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ADM2587E EMI and overcurrent problems

Question asked by stinf on Nov 7, 2011
Latest reply on Nov 10, 2011 by ColmR

Hello,

I am writing because I have some problems with the ADM2587E transceiver used in my system.

I have to premise I did not follow exactly the layout recommendations detailed in AN-0971, but only those indicated on the data sheet (my fault: I did not read through all the data sheet and so I did not find the chapter "EMI considerations" in it).

 

I have two kind of problems: EMI and overcurrent.

1) I have a 433 MHz RF transceiver on my board; it is evident that the presence of ADM2587E and its 360 MHz emission peak (measured at about -70 dBm with a spectrum analyzer) can often disturb the RF link, thus lowering range.

2) the whole system should be powered by a 3.6V primary lithium battery, which gives 70 mA at maximum; the RS485 link is at 115.2 kb/s and the power consumption is about 38-40 mA (whole board) when transferring data. As 40 mA < 70 mA, I would expect the whole system to work, but it does not: it appears to be somewhat "struck" at power on by a large current drain, which is certainly due to ADM2587E, as by powering it off the whole system powers on with no problem. From AN-0971 it seems to me this problem could also possibly be due to the layout "mismatch".

 

As the board has already gone through a little production, I would like to know if there's a way to mitigate this problem without changing my layout. For example, I could change capacitor values or technology, if necessary.

 

Can you please give some advice?

 

Thanks in advance,

Stefano Infante

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