LMR36520: Maximum value of current

Charlie Xiao

Part Number: LMR36520

Hi team,

In synchronous rectification, the peak currents flowing through the two MOSFETs are equal, which is the maximum value of the inductor current.

The current tolerance of the lower tube is smaller than that of the upper tube.

Does this mean that although the top tube current can reach 2.4A, it cannot exceed 1.8A in practice?

In practical applications, the current of the down tube can not exceed 1.8A or not exceed 2.3A or 2.8A？Thanks.

Best Regards

Charlie Xiao

over 3 years ago

+1 Youhao Xi over 3 years ago

TI__Guru* 78240 points

Hi Charlie,

Please refer to the datasheet description:

In short, both limits are active. For the low side, 2.3A is the typical value. Due to process tolerance and temperature effects, this limit can become smaller down to 1.8A or bigger up to 2.8A.

Hope this clarifies.

Thanks,

Youhao

0 Charlie Xiao over 3 years ago in reply to Youhao Xi

TI__Expert 7405 points

Hi Youhao,

Thanks for your answer.

Why is the current withstand value of the lower tube lower than that of the upper tube? Thanks.

Best Regards

Charlie Xiao

+1 Youhao Xi over 3 years ago in reply to Charlie Xiao

TI__Guru* 78240 points

Hi Charlie,

As mentioned in the datasheet, these are two layer current limits: the low side limit for regular cycle by cycle current limit during normal operation, while the high side one for short circuit protection in case the low side protection failed to protect. So the high side one has a higher limit threshold to not affect the normal current limit function.

Hope this clarifies.

Thanks,

Youhao

0 Charlie Xiao over 3 years ago in reply to Youhao Xi

TI__Expert 7405 points

Hi Youhao,

Thanks for your update.

In my opinion, the current protection of the down tube is overload protection. The current protection of the upper tube is to protect the MOSFET from being damaged. Is my explanation correct?

Also I would like to ask, in hiccup mode, the device stops switching for tHC. Does the stops switching here mean that both the top tube and the bottom tube are turned off? Thanks.

Best Regards

Charlie Xiao

+1 Youhao Xi over 3 years ago in reply to Charlie Xiao

TI__Guru* 78240 points

Hi Charlie,

Yes your explanation is correct. When stop switching in the hiccup mode, both high side and low side FETs are off.

Thanks,

Youhao

0 Charlie Xiao over 2 years ago in reply to Youhao Xi

TI__Expert 7405 points

Thanks you.

Best Regards

Charlie Xiao

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LMR36520: Maximum value of current