TPS54335A: Operation of EN pin

Hi

  It is recommended to use an open drain logic to drive the EN pin instead of driving it directly.

It should be pulled up to an internal LDO voltage.

Regards,

Gerold

Hi Gerold

Thank you for your reply.

What is the output voltage of the internal LDO?

(Our customer asks about the voltage value being pulled up)

Regards,

Y.Ottey

Hi, Ottey

Internal LDO output is 5.5V. 

The pulled up voltage value will be lower than 5.5V. 

Zhao

Thank you for your reply.

Is it because the internal pull-up is the reason for controlling the EN terminal with open drain?
For example, if it is directly controlled by the IO of the MCU like this time, it is pulled up internally, so I think that the EN pin will not become Low even if a Low signal is sent by the IO of the MUC.

Regards,

Y.Ottey

Hi, Ottey 

No, EN pin can be interfaced with not only open drain, but also can interface with MCU's IO. 

The EN's internal pull up current is very small, it is only ~4uA, the MCU can pull low it. 

Hi Zhao

Thank you for your quick reply

I understand that the IO of the MCU (CPU) can also control the EN pin of the TPS54335.
Why is the EN terminal control recommended for open drain or open collector in the data sheet?

Regards,

Y.Ottey