Replacement for HexSense FETSs

[Roger Hamlett]

Hi,
In the past, for some switching assemblies, I have on occasion taken
advantage of the IR HexSense FET's. Big advantages at moderate currents of
not needing an external sense resistor, at the 'cost' of needing an op-amp
to generate a reasonably accurate current sense result, some drift on the
high current units, and care needed in the software to 'tweak' for
temperature effects. Typically using the IRCP250, at perhaps 20A.
Now looking at redesigning a board I made some time ago, using these, and
find that they are shown as 'Divested', by IR. They are available at
present, but are obviously not the way to go for a new design.
I found myself wondering what is being used to replace these?....

Best Wishes

 

[Ray King]

Roger,
The hex since can be replaced by using the standard IRFP250 and a parallel
fet of higher voltage such as the IRFU420 with a 100 ohm resistor in the
source. Connect both drains together and connect both gates together. The
current signal is taken at the connection of the 100 ohm resistor and
IRFU420. The other end of the 100 ohm resistor is connected to the source of
the IRFP250. Also the fancy negative supply is not needed with this
connection because there is no concern about the signal current being
diverted in the silicon of the IRCP250. It also is more accurate with no
distortion at higher currents.
Ray


"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote in message
news:RdC4i.479$qD.361@newsfe6-win.ntli.net...

Hi,
In the past, for some switching assemblies, I have on occasion taken
advantage of the IR HexSense FET's. Big advantages at moderate currents of
not needing an external sense resistor, at the 'cost' of needing an op-amp
to generate a reasonably accurate current sense result, some drift on the
high current units, and care needed in the software to 'tweak' for
temperature effects. Typically using the IRCP250, at perhaps 20A.
Now looking at redesigning a board I made some time ago, using these, and
find that they are shown as 'Divested', by IR. They are available at
present, but are obviously not the way to go for a new design.
I found myself wondering what is being used to replace these?....

Best Wishes

 

[Roger Hamlett]

"Ray King" <rayjking@bellsouth.net> wrote in message
news:NFM4i.13583$KC4.6592@bignews6.bellsouth.net...

Roger,
The hex since can be replaced by using the standard IRFP250 and a
parallel fet of higher voltage such as the IRFU420 with a 100 ohm
resistor in the source. Connect both drains together and connect both
gates together. The current signal is taken at the connection of the 100
ohm resistor and IRFU420. The other end of the 100 ohm resistor is
connected to the source of the IRFP250. Also the fancy negative supply
is not needed with this connection because there is no concern about the
signal current being diverted in the silicon of the IRCP250. It also is
more accurate with no distortion at higher currents.
Ray
Thanks.

What suprises me, is that nobody seems to integrate such a solution
though, the 'dual fet' solution, will be rather bulkier (there are already
eight FET's along the heatsink, and while only four need current sensing,
it may get a bit 'tight'...
Have to find something other than the IRFU420 though. These too are
'divested'.
Oh well, a 'redesigning I will go'!.

Best Wishes

"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote in message
news:RdC4i.479$qD.361@newsfe6-win.ntli.net...
Hi,
In the past, for some switching assemblies, I have on occasion taken
advantage of the IR HexSense FET's. Big advantages at moderate currents
of not needing an external sense resistor, at the 'cost' of needing an
op-amp to generate a reasonably accurate current sense result, some
drift on the high current units, and care needed in the software to
'tweak' for temperature effects. Typically using the IRCP250, at
perhaps 20A.
Now looking at redesigning a board I made some time ago, using these,
and find that they are shown as 'Divested', by IR. They are available
at present, but are obviously not the way to go for a new design.
I found myself wondering what is being used to replace these?....

Best Wishes

 

[Gary Reichlinger]

On Wed, 23 May 2007 11:11:09 GMT, "Roger Hamlett"
<rogerspamignored@ttelmah.demon.co.uk> wrote:

Have to find something other than the IRFU420 though. These too are
'divested'.

I do not know the specific situation with this part, but just the
fact that it is "divested" does not necessarily mean that you will not
be able to get it in the future. Semiconductor companies have been
selling product lines and splitting companies in the last few years.
National Semiconductor, Motorola, HP, and others have done this over
the last few years. It is just a matter of whether whoever ends up
with the rights to your part chooses to produce it. I have been in
several situations where I thought a key part was not going to be
available due to this practice, but so far I have always been able to
find it from some successor or partner of the original. (I am watching
this particular situation myself as I use a number of IR parts.)

 

[Roger Hamlett]

"Gary Reichlinger" <reichln@navix.net> wrote in message
news:1nh853ln9tqbdanghv268t0kul160lbbac@4ax.com...

On Wed, 23 May 2007 11:11:09 GMT, "Roger Hamlett"
rogerspamignored@ttelmah.demon.co.uk> wrote:

Have to find something other than the IRFU420 though. These too are
'divested'.

I do not know the specific situation with this part, but just the
fact that it is "divested" does not necessarily mean that you will not
be able to get it in the future. Semiconductor companies have been
selling product lines and splitting companies in the last few years.
National Semiconductor, Motorola, HP, and others have done this over
the last few years. It is just a matter of whether whoever ends up
with the rights to your part chooses to produce it. I have been in
several situations where I thought a key part was not going to be
available due to this practice, but so far I have always been able to
find it from some successor or partner of the original. (I am watching
this particular situation myself as I use a number of IR parts.)
OK. Yes, I understand this practice (met it a lot, with TI parts in the

past). The problem (of course), is that you have to 'assume the worst',
unless the new manufacturer is already in place...

Best Wishes