Author Topic: Simple way to test fire this driver chip?  (Read 1004 times)

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Offline viper

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Simple way to test fire this driver chip?
« on: November 10, 2015, 06:05:23 am »
Doing a repair and suspecting the attached chip to be bad.  Due to the level of difficulty to even get to the chip by desoldering a double stack of boards, I really need to know if it is bad. 

The way it was connected in circuit are as such. 

Vcc - pins 1,6, are connected directly to the source 12V power provided through a pin connector.  There is no protection on those pins. 
GND - pin 2, there is a paralleled diode and 10K resistor to ground, same as examples in data sheets. 
CS-DIS - pin 5 has a 10k resistor to ground
Input - pin 3 hsa a 10K series resistor going back to an MCU output leg
Current sense - pin 4 has a 10k series resistor going back to another MCU pin. 

I am really not familiar with the chip or its internals and only need to determine if it works or not.  Probably easier  to test a known good one first but..... 

I need to know what voltages, resistors, etc I might use to give it a quick test.  I don't plan to run much if any real load off the chip but I guess a simple 12V load would be easy.  I really do not understand the input and current sense difference and use.  I figured this was more or less a FET in which the MCU is just operating the gate.  There seems to be more to this chip. 


Offline Psi

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Re: Simple way to test fire this driver chip?
« Reply #1 on: November 10, 2015, 08:09:40 am »
The VN5 chips are very hard to blow up.
They are protected from shorts/temp/reverse polarity etc.

12V on pins 1,6
CS-DIS 10k to GND
Current sense ~2k to GND
And a load connected between OUTPUT and GND (lamp or something, it needs to draw some current)

You should be able to switch the load on/off with a logic level signal onto the input pin.

If it overtemps/shorts/or the load goes opencircuit it will go into fault mode and the voltage across the current sense resistor res will jump up.

« Last Edit: November 10, 2015, 08:13:21 am by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)

Offline viper

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Re: Simple way to test fire this driver chip?
« Reply #2 on: November 10, 2015, 09:12:33 pm »
I think I have decided to just replace the chip as I really need a known good one to test against anyway and if I fry the old one on the bench, the test was be null anyway. 

But, to expand on my issues, somehow a desoldered diode has escaped!  I do have the markings but having trouble  ensuring the right replacement. 

Marking was "A4" with a sideways 7 at the end.  Looking up specs, it looks like this could be a schottky...  or not...?

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