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EN5337 High Impedance Output when disabled

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Hello,

in my design I am using an EN5337QI  to provide 3,3 V. I would like to have the possibility to switch to an external power supply to provide the 3,3V on request. 

My idea is to use the ENABLE pin to turn off the EN5337. However, are the VOUT pins high impedance when the ENABLE pin is low or would an external voltage harm the EN5337?

 

Best regards,

Nizlas

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Hello Nizas,

EN6337 will soft shutdown when the EN pin is triggered low, but once Vout reaches  0V the output will be high impedance.

 So the problem here that until EN6337_Vout reaches zero voltage there will be a high sink current coming from the external supply until EN6337 output becomes high impedance.

So if there is a bead or series resistor inside that loop, it will help to reduce the sink current to a safer level.

Unfortunately EN6337 doesn't have a pre-bias protection to avoid device damage during the startup when that external supply still on .

 

If you would like to use the external supply, so you must to maintain some delay >3ms between EN6337 and the external supply turn on/off transition to allow EN6337_output capacitor to discharge to <0.5V (the safer voltage level for the pre-bias condition).

 

Thanks,

Mostafa

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Hello Nizas,

EN6337 will soft shutdown when the EN pin is triggered low, but once Vout reaches  0V the output will be high impedance.

 So the problem here that until EN6337_Vout reaches zero voltage there will be a high sink current coming from the external supply until EN6337 output becomes high impedance.

So if there is a bead or series resistor inside that loop, it will help to reduce the sink current to a safer level.

Unfortunately EN6337 doesn't have a pre-bias protection to avoid device damage during the startup when that external supply still on .

 

If you would like to use the external supply, so you must to maintain some delay >3ms between EN6337 and the external supply turn on/off transition to allow EN6337_output capacitor to discharge to <0.5V (the safer voltage level for the pre-bias condition).

 

Thanks,

Mostafa

View solution in original post

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Beginner
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Hello Mostafa,

 

thanks a lot for your reply. Exactly the information, I was looking for. I assume that the EN5337 works similar to the EN 6337.

 

Best regards,

Nizlas

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