Trying to understand a component - Page 1
Forum section: electronics / projects

author: viktor18
author_rank: Regular Contributor
timestamp: June 14, 2017, 08:15:49 pm
content: So, In troubleshooting a device, it has come to my attention that four PROFET Power switches is having some weird output voltage compared to a functional board. The input is equal (24v) but the working is outputting 9volts, while the non working device is outputting 0,75volts.I'm trying to use the component schematic to troubleshoot why it would give such a weird output, but there's so much technical terms. Here's the component:http://www.infineon.com/dgdl/Infineon-BTS410F2+E3062A-DS-v01_00-EN.pdf?fileId=5546d4625a888733015aa9b094463616

author: viktor18
author_rank: Regular Contributor
timestamp: June 15, 2017, 09:57:07 am
content: Does this mean that the device showing 9voltish on the output is a short-circuit detection?

author: bktemp
author_rank: Super Contributor
timestamp: June 15, 2017, 10:07:25 am
content: When the profet is turned on, the output voltage should ne close to the input voltage.9V and 0.75V are either a result of some leakage current with no load connected or something else is generating that voltage.Look at the IN pin. If it is low then this behaviour is normal, because the switch is turned off. When the IN pin is high, the switch is on and there should be a higher voltage at the output.

author: viktor18
author_rank: Regular Contributor
timestamp: June 15, 2017, 10:26:05 am
content: Input is around 3 volt on both devices

author: bktemp
author_rank: Super Contributor
timestamp: June 15, 2017, 10:59:38 am
content: At 3V the profet should be on, so the output voltage should be close to the input voltage.Something seems to be wrong, either your measurement or both boards. Is the 3V signal stable or could it be a PWM signal? That would explain the lower output voltage.pin 1, GND: 0Vpin 2, IN: <1.5V when off, >2.4V when onpin 3, input: 24Vpin 4, feedback: open drain low on failure, depending on the connected load this pin it may or may not provide a useful signalpin 5, output: close to input when on, otherwise lowerIf pin 3 is +24V and pin 2 is stable at >2.4V and pin 5 is not near +24V then either the profet is not working correctly or there is a short at the output.

author: viktor18
author_rank: Regular Contributor
timestamp: June 15, 2017, 11:55:59 am
content: I have rechecked the measurements for one board at least.Here are the following measurements:Pin 1 = 0Pin 2 = 0Pin 3 = 23.45Pin 4 = 3.94Pin 5 = 0.74So maybe it's working after all? I can't tell for sure if they are supposed to be on/off in the type of state that I'm testing them.. But if all three boards that had some problem to begin with (I switched out some TVS diodes and nothing blows now) maybe they are working?I just got genuinely confused because the "functional" board ( At least it was supposed to be functional ) outputted 9 volts in the same state. While my three other repair objects outputted only 0.75volts (but all of them outputted the same voltage on a total of 12 switches.)Perhaps I just got mislead to begin with and have sitting and trying to troubleshoot something that simply isn't a problem ( at least on the devices that I'm tried to troubleshoot)

author: bktemp
author_rank: Super Contributor
timestamp: June 15, 2017, 12:19:24 pm
content: What type of load is connected to the output of the switches?If it does not draw any current at low voltages, the output may float at a low voltage.For example if the load is a LED string consisting of 6 white LEDs in series with 3V each, it won't draw any current at all below maybe 15V. So even the slightest amount of leakage current in the profet will make the output float somewhere between 0 and 15V.If you add a resistor at the output (for example 10k to ground), the output voltage should be close to 0V when the profet is switched off.

author: viktor18
author_rank: Regular Contributor
timestamp: June 15, 2017, 01:07:28 pm
content: They are connected to a few output contacts, and during my troubleshooting I haven't been able to plug those units in. So perhaps it's in the off state due to nothing connected at the contact pins? I'm giving it a go and will try to plug the unit into a machine and see if it even starts. The only thing at those pins if nothing is plugged in is just some EMI filters and diodes.

author: viktor18
author_rank: Regular Contributor
timestamp: June 15, 2017, 01:17:13 pm
content: Basically figured out that they are there to provide electricity for some modules that is connected to this device. So it's probably at 0 because they aren't connected so nothing really draws current. Possibly.