Consultation about application of DDC114YU-7-F


#1

Hi!

I have a question of the application of DDC114YU-7-F. We plan to apply 12V to Vbe and 5V to Vce. It looks ok for the input voltage in the datasheet but there’s no information of the constraint of the input current. I suppose because the transistor has its own resistors and it could work out for the range of input voltage, -6V ~ +40V? Still, I wanna make sure our application can work out or not.

Thanks for your time and look forward to hearing from you soon.


#2

Hello @miao5169935,
It looks like input current is listed on page 3 of the datasheet.


-Robert


#3

Thanks for your information, @Robert_Fay!

The datasheet does show the maximum input current under 5V. However, in our application the input voltage is 12V.

Or can I understand it in such way that there’s no requirement for the minimum input driven current, instead, the input current shouldn’t exceed 0.88mA no matter what input voltage is applied?


#4

Hello @miao5169935, I have forwarded this question to my product manager to see if the manufacturer has any information on how the change in input voltage will affect current on this specific part.
Thank You
-Robert


#5

Thanks @Robert_Fay!

Look forward to hearing from you soon again.

Merry Christmas!


#6

The first page of the datasheet offers most of the necessary insights; if one considers the Vbe of the internal transistor “small” for guesstimation purposes (it’s probably around 0.6v) then applying 12v between pins 2 and 1 (or 5 and 4) is essentially applying it across a 10K resistor, and therefore input current will scale linearly with input voltage, to a first approximation.
image

Note that if whatever is making the 5v that you intend to apply across the collector-emitter junction is capable of supplying more than 70mA (or anything close, in practice) then you’re likely to destroy the device the first time you apply an input.


#7

@rick_1976 Thanks very much for your explicit interpretation.

In the datasheet it only outlines all the maximum operating voltage and current, and there’s no minimum operation requirements. If 12V is applied to pin 2 and 1, (12-0.6)/10 = 1.14mA is big enough to drive the transistor? However, it exceeds the maximum input current 0.88mA when 5V is applied to BE in the table below.


#8

@miao5169935 The part of the datasheet you reference is trying to tell you that if you apply 5v to the input, you can expect 0.88mA at most of current flow as a result.

Note that max & min values are two sides of the same coin depending on whether one is describing device behavior or application considerations; “It takes a maximum of X volts to turn the transistor on” is the flipside to “Apply a minimum of X volts to be assured that the transistor will turn on.” The former perspective focuses on the behavior of the part itself, and thus is the format typically used in datasheets; look just a bit further up that same page in the datasheet, and you’ll find the minimum value you’re after from an application perspective expressed as a maximum from a part behavior perspective.

Also, if you look further down that page, you’ll see that the part’s current gain is characterized as being at least a factor of 68; multiply that by your 1.14mA figure, and you get a result about 10% over the Abs. Max. collector current for the part–in other words, it’s probably enough base current for most any permissible amount of collector current one might care to switch.


#9

@rick_1976
Thank you so much for your thorough explanation!

Now I understand :grinning:


#10

@rick_1976 Although it has 1.14mA base current, if the collector is connected to 5V through a 10k resistor, and the load is a schmitt triger, the collector current won’t be bigger than 0.5mA, right?


#11

Correct, assuming I understand your description properly.


#12

@rick_1976 I just figured out that maybe the manufacturer made the transistor work as a switch at different voltage levels.

Anyways, thanks a lot!