switch selection

[Michael]

I need to find a switch that is capable of withstanding 400-500V and
has lowest possible leakage, preferably way under 1uA. The load
current is from nanoamps to tens of microamps. Relays are way to big
and I am not sure how the contacts behave if load current is way too
low.
MOSFET - ? I haven't been able to find one with low enough leakage (I
am still looking).

The application: I need to be able to geta (low current) plus or minus
couple hundred (100...400, actually) volts bias from the same board. I
have two HV supplies, one of them needs to be disconnected.
Thank for suggestions
)

 

[HiggsField]

---
http://www.comus-intl.com/products/PS SIP HG reed.pdf

Take a look at the MVS4.

There are also lots of other HV low-leakage mercury wetted reed relays
out there.

JF

A little heavy for the currents described, but:

http://www.teledynerelays.com/industrial/s60dc40.asp

 

[Michael]

I've seen a few manufacturers lately who use "LF" instead of "DC" to
indicate the lower frequency limit of their parts, like RF switches
and mmics. That's more honest.

We used one Hittite part, an 8pstswitch, that absolutely screwed up
below about 80 MHz. The huge lettering at the top of the datasheet
said (envision huge letters) DC. When I complained about it, they told
me that I hadn't examined the S-param graphs closely enough.

Hey, it still does:

http://www.hittite.com/content/documents/data_sheet/hmc253qs24.pdf

John

Thanks for your help guys. This FTR-B3SB4.5Z thing seems to be very
attractive except height (have <5mm limit on one side of the board and
I have to check mechanical model for the other side).
Another thing that bugs me is "minimum switching load" of 10uA. What
if I need to switch less? Will I get some noise on contacts???
???What defines minimum switching current for mechanical contacts???

I found (picked) PVU414 (there are plenty of replacement, which is
important for our small volumes). 1uA max leakage is something I can
live with (I think)

 

[Michael]

---
Since he's hot switching 400V and the relay's spec'd at 220VDC max
(page 5 of the data sheet) he may run into life problems.

JF

I just checked "mechanicals". The height limits are: <5mm one side of
PCB and <2mm another side of PCB. Ooooops!
(

 

[Michael]

---
Check this out:

http://www.hamlin.com/specsheets/MARR-5.pdf

You'll need to get/wind a coil for it, but at 17AT you should have no
problem fitting it onto the 5mm side of the board.

What supply voltage do you have available to drive the coil?

And, BTW, can you rout a slot in the board and slip the relay into it
to get a few more mm of height that way?

JF

Winding a coil.... Grrrrr. I'd rather not get into it. I would
probably get yelled at by people who deal with CMs

...And, BTW, can you rout a slot

It's a very good idea.
BUT... The board is very tight as it is and cutting out 10x7mm hole
doesn't make me feel very good... I'll look into it, though.

 

[Michael]

---
Check this out:

http://www.hamlin.com/specsheets/MARR-5.pdf

You'll need to get/wind a coil for it, but at 17AT you should have no
problem fitting it onto the 5mm side of the board.

What supply voltage do you have available to drive the coil?

And, BTW, can you rout a slot in the board and slip the relay into it
to get a few more mm of height that way?

JF

One more comment. If I have zero cutout tolerance, I will have 0.5mm
of leads on each side to solder to. The relay has 0.2mm width
tolerance. This leaves me with 0.3mm. The leads have +...-0.3mm
tolerance. This leaves me with... nothing.
(