hi, had left electronics for more than 10 years. now doing some personal projects with the computer. looked up SATA's definition, where the 15Pin Power connector, pin 11 does provide an active low output that can be used for activity indication.

as i am a bit out of designing circuit, would like to ask some assistance. please refer to the attached for SATA's specfication of Pin 11's electrical characteristic. i am not exactly sure what that is telling me, IHAct, is that the Max 300uA that the harddrive can sink, or capabale of sinking?

i intend to use a PNP transistor, so whenever Pin11 is active (driven low), the LED will come on with just a base resistor, (do i need to pull it up to 5V?) a Collector resistor on the LED.

thanks for your help. cheers
h

 

Yes, it would appear that the maximum current you should draw is 300μA. That means for a 3.3V supply, the smallest base resistor to the PNP should be about 8.6K.

Note: You can't use 5V for your supply, the PNP emitter must be connected to no more than 3.3V. You don't need a pull-up resistor but you do need a resistor in series with the LED to limit its current.

 

thank you crutchow.

Would you recommend any quad SOIP PNP transistor that would be fully switched on at this little current? and it only states Max 300uA, so it could be less? would a FET be better suited?

thanks a bunch

 

You typically use a forced beta of 10 for a transistor switch so that would give a maximum collector current of 3mA. To get the 20mA for a typical LED you would need to add an NPN stage driven by the PNP.

A PMOSFET might be better, since you need only one transistor, but it would need to be a logic-level type that fully turns on at 3.3V such as this one.

 

please correct me if i am mistaken,


p11 (active low), pull up to 3V3, would this be good enough for that output to drive the PMOSFET?

 

please correct me if i am mistaken,


p11 (active low), pull up to 3V3, would this be good enough for that output to drive the PMOSFET?

That should work fine. You can use a 20kΩ or so for the pullup.

 

3V3 - 20k ohm --+
p11 --------------+---- gate

5V - source

drain - Rlimit - LED - GND

seem reasonable? thanks a lot.

 

3V3 - 20k ohm --+
p11 --------------+---- gate

5V - source

drain - Rlimit - LED - GND

seem reasonable? thanks a lot.

Your drain voltage has to be 3.3V not 5V. The SATA output can only tolerate 3.3V.

 

roger, will drive the LED with 3V3. thanks a lot.

 

roger, will drive the LED with 3V3. thanks a lot.

Hi all, it is quiet old post and I am looking for same thing. I've connected LED between pin 9 and 11 with resistor in series and my led stays ON all the time. Did you make it work and how did you connect everything in the end?

Thanks

 

I have found adapter on ebay and would use that to connect LED. I would like to make something like this https://www.ebay.ie/itm/331971997436
Do I need to break line from pin to make it work? Thanks