Need help with the Circuit

[elecLear78]

Please help me with the analysis of the following circuit. The main purpose of the IC BTS840S2 is to detect Open circuit, Short to ground and Short to 24V supply. The output is a load such as lamp driven by this IC and also detects error condition. The input to the IC is the switch status. There are two conditions with respect to the input it can be either ON or OFF and two conditions with respect to Load it can also be either ON or OFF. Now my main doubts are with respect to the IC.

1. Open load condition: I could understand that the voltage of 24v is divided between 68k and 10k when there is no load hence high resistance and hence the voltage appears at the pin 1 Analog input to micro. But whether this condition is true irrespective of whether switch input is ON or OFF.
2. when the output pin is shorted to ground. How to calculate the feedback current coming out of pin no 5. whether it is also same irrespective of input switch status? Similarly for short to battery?
3. I have real confusion with the feedback current IS how to calculate? The data sheet talks about the parameter kILIS. What is it? What value i have to consider?
4. The real confusion is with the truth table given in the data sheet. i do not understand anything about it.
Please help me or guide me to get the answers. i am not able to understand the data sheet. Thanks in advance.

 

[Tony Stewart]

Please help me with the analysis of the following circuit. The main purpose of the IC BTS840S2 is to detect Open circuit, Short to ground and Short to 24V supply. The output is a load such as lamp driven by this IC and also detects error condition. The input to the IC is the switch status. There are two conditions with respect to the input it can be either ON or OFF and two conditions with respect to Load it can also be either ON or OFF. Now my main doubts are with respect to the IC.

1. Open load condition: I could understand that the voltage of 24v is divided between 68k and 10k when there is no load hence high resistance and hence the voltage appears at the pin 1 Analog input to micro. But whether this condition is true irrespective of whether switch input is ON or OFF.
2. when the output pin is shorted to ground. How to calculate the feedback current coming out of pin no 5. whether it is also same irrespective of input switch status? Similarly for short to battery?
3. I have real confusion with the feedback current IS how to calculate? The data sheet talks about the parameter kILIS. What is it? What value i have to consider?
4. The real confusion is with the truth table given in the data sheet. i do not understand anything about it.
Please help me or guide me to get the answers. i am not able to understand the data sheet. Thanks in advance.
View attachment 93247

1. OC is detected internally by voltage drop on 20mΩ FET by expecting some current and shutsoff driver in specified time.
The output status does not change unless you have a weak pullup R on output.(24)
2. When shorted to gnd , output is disabled and Is= when shorted to Vbb , status is reported by Is will be less than expected.
3. Isense is Iout/5000 So k=5000 except not accurate <1A
4. Truth table shows either input state which applies to both 1&2 driver separately

 

[elecLear78]

Thank you for the reply. Can you please tell me how did you derive the 5000, from which page of the data sheet can i get this information. I am sorry but I did not understand your other points as well, may be i will once again read the data sheet and try to understand and ask you if I don't understand. I thought the OC is detected from the external resistor divider network. And also from my little understanding, based on the switch status the FET inside the IC, will either provide Low resistance or high impedance am i correct on this? If Shorted to ground happens will the IC not get damaged how is it protecting itself?

 

[Tony Stewart]

5000 is clearly indicated in table and graph vs I for k.

Not intended for loads <1A

If you dont understand datasheet, It is hard to explain better. Read footnote numbers.