PROC reverse polarity test?

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AnWa_1259496
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I was wondering if anyone, including Cypress, has determined the result of a reverse-polarity supply on a PROC BLE chip or module?

   

A product using a CR2032 battery will usually have a possibility of the user inserting the battery backwards. Designing a polarity protection circuit with a very low voltage drop presents a challenge.

   

I do know from testing that "another well-known manufacturers" bluetooth chip will have a damaged radio if this happens although the CPU will still work.

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Bob_Marlowe
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Usually the mechanics of a CR2032 prevents applying a reversed voltage when the battery is inserted upside-down. Cheap or too simple coin-cell holders may not have this option.

   

 

   

Bob

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AnWa_1259496
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The type where the battery slides in sideways dont usually have any protection, but I will look at whats available.

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ETRO_SSN583
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If you do not have a mechanically constrained approach there are

   

some pretty low drop Schotkys available that will lose very little

   

headroom in a battery backup design, sub 200 mV for mA kinds

   

of current.

   

 

   

    

   

          

   

http://electronics.stackexchange.com/questions/96059/switch-between-battery-and-usb-power-no-microco...

   

http://www.maximintegrated.com/en/app-notes/index.mvp/id/1136

   

   

 

   

Regards, Dana.

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Bob_Marlowe
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One contact is made at the rim of the cell, the other in the midst. When the cell is inserted upside down, there is still the contact at the rim, but the midst contact is now on the same side as the rim is. So there is no polarity reversal.

   

 

   

Bob

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AnWa_1259496
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 Bob, I believe the type you are referring to is the one commonly used on PC motherboards where the battery slots in from the top.

   

I have yet to find a "letter box" type with polarity protection, suitable for a keyfob etc. Not really sure why, as it cant be difficult to design a type with side contacts for positive and a pad on one side for negative, which the battery slides into.

   

The other question is, if using a reverse-polarity protection circuit with a forward voltage drop, does that increase the overall power dissipation or is the power wasted by the protection offset by the fact the chip is running at a lower VCC?

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Bob_Marlowe
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Like this one?

   

 

   

Bob

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AnWa_1259496
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 Needs to be horizontal not vertical.

   

Mr Picky here 🙂

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Bob_Marlowe
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Bend the wires?

   

 

   

Bob

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AnWa_1259496
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Bending the wires might work, we will need to get samples and evaluate this in a manufacturing scenario. 

   

Incidentally the method I went with in the aforementioned design using the "other" BLE product which was for  German car company was to use an Si2323 MOSFET in series with gate to GND. This gives a very low voltage drop.

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