[sdiy] uPD444 RAM battery power

Adam Inglis 21pointy at tpg.com.au
Sat May 30 00:20:17 CEST 2015


On 29/05/2015, at 6:10 PM, rsdio at audiobanshee.com wrote:
>
> What are the specs on that protection diode? What's the part number?
>
> One thing I notice is that it seems you're increasing the reverse  
> voltage on that protection diode from 0.5 V to 2.0 V (that's  
> quadrupled). I did a quick search, and very few diodes have a  
> maximum reverse voltage of only 2 or 3 Volts, but it's possible that  
> you might be getting close to its limit. If there's any question,  
> another diode with higher reverse voltage capacity would be a good  
> idea.
>

Thanks all

The diode is quoted as DS442. Datasheets show reverse current 1 uA at  
4 volts. I'm measuring about 0.3 volts forward drop in circuit. So I  
should be ok.

The RAM datasheet quotes "Data Retention Supply Current - 0.01 uA  
typical, 10 uA max" - a rather large variation!

cheers
Adam



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