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Hi
We are using INA 193 current sensor for a battery charging application. We are using it for 24V as well as a 48 V application.
I have also attached the circuit used. It works well. After some 10 ~ 15 charge cycles, the current sensor failed.. ( Current sensor output is continouslly 0 volts).
The current measuring range is 0 - 5 A DC. We are using a 5 V power supply whose ground is isolated from the battery negative ( whose current is being sensed).
After the first failure, we replaced the sensor, again after some 10 ~ 15 charge cycles , once gain the sensor failed.
The current sense resistor is connected between charger +ve terminal and the battery +ve terminal. The output of the
INA 193 ic connected to an ADC of TMS320f28069..
Is it allowed to use this for a 24 V battery without any transient protection @ the sensor inputs ?
Is it allowed to use this for a 48 V battery without any transient protection @ the sensor inputs ?
What could be the other cause for the sensor output to go 0 volts... when it is sensing a current of around 3 A DC.. ?
Thanks
Lenin.
Hello Lenin,
I am sorry you are experiencing this issue. Thanks for attaching schematic information. I do not see anything overtly wrong about this circuit, but some more debug information would be very helpful. Whether you need transient protection depends on how fast and large the signals are. Could you measure the TP1 voltage when the charger cycles are starting/stopping?
Are the devices getting hot when they are breaking? Could you measure IB+ and IB- (voltages across R3 and R8) as well as IQ for a good part and bad part? I am also curious as to know if there is any voltage difference between INA193 ground and the battery/charger ground. Could you please measure this, if possible, with a multimeter?
Thank you for your understanding.
Best,
Peter Iliya
Current Sensing Applications
Hi Peter
Thanks for the response
Once you place a new INA193 in your system, please immediately measure the VR3 and VR8, as well as, the difference in between the two ground potentials to see if these values change over time.
- After placing the new sensor we found that the value is 1 mv. Also the voltage between the power supply Gnd and battery -ve have become zero.
1. Why are you isolating the two grounds?
- In the data sheet it has mentioned that the max voltage @ the differential inputs is 18 Volts. If the battery is not isolated from the ground, then the voltage @ the differential input will be equal to the battery voltage and hence will exceed the max limit of 18 V. Pls correct me if i got it wrong. In our case the sensor is @ the high side..
2. Why is your shunt resistor R7 0.01Ohms? At 1A, Vsense = 1*0.01 = 10mV
Thanks for this input , we will change the sense resistor.
3. Is the INA193 driving any type of load?
It's just used to sense the battery charging current.
Thanks
Lenin.
Hi Peter
I'm not sure about removing the isolation. Actually once we accidentally shorted this isolation. ( we were measuring the
battery voltage and the sensor o/p in the same scope ... the two channels were not isolated). After this the sensor failed
(sensor o/p becomes continuously zero V ).
Apart from this we use an AMC1301 sensor for sensing the battery voltage. The same power supply is being used
for both INA 193 and AMC 1301.. Shorting the power supply ground and the battery -ve will bypass the isolation of this AMC 1301..
Hence I'm not sure if i could bypass this isolation....
Also I felt that isolation would avoid the noise entering the micro controller, that's why we were using that AMC 1301 with isolation....
Kindly suggest..
Thanks
Lenin.
Hi Peter
Was this accidental connection of the grounds due to the oscilloscope probe being referenced to Earth ground? Were you able to gather valid, simultaneous measurements from INA193 and AMC1301 before the INA193 broke?
The AMC 1301 is being used for sensing the voltage of the battery which reads from a potential divider connected across the battery. Both these
sensors were connected to MCU ADC and based on these two signals the charge control was done, which happened perfectly for multiple charge cycles
until the INA 193 failure happened
What noise are you referring to? Is this common-mode noise at inputs of AMC1301? If the noise is common-mode noise at AMC1301 inputs, then this should be rejected by device, but if noise is differential across the shunt resistor, then this will not be blocked by isolation. The isolation is primarily meant to block voltages from input to output.
. We assume the noise is a common mode..
Could please provide a full schematic? The AM1301 can only have a common-mode voltage of VDD1+0.5V with respect to GND1. If your GND1 is connected to -ve and you are sensing high-side, then the common-mode is around 40V and this would break the device.
I'm sharing the schematic associated with both the sensors below. The common mode voltage here would be less than 3 V. Pls refer schematic. We had no issues with AMC1301 till now.
Regardless of the AMC1301 circuit, the INA193 should not have a isolated ground from the ground of battery.
In that case do you mean to say that both cannot be used together ?
Thanks
Lenin.
Hi Peter
Thanks for the response. We could try it out as per your suggestion. However would appreciate
if the data sheet of the INA 193 is updated, which specifies a maximum of 18 V @ the differential inputs.
Thanks
Lenin.