INA216: Output driving capability

Hello user463911,

Thanks for considering to use Texas Instruments. We do not provide a specification for that, but the device should be able to handle driving a large load on the output for a brief duration. How long does your surge last? What is your common mode voltage when this surge occurs? Based off these details we may be able to suggest you a solution.

hello user463911,

As I have not heard any update from you, I presume you were able to resolve your issue. Therefore I am closing this thread. However, if you do need further support please reply below to reopen the thread and I will be happy to re-assist you.

The INA216 is connected to 5V power rail. As the power rail ramps up, surge current may last some mili-seconds. The sensing resistor + INA216 are sized to output ~1V for normal operation. Surge current can be > 5x than normal current. What happens to INA216 output during power ramp? - voltage and current?

You didn't suggest a solution. Why did you resolve my problem?

Sorry user463911,

There was a glitch on my end, it looked like there was no update. Looking into it right now.

Hello user463911,

I ran my own test on the INA216A1 as shown below.  Yellow is the input voltage to Vin+, blue is the voltage at Vin-, and pink is the voltage at the output all referred to ground.  I do see that the output is 5x greater than than what the expected output should be.  However, that peak decays in roughly 125us.  As such, I suspect you are below the recommended operating range (1.8V) for close to the duration of this surge you are talking about.  In this particular region, we do not have any data on the device functionality with respect to the drive strength and cannot make any guarantees in this operating region.  However, within the recommended operating region we have the data shown in the second figure below.  

As for startup output transient, you can reduce this output voltage peak by loading the output with a resistor.  With 500 ohms on the output I was able to get the output peak below 1V.

 

Thank you for taking the measurement.

I don't understand your assumption "you are below the recommended operating range (1.8V) for close to the duration of this surge". Your curve shows that INA216 outputs 5x than normal for some micro-seconds after 5V completes ramping (voltage is within INA216 spec.).

I used an 1k at INA216 output, and I don't know the load side impedance during power ramp. How did you estimate the voltage on the load?

Hello user463911,

Since you did not provide a shunt value or a load, I used 10mV for the Vsense as we have in our datasheet for Turn-on time and I used 5V for the bus as you mentioned in your post.  Based on tests I did, I noticed that longer power-on times corresponded to a longer duration of the undesired output. Despite this behavior relating to power on time, there is still a minimum duration of this behavior even if the device is powered on instantly.  This corresponds to the settling time of the device.  Below is my setup for the scope shot I posted above.  Below that are scope shots for slower power-on times. As before,  yellow is the input voltage to Vin+, blue is the voltage at Vin-, and pink is the voltage at the output all referred to ground.

Here is a scope shot of when I switch on my power supply, which has  a slow rise time:

Here is a scope shot of me manually dialing up the voltage on my power supply from 0V to 5V.

Patrick,

Thank you very much for doing the test again. It looks like when the voltage ramp rate is slow enough (~2ms per volt), the output from INA216 does not exceed the rail voltage at the output peak (~1V). Can you check how the output responds for 100 us ramp from 0V to 5V? 

Thanks for your help.

Hello user463911,

I ran my tests with the same setup as before, except with your desired ramp up rate.  Below is the result I get with the INA216 output open or basically seeing a large impedance.

Below is the result I get if I place a 500 ohm resistor between the INA216 output and ground.