Thermal Shutdown at 36degC Restart at 30degC TOP249YN Batch H636 E40613B
I have a couple of devices that I have installed the TOP249YN which work perfectly and have fan cooling on a heat sink which is securely attached to the heat sink with thermal paste. But on some TOP249YN devices, this switches off at 36degC according to my IR reader and turns back on at about 30degC. There is nothing wrong with the circuit. I have used the TOP249YN and set the X to reduce current using the resistor 20.49 Ohms. I could use a TOP246YN but I wanted the reduced transistor resistance advantage of the TOP249YN with is higher current capability. Unhappily I have a problem with some of the TOPSwitch-GX Family which is shutting down when it is still quite cool. The datasheet indicates the device should turn off at about 120degC with a 75degC hysteresis.
The mains supply here is 240Vac which is rectified to about 338Vdc. The Resistance from the supply is 680k X 3 = 2.04Mohm to the L terminal. The load is 50W
The other circuit has a PFC circuit addition where the supply voltage is lifted up to 390Vdc and the Resistance from the supply is 2M-ohm. The load here is 20W.
Its not all devices. The devices switching off while still low temp are numbered H636 TOP249YN E40613B
Please help. Thank you. Any suggestions.
Hi Anthem,
A couple of questions for me to try and help you.
You mentioned 36degC and 30degC, are you measuring the case temperature of the device? How long was it ON before it shuts down?
You also mentioned you can use TOP246YN. Have you tried it? Did you also observe the same issue?
Thank you!