current limit MCZ33996

luctronco · ‎07-06-2019

Hi,

The current limit of an output of MCZ33996 is between 0.9A and 2.5A (typ. 1.2A). Does this means that the current of the output is sometimes limited to 0.9A and sometimes it can be 2.5A. (very big difference).

what's the difference between MC33996EK and MCZ33996EK?

Best regards,

Luc

guoweisun · ‎07-07-2019

HI

Please note that below:

Using MOSFETs as output switches allows the connection of any combination of outputs together. The RDS(ON) of MOSFETs has an inherent positive temperature coefficient providing balanced current sharing between outputs without destructive operation. This mode of operation may be desirable in the event the application requires lower power dissipation or the added capability of switching higher currents. Performance of parallel operation results in a corresponding decrease in RDS(ON), while the Output Current Limit increases correspondingly.

Actually both MC33996EK and MCZ33996EK are same!

Thanks!

luctronco · ‎07-10-2019

Hi,

thank you for the information!

I have to switch 3 heater elements of each 800mA 24V (19W). After a few minutes via PWM I will reduce the current to about 400mA (50% duty cycle at 200Hz) and this will stay like that.

With an RDS ON of 0.55ohm we have about 0.352W power dissipation for each output. So in total 1.056W for a few minutes (0.352W x 3). (0.088W x 3 = 0.264W after a few minutes)

On the other outputs I will have a current of <= 200mA. 0.022W power dissipation maximum for each output -> so for the other 13 outputs maximum 0.286W when they are all ON with 200mA -> in reality only a few outputs of the 13 outputs will be used at the same time and most of the output currents will be <= 100mA.

Can I do this?

The maximum power dissipation of the IC is 1.7W without heat sink. So normally I think it should be okay.

The IC is mounted on a 2 layer PCB. At the top side the ground surface under the IC is about 200mm2 and via 12 via's the top ground surface is connected to the bottom layer with a ground surface of > 400mm2.

Top layer Bottom layer

Best regards,

Luc

guoweisun · ‎07-11-2019

Hi

I think you can do that,try it!

luctronco · ‎07-11-2019

Okay I will do!

Thanks!