Cooling of SO8

The Microchip TC4422 is pin compatible and has somewhat lower output resistance. Some similar parts by IXYS are also pin compatible and have slightly better output resistance.

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I assume you understand that total gate drive power is fixed for a given switching frequency, gate charge, and input voltage, irrespective of total gate resistance. All you can really expect to do is offload some of the heat away from the gate driver IC and into the gate resistor. You could keep the TC4420 part and just increase the gate resistance value, but then you would have slower switching performance. Alternatively you could replace the TC4420 with a lower resistance part like the TC4422 and then increase the gate resistor value a corresponding amount. In this way switching performance will not be altered (for the better or worse), but some of the heat will be offloaded from the driver IC and more into the gate resistor.

Alternatively you could replace your MOSFET(s)/IGBT(s) with lower gate charge device(s), or decrease the switching frequency, or decrease the gate drive voltage...

Reply to
Fritz Schlunder
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The usual way with little SM devices is to track out the ground pins to an appreciable area of copper on the PCB, the leads and solder being much more thermally conductive than the plastic case.

Paul Burke

Reply to
Paul Burke

Hi, I'm using a TC4420-SMD as a gate driver ( 15V, 100kHz, Qg=0.8µC, Rg=5 Ohm). Now the board is finished and the creature gets pretty hot despite a little heatsink glued on top.Is there a pin-compatible IC available with perhaps a higher power dissipation and/or lower output impedance? Is there a better way to cool down the case ( no fan)? Rolf

Reply to
Heindorf

Paul Burke schrieb:

Hello, that's not a bad proposal and I'll consider this at any rate the next time. Currently there is little space available and the board is finished. BTW the frequency is 50 kHz ( two stages alternately switched on) and I calculate approx. 0.3W for each driver. With 25°C and the small heatsink it's tolerable, I think. But at 70 °C I've doubts. Rolf

Reply to
Heindorf

despite

time.

the

tolerable,

I don't know the device. But generally you should go for power packages for power devices. Ie. SO8 with an exposed thermal pad under it (which you solder directly to a copper fill with thermal vias to a plane). 0.3W is nothing - if you have problems even with a heatsink I guess you calculated wrongly ;-)

/A

Reply to
Anders F

Fritz Schlunder schrieb:

Hi, I think I understand the relation between drive power and gate charge / frequency.Usually we use the 4421/22. The choice fell upon the 4420 because of its availability in SO8.During all this part searching I forgot the pin-compatibility of both.I'll keep it in my memory in case of emergency.I didn't know that IXYS makes also such parts.I'll check it out. Ok, thank you, I think the 4422 will do it. Rolf

Reply to
Heindorf

10 out of 10.

RL

Reply to
legg

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