tiny dc/dc

MSL 3 so buy them in onesies and twosies if you're going to prototype perhaps.. my experience is that chips with internal isolation barriers are very sensitive if they get waterlogged, not just reflow but even hot air or hand soldering may wreck them if they've sat out too long.

I asked our TI rep for the eval board and he sent me a long list of questions that I must answer first. Too much hassle, so I'll use a Murata part.

Potentially very nice part, thanks!

Cheers

Phil Hobbs

Why does it have such poor esd ratings? The ucc33421 is better, but not 15kv. Cheers

Right now I dodn't need kilovolts of isolation. I want to make a GaN totem-pole driver and want a floating power supply for the high side, but I want very low switching noise for low jitter on the rising edge.

I might try one of these with a bunch of added filtering. It might be better than some dc/dc that works in the 100 KHz sort of ballpark.

Or it might be much worse.

The obvious difference is the operating frequency. If you were particularly worried by 64MHz noise, the high frequency part might present a problem. With a particularly skilled designer, it might not.

Why not buy one and find out?

It doesn't actually have an ESD rating - spec only mentions the relevant standards and advises care in layout.

Those are isolation test voltages you`re looking at.

RL

I bet the gain bandwidth of a GaN FET in its linear range at high current is pretty impressive.

I’m using SiGe BJTs to speed up the edges of my TDR pulse generators. Driven from a 500-ps comparator edge, it’s fast enough to oscillate on the falling edge if the layout isn’t right. That’ll make really entertaining jitter.

Cheers 🍻

Phil Hobbs

One part that I like is the EPC2037, the tiny BGA thing. I think you have used it too.

Transconductance is about 1.5S and it's on hard by 3 volts on the gate. Capacitances are absurdly low compared to a silicon mosfet... reverse transfer is 0.1 pF.

But a little noise on the gate drive will surely jitter the output.

I never had much luck getting bipolars to make fast output edges, but I haven't tried SiGe.

That tiny EPC thing is rated for 100 volts and can conduct 2 amps!

I get about 30-40 ps falling edges, which are all that matter for TDR. The rising edges aren’t nearly as good, because I’m saturating the poor thing completely. It’s a 65 GHz transistor, though, so even an edge like that has room for a snivet.

Yup, a very nice part. I use it in my ultrafast temperature controller, which I call a thermal Faraday shield. 🛡️ (Details forthcoming when the patent gets filed.)

Cheers

Phil Hobbs

I use the 2037 and 2038 in the output stage of our DDG

I believe that. Did you get one for your bench?

Cheers

Phil Hobbs

Yes!

Did you get your old dead P400 repaired? Do you have two now?

People tell me that the old P400s have less jitter than the new P500. I suspect that dc/dc converter noise in the P500 output stage is the culprit, and the TI dc/dc might fix that.

I note that most have basic isolation, but a couple have reinforced isolation.

So, how long before Chinese fraudsters start relabeling the presumably cheaper basic isolation models as more expensive reinforced isolation parts?

Sylvia.

I guess Murata NXJ switches at a similar frequency!

-- Uwe Bonnes snipped-for-privacy@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt

--------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------

About 100 KHz.

What I need is a photovoltaic optocoupler with serious CTR. The ones I can get have CTRs like 0.5%. Power gain is better, but they make 8 or so volts and I only need 3.3.

I recall someone once making some optocouplers with serious power capability, but can't find them now.

A PV would sure be quiet.

Thanks!

And MPS MIE1Wxx?