LM5069: Is there a similar part to the LM5069 with Automotive grade?

Hi Javier,

Welcome to E2E!

Please look at LM74800-Q1, Figure 13 in https://www.ti.com/lit/an/slvaes2/slvaes2.pdf for implementation and let us know if there are further questions

Best Regards, Rakesh

Hello, Rakesh

Thanks a lot for the information you shared. I liked that approach. However, I'm a little concerned about the power dissipation. For sensing current I was thinking of using a hall effect sensor because I didn't know about the existence of the INA302 until you pointed it out. 

Do you think that sensing up to 40A could be an issue in terms of excessive heat? My footprint should be as small as possible. 

Kind regards!

Hi Javier,

There are multiple amplifier gain options available in INA302. I think, selecting INA30xA3 allows using lower sense resistor to minimize the power dissipation.

I am forwarding the thread to INA302 team so that you will get more information and needed support on how to configure the values of INA302.

Hello, Rakesh

Thanks for the follow-up. While I define if I go with a hall-effect current sensor instead of the INA3x. Could you please clarify if it is possible to have the "Unsuppressed Load Dump Protection" (Figure 10) in combination with "Reverse Battery Protection" (Figure 13) by adding an LM74610-Q1 or another configuration?

Something similar to TIDA-01167

I found another post in which the transient protection + reverse polarity were required and you suggested the use of the LM74800, but I didn't understood if there is something else needed to have both features.

Kind regads!

Javier

Rakesh,

The answer on the heat dissipation question comes down to "how much heat is acceptable?" 

Using Rakesh's recommendation, if you were to use the A3 variant of the device, this would provide a gain of 100. Assuming you use a Vs of 5V, this means that in the ideal sense the maximum sense voltage that could be sensed at the input terminals to avoid saturation would be 50mV, and aligning that to your planned measurable maximum of 40A, you would then need a 1.25mΩ shunt to achieve this. Let's choose a real value of 1mΩ for the shunt, this would mean that your full scale output would be .001*40*100 = 4V, and the heat dissipated across the shunt in this condition would be .001*40*40= 1.6W. Is that an amount of heat you would be able to control?

Also, what measurement do you need to make on the lower end? Like all amplifiers, INA302 has a swing to GND limitation, which means that in single supply configuration, it will not be able to truly measure down to 0A. Is this something that is needed in your system?

Hello, Carolous

Thanks a lot for your recommendations!

Today, I talked with the customer in order to clarify some doubts, and it comes out that the requirement is for 3 channels with up to 40A +/-15% each, so the maximum current in the power bus could be 138A.

So, with that been said and using your suggestions my new configuration would be around the INA302A3 (gain of 100) with a 3.3V microcontroller.

The prototype will contain several power modules, so reducing the heat of each individual module is a must. For that reason, I'm planning to use a 0.1 mOhm resistor.

The full scale output would be => (0.0001 * 138 * 100) + 1.65V =  3.03V; and the max heat would be=> 0.0001 * 138 * 138 = 1.9W (If possible I would like to parallel two 0.1 mOhm resistors, so the heat could under 1W)

The best part I found was the WSLP3921L1000FEA (0.1 mOhm 1% 9W), which is extremely over-spec for the power dissipation is required, however, I neither found a cheaper nor smaller alternative.

I'm aware that using such a small resistor the error would be very high, at least 10% with a load of 15A, but to be honest the I only care about having a ~2% error when the load is higher than 100A.

What do you think? Am I missing something?