bunch.

There are logic-level FETs which can switch just fine with only 3.6v.  
Some can switch many amps.  That might be something to look into, simply
replacing what you're driving with something that doesn't need its own
15v gate driver.

Danny

Richard Crossley wrote:
{Quote hidden}

>> {Original Message removed}

2008\11\02@123103 by Richard Crossley

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The TC446X series looks like the way to go.

Shame it's got the input logic rather than 6 buffers or a smaller package
which would then have been perfect...  

Thanks to everyone for your suggestions.

Richard.





> {Original Message removed}

2008\11\02@145723 by Martin K

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Richard Crossley wrote:
> The TC446X series looks like the way to go.
>
> Shame it's got the input logic rather than 6 buffers or a smaller package
> which would then have been perfect...  
>
> Thanks to everyone for your suggestions.
>
> Richard.
>
>
>  


If you want straight buffers with no logic try the MIC4427:
<http://www.micrel.com/_PDF/mic4426.pdf>
Or something similar. There are dozens of these types of chips.

-
Martin K

2008\11\03@221320 by Mohit (Lists)

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> I use the TC4469. It is meant for exactly your type of application.
Unfortunately these work only down to 4.5V.


Bob Blick wrote:
{Quote hidden}

2008\11\03@232408 by Bob Blick

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He's using them at 15 volts. The 4.5V minimum spec you are reading is
for the output side, not the logic side. There is no logic supply on
them! This is what they are meant to do. Take another look at the datasheet.

Cheerful regards,

Bob

Mohit (Lists) wrote:
>  > I use the TC4469. It is meant for exactly your type of application.
> Unfortunately these work only down to 4.5V.

2008\11\03@234411 by Mohit (Lists)

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True, the DS says 2.4V as minimum high input voltage. Sorry!

Mohit Mahajan.

Bob Blick wrote:
{Quote hidden}

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