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1/23/2018 11:39 PM
 

Hi at MPS,

 

are there any reference designs on how to use, lets say the MP2456 in an inverted supply (-12V) configuration? I have seen similar application at Ti, however since we already have the MPS products inhouse (2456 and others) we would rather stick to this one.

 

Regards Kenneth.

 
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1/24/2018 5:34 PM
 

Hi Kenneth,

 

Please refer to the circuits below constructing a buck regulator as a negative supply. Please pay attention to the grounding, current limit, and voltage rating. The voltage rating needs to be well above Vin-(Vout). 

 

This example uses MP1461 buck regulator.

3.3V input to -9V output without using enable signal. 

 

3.3V input to -9V output with enable signal. 

 

Thanks,

Kevin

 

 
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1/26/2018 1:02 AM
 

Hi Kevin thank you very much.

It seems like the MP1461 is quite new?

Do you know if it is possible to do this manouvre on MP2456 or other similar parts? Maybe there are no restrictions?

 
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1/29/2018 10:13 AM
 

Hi Kenneth,

 

Most of the buck regulators can be configured as negative supply in a similar way. I don't think there is a specific restriction, but extra cautious is needed in the design. The calculation in negative supply is different than buck regulator. For example, the Vsw rating is Vin-Vout in negative supply. If Vin = 5V and Vout = -9V, the Vsw rating needs to be higher than than 14V. 

Due to the reason every part is different, and most of the buck regulators are not designed to be used as inverted supply. Performance and features cannot be guaranteed as buck regulators. 

 

Thanks,

Kevin

 

 
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