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ADUM6132.- Thermal problems (again)

Question asked by gilito on Jun 12, 2015
Latest reply on Jun 12, 2015 by bkennedy

I designed a power module (two full bridges) with mosfet (IRFR4510, forget PN in schema) and for gate drivers I decided to use Isolated PN ADUM6132.
Mosfet are in one PCB and drivers in other (stacked) via conector J4
I mounted several of them and my surprise was the high consume without to connect anything, I mean, no pcb with mosfet, input level to 0, etc,etc, so, doing nothing. 4 chips are consuming around 900mA in the 5V power supply and 13V in Vddb. But the most strange is the high temperature reached: in 3 minutes reach around 65ºC (and go on) (Tamb around 23º)
I follow all advices to do the pcb. (mainly planes in GND and GNDiso). PCB is 4 layer. Attached schema.

Specification says "The ADuM6132 is a power device that dissipates approximately 1 W of power when fully loaded and running at maximum speed" but if everything is stopped, where is the source of this consume? iF you disconnect Vddb, the consume fall down complety, biut you don't have isolated voltage (so, the undervoltage works fine).

 

Is this normal? To have 65ºC is not admissible in my design (mainly because I can achive 40ºC or more)
If this is "normal", and to resolve the problem (at least in several boards I've to deliver), is there any way to disconnect the dc-dc converter and connect externally 12V to Vdda? (I assume the high current and temperature reason is the dc-dc)

 

Thanks in advance

Saludos - Regards

Gil

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