Looking for low-side switch with crrent sensing

I need to make a heater circuit more intelligent. The existing design uses a low-side switch with with a simple logic feedback to check for proper operation. An objective is to replace that with a device that will provide a voltage output proportional to the heater current.

I have found a few high-side switches that will do the job and I am starting to lean that way.

Reply to
Richard Henry
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To monitor the current going to the heater, as he says below.

Does it matter in the context of the question?

Can you truly not think of any good reasons for wanting to monitor the heater current? Ah well chalk it up to either a lack of imagination or a lack of experience. How is the reason he wants to monitor the current relevant to the question?

I can't personally think of a clearer way to ask "does anyone know of a low-side switch with current monitoring?" Perhaps you could reprase it in a way that makes it clearer, or did you reply the way you did just to make yourself feel smart? 'Cause all you've done is make yourself look like a bit of a dope.

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Trevor Barton
Reply to
Trevor Barton

Ok, but to do exactly what?

The existing design uses

Some safety feature, perchance?

An objective is to replace that with a device that will provide

Not proportional to temperature? Just why do you need to know the current?

Don't mean to be rude here, but this is a great example of 'how not to ask a question'. Asking the right questions here will generally get you very good answers.

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Luhan Monat (luhanis 'at' yahoo 'dot' com)
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Reply to
Luhan Monat

Reply to
Ol' Duffer

IR website search engine doesn't return anything for "sensefet".

One of the parts I am looking at is the IR3312S. From the data sheet and appnote, it requires an external FET to translate the input signal from logic level, a slight disadvantage. A compensating advantage ( something I was not originally looking for) is that the feedback current resistor can be used to set the overcurrent limit.

uses

provide

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Reply to
Richard Henry

Why not just a big MOSFET with a small resistance in the source lead, plus a low-offset opamp?

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Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

What sort of current are you talking about ? Maximum voltage ? Philips, ST Electronics and International Rectifier has these sort of devices.

Regards Anton Erasmus

Reply to
Anton Erasmus

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Good Luck! Rich

Reply to
Rich Grise

I guess I'm dating myself... It appears they have changed the name to "hexsense", and their search engine isn't very useful. They make 5-leg TO-220 and TO-247 package devices, IRC730 for example. Download AN-959 from their archives for an overview.

Reply to
Ol' Duffer

Anyone figure out if this is an AC or a DC current sensing requirement ? What kind of Amps too ?

Makes a big difference how to constuct what is required !

Jay

Reply to
j.b. miller

I stand by my remarks. Like many things I've seen on this NG, it lacks some overall context for the questions being asked. At least, it honestly seemed that way to me. If I'm wrong here, well, thats the way things work here - after some back-and-forth bantering, some useful information usually emerges overall.

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Luhan Monat (luhanis 'at' yahoo 'dot' com)
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Reply to
Luhan Monat

Would it not be better to know whether the heater here is used to heat a fish tank or regulate blood temperature in a heart-lung machine?

I can *imagine* altogether tooooo many posibilities here. If this were a paying client asking the original question, I would certainly want to know exactly what the heater was part of. For liablility reasons for starters.

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Luhan Monat (luhanis 'at' yahoo 'dot' com)
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Reply to
Luhan Monat

Given the description I suspect Allegros devices are too large and probably too expensive but you may want to have a look.

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Then again maybe not, I see they go as low as 5A now.

Robert

Reply to
R Adsett

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