Can ESD protection (NUP4202) be used for longer overvoltage protection? - Page 1
Forum section: electronics / beginners

author: rve
author_rank: Newbie
timestamp: May 07, 2023, 06:09:57 pm
content: Hi,Can a TVS/ESD protection diode array such as a NUP4202 be used for overvoltage protection when someone connects a higher voltage (like 12 volt) to the input for a longer time?For example:If I permanently connect 12 volt to the scary side, will it survive and protect the safe side?I have some trouble finding information in the datasheet if this is allowed.Thanks.

author: srb1954
author_rank: Super Contributor
timestamp: May 07, 2023, 07:51:29 pm
content: Quote from: rve on May 07, 2023, 06:09:57 pmFundamentally, there is no reason why you couldn't use it in this mode provided you keep the average power dissipation within the limits of the chip and package. Unfortunately, the data sheet gives no information about the allowable average power dissipation so you might have to take some guesses about this, perhaps looking at other similar sized packages.With the circuit configuration you have shown the continuous clamping voltage will be largely determined by the 5V supply. If this can sink the excess current continuously then the NUP4202's internal Zener diode won't dissipate any power and the maximum clamping current will be the lesser of the continuous current rating of the clamp diodes or the 5V supply's ability to sink extra current. A warning - most voltage regulators are not too tolerant of the output pin having current injected into it and this could destroy the regulator if the output voltage is forced above the input voltage. Also, determining the continuous current rating of the clamp diodes will be difficult as no information is given in the data sheet about this.If you can tolerate the extra capacitance of an ordinary Zener diode it is a better option for clamping such lines. It will be much easier to determine the performance as the Zener diode data sheet will provide all the information necessary for prolonged or continuous clamping operation.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 07, 2023, 08:21:39 pm
content: Fine as long as thermal limits are respected, yes.200 ohms limits current to a couple 10s of mA.How much load is on 5V, is it enough to keep it from lifting? Will anything else get offended if it lifts up (to breakdown of the diode, ~7V typically)?Can the resistor be larger, or should it be low for other reasons (bandwidth, termination)?Note that outside-facing series resistors don't do anything for ESD (they're likely to arc over), but an inside (i.e. between TVS and IC) resistor limits current into the IC.Tim

author: JustMeHere
author_rank: Frequent Contributor
timestamp: May 07, 2023, 08:22:53 pm
content: Looks like the Zener regulator circuit just turned a little sideways.

author: Jeroen3
author_rank: Super Contributor
timestamp: May 08, 2023, 06:06:02 am
content: Clamping voltage of these diodes is somewhat high and wide, 8.5-12.5V, and it also injects current into the 5V rail.The package power of 250mW (typical SOT-363) is not that high either.I'd recommend finding another solution, what is the end goal of the circuit?

author: rve
author_rank: Newbie
timestamp: May 08, 2023, 07:14:32 am
content: The goal is to protect the input from accidentally connecting it to some higher voltage (within reason like 12V DC, not 230V AC) and some ESD protection with a minimal amount of parts. I was wondering whether the TVS diode array could be (mis)used for this as I could not find relevant information in the datasheet.There is some protection on the 5V rail to keep it from lifting, but not enough if all inputs are injecting current into the 5V rail.I think I'll just add a zener to ground after the resistor as mentioned by srb1954

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 08, 2023, 01:00:52 pm
content: Quote from: Jeroen3 on May 08, 2023, 06:06:02 amFor quick reference,https://www.onsemi.com/pdf/datasheet/nup4202w1-d.pdfBreakdown is 6V minimum (1mA), and while maximum isn't specified, a clamping voltage typ. 8.5V suggests it should be fairly tight (6-8V zener, perhaps?). If we assume the difference in max clamping is due to a fixed internal resistance, then 12.5V - ( (20V - 12.5V) * (5A / 8A) ) = 7.8V, which seems a reasonable guess. I would be shocked if the TVS were any worse tolerance than any other TVS.It is noteworthy that the TVS is directly accessible, so the measurements may not include Vf. Actually... none of these may? I would assume any with Note 5 are done at IO pins, not TVS direct. Which would mean most of them are TVS alone...sneaky!And nowhere is Vf specified, for small or large currents... it wouldn't matter if they gave IO clamping, and one would hope that's the case, but I have a very strong suspicion it isn't.For comparison, here's a similar device without the TVS directly accessible:https://www.onsemi.com/pdf/datasheet/cm1223-d.pdfCertainly not from the same family; not necessarily from the same era, or specified in the same way, or with the same intent; is still from SCI at least. If these datasheets would otherwise be written similarly, it does seem like they would've specified TVS clamping voltages if they could, and therefore the lack of any such figures indicates they're purely TVS ratings in the NUP-. Again we see no signal or peak clamping voltage limits -- typical only! (Curiously no specification on the Vp diode either, not even clamping voltage or capacitance; it could've been specified like another IO channel but without negative clamping, if they wanted to.)Interestingly they dropped the parameter glossary, which might suggest they aren't from similar eras / authors / writing styles, and that one shouldn't infer too hard about the difference in choice of parameters between these two sheets.This one,https://www.diodes.com/assets/Datasheets/D1213A-04S.pdfgives Vf in surprisingly great detail, but frustratingly, absolutely no hard clamping limits!This,https://www.bourns.com/docs/Product-Datasheets/CDSOT236-0504C.pdfdoes not give min/typ/max, but labels them, and I see a lot of maximums which is nice. Notes 1/4 and 2 strictly and unambiguously define TVS-only or IO channel clamping respectively. Theonlytypical parameter on here is ESD clamping voltage: perhaps they shy away from this, as it's so dependent on layout (stray inductance)?Presumably one could still assign a guard-banded maximum for the ESD clamping voltage (say 30, or 60V even?), given a well defined setup, but maybe that wouldn't be very useful either, as you can't assume the voltage range is due to element voltage drops, when it's actually due to strays and wave reflections instead; and readers might incorrectly assume it is device drop, leading to confusion. Alternately, one could specify a filter or median sampling method upon the measured waveform -- oh, or over a collection of waveforms -- in effect admitting that, yes, there's spiky junk on there, but it's not"real"and bear with us here, but "this" is the amount that can be reasonably attributed to the device, intrinsically. But maybe that too isn't ideal, for two reasons: 1. the complexity of this definition makes it not so useful in practice, and 2. it may be much easier to game, say by subtracting too greedily and removing all stray inductance from the waveform, not just PCB strays. (That is, subtracting out bondwire, pin and pad inductances.)Tim