Is there a npn transistor in different pin order?

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Is there a npn transistor in different pin order?

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Contributor IV

hi,

I did not find a npn transistor place for help,so I just search some useful information here.

I want a npn tranastor which is different pin order, usually npn is pin1-base,pin2-enitter,pin3-collector,but I want a npn transistor's pin order is pin1-base,pin2-collector,pin3-emitter,of course in SOT23 footprint.

Thanks.

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Contributor IV

Tom,

  I admire you very much,for your so powerful and professional reply.

1:I careless drew a wrong shc picture,and after change soldering R,my sch. on PCB is following,C895 is for switch on-off quickly.

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2:I pay attention to your advice---"the transistor is on (drawing 1mA) with Vbe of 0.35V at 150C;it is better to put a pullup to 3V3 rather than 12V for R916;You should use a 60V or 80V transistor instead;pin defaults to a 100k pullup on reset."

I am going to use the second circuit npn+pnp to a good production in next design.

Are you from Amercan or China,Can I have your Msn or QQ number,for in future my question.

Thank you,big boss.

Henry

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Specialist I

> Are you from Amercan or China,Can I have your Msn or QQ number,

Neither. Australia. I don't work for Freescale. No.

Tom

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Specialist I

The first circuit now protects the CPU pin as the voltage is limited by the BE voltage.

The transistor might switch on and off (I'll work on that in a minute), but as the output CVBS_OUT_EN pin is connected directly to ground through two zero-ohm resistors, it isn't going to give much of a signal!

Are you within specs for the GPIO pin? The rated current into the GPIO is 1mA. Yours is 12V/10k or 1.2mA.

Q5 will turn on, but will it turn off?

The voltage on the base of Q5 is about 0.15V + 12*220/10220 = 0.41V. If this is in a car, the battery voltage tuns up to 15V or so, so it would be 0.15V + 15*220/10220 = 0.47V. Neither of those voltages will work at high temperatures. Looking at the Data Sheets for a typical transistor like the following shows the transistor is on (drawing 1mA) with Vbe of 0.35V at 150C:

http://www.nxp.com/products/automotive-products/discrete-and-logic/bipolar-transistors/npn-transisto...

http://cache.nxp.com/documents/data_sheet/BC846BM.pdf?pspll=1

So with that circuit the transistor will turn itself on at higher temperatures and voltages.

Why do you have R116 there anyway? The GPIO pin can turn the transistor on and off without it. As well, during reset, that pin will default to ON. Is that what you want? If it is, it is better to put a pullup to 3V3 rather than 12V.


The second circuit is a lot better. It doesn't have any protection against any faults, and it doesn't have any EMI/EMC circuitry. They will be needed for a "real product". As well, the SS9013 is only rated to 20V. That's easily exceeded in a vehicle. You should use a 60V or 80V transistor instead.

The SS9013 has a minimum gain of 64, so that 10k base resistor is fine.

have you considered the power-on reset condition? Read "36.4.314 Pad Control Register
(IOMUXC_SW_PAD_CTL_PAD_ENET_RX_DATA0)". That shows that pin defaults to a 100k pullup on reset, and that is enough to turn Q6 on at power-on. If you don't want that you'll have to add a pulldown resistor to that pin to make it work properly at power-on.

Tom

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Contributor IV

Tom,

Following is my sch. so dose it can work well? just use one npn but not two transostor.

When the imx6q turn off,the io is safe?

when the imx6q power up,is it ok?

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Please give me your recommend circuit for npn+pnp ,Thanks.

Following is ok?

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Specialist I

This is a forum for big 32-bit CPUs with millions of transistors. Not a good choice for your post.

You made a mistake laying out a board, or are you trying to replace a part that actually does exist with that pinout?

If one exists, tell us the part number. That makes it a LOT easier to find equivalents.

Otherwise you should have asked Google first. There are apparently "R" parts available, but they swap Base and Emitter and not Collector and Base:

http://www.eevblog.com/forum/beginners/do-they-exist-sot-23-pnp-transistors-with-non-standard-pinout...

But as the above says, if you messed up a prototype board, just install normal transistors upside-down, or in your case upside-down and rotated 120 degrees.

Tom

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Contributor IV

Tom,

Thank you so much,you are so professional.

I made a mistake on sch. design to swap emitter and collecctor.I do not have a available part number npn.

Maybe I am going to use normal npn on board,when I swap the soldering place of resisotr on emitter and collector.

The mistake of sch. following:the question is when GPIO1_27 OF IMX6Q is high=3.3V,Q5 is not stop,because the Vcollter is 12V which higher than Vbase.Can you have a good way to make this circuit work ?And the ixm6q'io-GPIO1_27 is not tri-stated when turn off its power-1.34-1.5-3.3,so the io is effect the Q5.The pinut of Q5 is normal npn.

Thank you.

Henry

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Specialist I

I can't understand how that circuit works. Or if it could work.

You have a PNP transistor shown, not an NPN.


With the PNP, the 12V will go directly through the transistor, emitter to base, through R239 and will likely destroy the CPU. The Data Sheet shows the MAXIMUM voltage allowed on any I/O pin is VDD+0.3V. Your circuit provides way more than that and at quite a high current (10mA or so). Some microcontrollers have a specification for "injection current" which means you're allowed to inject a few milliamps into the pins like this through a resistor.

The question about "injection current" has been asked before on this forum, and Freescale didn't answer the question:

https://community.nxp.com/message/612828

That means this CPU can't take any "injection current".

If the transistor was an NPN, the voltage divider created by R916 and R240 still put 6V back onto the CPU.

The mistake of the transistor orientation doesn't matter. The circuit has to be redesigned so it doesn't destroy the CPU. The circuit must never under any circumstances be able to put a voltage on any CPU pin that is outside its maximum range.

It doesn't matter that the GPIO pin is an output. It can drive up to 3.3v, but it can't keep a pin that is trying to go above 3.3V down to that when it is driving high. The pin is also an input when the CPU is being reset on its power-on. You have to design for that case as well.

You probably need to redesign it with at least two transistors. You want an NPN with the emitter grounded and the base driven from the GPIO through a resistor. The collector should then drive the base of a second PNP transistor through a resistor that has its emitter connected to the 12V rail.

That's a Car Battery? Do you know what the maximum voltage you can expect on that circuit to be? How about plus and minus 200 volts? They're the expected impulse voltages caused by power windows and windscreen wipers when the switches spark. You can expect 50V to 75V for a few hundred milliseconds - look up "load dump". Another thing car electronics has to withstand is someone stupidly jump-starting a car from a truck that has 24V batteries. Then people can accidentally install a new battery BACKWARDS. What will that do (-12V on the 12V rail is not good). Properly designed (and tested) car electronics has to withstand all of that without any damage.


Tom

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