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[Reply #30 on:]

Are defiantly wrong ive just gone through all my 20amp and 30amp chips and measured this resistance
results as follows, these were measured on the pins nothing attached to them on ip+ (pins 1 and 2) and ip- (pins 3 and 4).

acs 712 20a  total 6 ics,  all 0.3 ohms
acs 712 30a  total 13 ics  all 0.3 ohms

maby the figure they quote in their chart has a typo (mΩ) sould be just (Ω)

they do mention that the data was made using theAllegro ASEK712 demo board maby this resistance comes from extra circuitry there maby? but looking at it cant see any components that would suggest this

be really great if someone else could also confirm this resistance as well

Are you aware of how difficult it is to accurately measure resistance values down to the milliohm value? It usually takes using a 4 wire Kelvin set-up with a constant current sent through the unknown resistance and then measuring the resulting voltage drop across the unknown resistance. So describe your measurement method.

Lefty

[Reply #31 on:]

ok im stumped there, will look up 4 wire Kelvin set-up, thanks lefty.

ok i understand now thanks for pointing that out lefty

on a more practacle note ran my acs 712 30amp version, loaded it up to 10amps  ran constant for 5 mins, then checked it for its temp,  there was absolutely no heat in the ic casing what so ever.

according to the chart id be getting 80 ish dec C, in the chart it mentions Die temperature whatever this is? maby it the core of the ic itself maby? really not sure, but i didnt notice any heat generated at all @ 10 Amps, be nice to know what this die temp is though, i often hear case temp or package temp, but never die temp.

[Reply #32 on:]

For all I know, this chip puts up a lot less resistance than the manufacturer warrants in their documentation. And 10A through the 30A version may be perfectly safe, generating no heat in your application, etc. I am not criticizing your use of this chip. I was merely constrained by a design that requires high accuracy, low insertion losses, and the ability to withstand long duration exposure to high currents.

This sensor design with its SO8 frame and a mere two leads each carrying that current gave me the willies. That does not mean it doesn't work. I simply wanted something with more meat and some other attributes.

Please also note how the Allegro eval board offers a wide land for the leads going to the sensor and very heavy-duty connecting posts. It also features double-sided high-voltage PCB traces and 'stitched' construction. In other words, Allegro is using the copper on both sides of the board for the power signal and the conductors are thoroughly bonded to each other using lots and lots of vias to reduce insertion losses and improve thermal heat dissipation from the chip.

I am not convinced that many of the commercially-available boards out there go to the same lengths to ensure a wide, thick path or use the same extra-heavy copper trace thickness (2oz copper is uncommonly used, costs extra) as the Allegro board. Just something to keep in mind as you source your gear. Relying on conductors attached to the terminals to dissipate heat (as some design apparently expect to) seems like bad engineering practice.

On the other hand, if the chip stays super cool no matter what currents are being passed, then so much the better for you.

[Reply #33 on:]

I wouldn't recommend using Polou's board for anything above 50V - the missing isolation on the board is not too clever.

Running 230V on those pads would be very dangerous

// Per.

[Reply #34 on:]

There are a couple of designs out there that I find odd. This one, features no on-board caps and filters, a tiny land, etc. The adjustable Sparkfun board features a tiny load path and a giant nearby GND path nearby. I don't get it for safety reasons. The pololu board at least features some serious high-voltage lands though the distance to the low-voltage components seems questionable.

[Reply #35 on:]

yes i agree those designs are poor, not sure if those tracks are man enough for their intended currents tough, it took me about 6 attempts to get to this this design, i did a few versions where i had ground fill didnt work well, either. not a good idea to place tracks under the ic either, you have to isolate the pins either side.

the current path pins are as close as possible to the connector as possible and i then fill that track with solder from the connector to the 2 pins both sides to be sure  

[Reply #36 on:]

Hey guys, sorry for digging up this old post. I am making the PCB right now and I am wondering what is the purpose of the 0.1uF cap.

Let say I am going to include 10 ACS714 on a single board. According to the data sheet, a 0.1uF cap is suppose to be connected from VCC to GND. Can I just use one cap for all the ACS714? Should it be 0.1uF or 1uF? Thank you so much!

[Reply #37 on:]

Hey guys, sorry for digging up this old post. I am making the PCB right now and I am wondering what is the purpose of the 0.1uF cap.

Let say I am going to include 10 ACS714 on a single board. According to the data sheet, a 0.1uF cap is suppose to be connected from VCC to GND. Can I just use one cap for all the ACS714? Should it be 0.1uF or 1uF? Thank you so much!

It's the typical .1ufd bypass chip that all ICs should have mounted as close to each IC as possible. Don't try to skimp or combine into one or few caps.

Lefty

[Reply #38 on:]

Got it, thanks!