Using Smart High-Side Power Switches as a battery switch + current sensor + protection

Hi guys,

The Smart MOSFETs are now really smart enough to use them in such applications as RC High Current switches. More, they have a current sensing output, which could be used for current sensing instead of commonly used Schunt+IC .

An example for such a device is BTS50015 - BTS50015-1TAA-Data-Sheet-11-Infineon.pdf

The very low Rds of less than 1.5mOhm and 3.3-5V drive voltage capabilities make it a nice device for further researches. The ICs could be also connected in parallel for higher currents.

Here is a typical current sensing diagram from IS pin:

and a typical application:

I'm going to design some prototypes based on BTS50015 and BTS555 and after testing them I'll post the results.

Enjoy and have fun!

Nick

Views: 4075

Comment by John Rambo on August 12, 2012 at 1:06am

$20 for BTS555 price at farnell? A good latching relay costs $10, or, alternatively - one could get a a handful of premium logic level MOSFETS.

How is this-one better?

Comment by Nick Arsov on August 12, 2012 at 2:49am

Hi John,

Correction....you can find it for less than EUR 5.60. More you'll not obtain a current sensing function from a latching relay. More, using a high current relay, you'll have at least 50g load in the plane.

Finally, as I said, this device is a basis for future developments as such devices have a huge potential.

Comment by John Rambo on August 12, 2012 at 6:17am

for $7 that's a fine device.

I've been looking for this kind of function for two weeks and ended up with ACS712 for the current sensing together with MTP3055VL MOSFETS for a 5V controlled switching. Full circuit came to cost just above $6 with a weight close to that of a small relay, which I don't like.

Comment by Nick Arsov on August 12, 2012 at 7:03am

Yes, true...really fine devices with a huge potential. More, it has a excellent protection functions. Take a look at the datasheets for overcurrent and reverse polarity protection. I'm sure there are also alternative devices from International Rectifier for example and some other manufacturers.

Comment by Richard on August 12, 2012 at 7:20am

@John - there are some much smaller logic-level N-Channel MOSFETs with much higher current capacities.

Look at some of the SMT packages - TO-252, D-PAK and I-PAK are just as easy to solder as TO-220.
They are probably cheaper as well - similar (or better) MOSFETs in DPAK come in well below 50 cents.

The two main advantages I see with the BTS50015 is the built-in shunt resistor and high-side driver.
The rest is just protecting the switching device, and you only really need that if the switching device is expensive...

Comment by Nick Arsov on August 12, 2012 at 8:07am

Hi Richard,

Just an additional small explanation - BTS50015/BTS555 do not use a built-in shunt resistor which dissipates heat, but a sense FET which is in the main FET structure. The sense cells pass only a small fraction of the total load current in proportion to the ratio of their areas. This ratio is typically from 500:1 to 10000:1

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