Re: neat Hall sensor

On Sat, 04 Jan 2025 12:07:06 -0500, legg <legg@nospam.magma.ca> wrote:

On Fri, 03 Jan 2025 08:07:49 -0800, john larkin <JL@gct.com> wrote:
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On Fri, 03 Jan 2025 09:33:01 -0500, legg <legg@nospam.magma.ca> wrote:
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On Thu, 02 Jan 2025 08:09:16 -0800, john larkin <JL@gct.com> wrote:
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On Thu, 02 Jan 2025 09:05:03 -0500, legg <legg@nospam.magma.ca> wrote:
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On Tue, 31 Dec 2024 15:58:07 -0800, john larkin <jl@glen--canyon.com>
wrote:
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https://www.monolithicpower.com/en/mcs1802.html?srsltid=AfmBOoq2BNuYQ-Ef5ee9o7-gyHDqRkK_xS5TAKb-MgxtjZ6r71FItxXm
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Really nice, as compared to a shunt and an isolated ADC and all that
stuff. Reasonably accurate, especially above 20c.
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But they can't be serious about pushing 50 amps through an SO8
package. Or not for long.
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Their demo board thermal design is kinda silly.
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Demo board makes sense to me. Simplest thermal conductivity
test.

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They used 4 oz copper, hardly practical.

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?
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What's impractical about 4oz copper in a power circuit?
Are you saying it's not enough?

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I'm saying that you can't put any other reasonable parts on the board.
4 Oz is fine for a demo board, but not so good for a board with 0402
parts and FPGAs and anything that does anything but measure current.
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It would be interesting to get the eval board and actually push 50
amps through it.
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I see a lot of data sheets with absurd power and current ratings, like
a dpak rated for hundreds of amps and watts, with tiny footnote
somewhere that cautions about package or lead limits. IR started the
trend of specifying chip therortetical limits that can't be approached
in real life, and then everybody had to tag along.
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I'd say it was more than could be expected from a
simple demo board and is typical of higher current
layout in this neck of the woods, where power and
control circuits try not to share the same board or
board layer.

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Exactly.
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Also, using a part with a 50A full scale in a 25-30A
continuous rated circuit would be normal pactice,
where duty cycle, crest factor or pulse/surge are
anticipated under normal operating conditions.
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There are 'better' SMD packages available, if that is your
only concern. You seem to have found some.

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They could at least merged the high current pin pairs into big
paddles.

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Ends up looking like an automotive fuse link.
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It's a nice part. We're using the 10 amp version at up to 7.5 amps.
The 50 amp version is silly.

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Well, when you actually get around to using it (probably in a
relatively remote location) be sure to R/C the power and
data lines. R in series with source, C at receiving end.
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RL

That Monolithic Hall sensor is analog output. Zero current outputs
Vcc/2, and the sensitivity is ratiometric on Vcc. So one uses the same
rail for sensor Vcc and for the ADC reference. We'll autozero it every
powerup.

I'll RC filter a bit, right at the ADC input. Most ADCs kick out some
charge when they sample, and that freaks out a lot of analog parts.

I'll have eight Hall sensors on a board, about like this one:

https://highlandtechnology.com/Product/P945