S5GC FDICT-ND diode getting hot......

[shaku]

Hi All,
I have a question on S5GC FDICT-ND diode. I have used this diode into my DC-DC Power Supply circuit at Input side.
Here is the connection: -
DC + to Fuse to Filter circuit to anode of this diode and cathode of this diode to DC-DC switcher and output.
DC- to Filter circuit to DC-DC switcher and output/ground.

Now question is: - This diode generates too much heat while I was testing power supply circuit at 19.5V input and at 2.5Amp load. This diode can handle upto 5Amp per specification. My question is, why this diode is generating too much heat?? (I have flare temperature gun and it measures 278F on the diode (not acceptable) and rest circuit shows around 90-100F). What is the alternative of this diode?? What else I can do to reduce heat??

I would like to know reason why is it generating this much heat??

Thank you,
Shaku

 

[jiripolivka]

Is the diode really rated for 5ADC for a long time? Or pulsed?
Under 2.5 A a P/N junction in forward direction drops~ 0.7 V, so it develops almost 2W of heat. You should use a heat sink or find a larger-case diode that can dissipate ~2W without a heat sink.

 

[crutschow]

You could use a Schottky diode, which has a lower forward drop and thus dissipates less heat at a given current.

 

[shaku]

You could use a Schottky diode, which has a lower forward drop and thus dissipates less heat at a given current.

Thank you Sir!! May I know why it is generating this much heat? Is it common/normal for diode?

 

[FvM]

This diode can handle upto 5Amp per specification.

Unfortunately the datasheet doesn't tell how large the copper pours around both pads must be to actually handle 5A. Some datasheets of same package (SMC) components have respective information. You'll be probably surprized about the size.

There's no secret about diode power dissipation and overtemperature:
P = V*I
Δt = P * Rth,ja (thermal resistance junction to ambient)

Using low forward voltage diodes (schottky diodes) and implementing low thermal resistance is the only option. For reverse polarity protection, you should also think about effectively zero drop MOSFET switches.