Hello,
I still am kind of a noob in electronics, and I found out about schottky not that much time ago.
I'm creating a circuit with an MCP79410 RTCC, connected to an UNO (test phase, later it will be connected to a tiny); to retain data I enabled its backup battery (standard 3.2V CR battery), putting a "normal" silicon diode between the battery and the component.
Everything works fine, but why not squeeze more?
I heard that Schottky diodes can have a very low voltage drop (thus ensuring that the battery backup can last longer). Are there any drawbacks of using a schottky?
Thanks
Are there any drawbacks of using a schottky?
They are a bit leaky and noise. I would add an extra capacitor.
I heard that Schottky diodes can have a very low voltage drop
It depends on the diode and current it is lower but I would not say very low.
Ok, thanks…
The current is around 900 nA. I have a 100pF capacitor on the battery line…
Reverse leakage of a schottky diode might be several times the current drain of your RTC module.
Leo..
Reverse leakage rises exponentially with temperature, schottky's are bearable at room temperature, but
an issue at high temperatures.
Thanks guys for all of the replies.
Basically I'll operate at room temperature; I'm preoccupied by Wawa's post… Should I stick to the "normal" diode?
Should I provide more info in order to make a better decision?
Thanks a lot!
A common 1N4148 has a forward drop of ~0.5volt at that current.
You gain very little (.2volt) if replace it by a schotky diode.
Leo..
Maybe I'm missing something, but what is the purpose of the diode in this case? The MCP79410 has a separate input for battery and internal switching (if enabled) to go to battery if primary power fails. They don't show reverse voltage protection in the reference circuit.
MrMark:
Maybe I'm missing something, but what is the purpose of the diode in this case? The MCP79410 has a separate input for battery and internal switching (if enabled) to go to battery if primary power fails. They don't show reverse voltage protection in the reference circuit.
Ehr… when I bought it (almost one year ago), I found a sample circuit with a diode, very similar to this one (which incidentally has a schottky).
Assumption is the mother of all...
Low leakage diodes must be used with rechargeable backup batteries.
Measure the forward voltage of the diode.
It might already be a schottky (<0.4volt).
Leo..
Wawa:
Assumption is the mother of all...Low leakage diodes must be used with rechargeable backup batteries.
Measure the forward voltage of the diode.
It might already be a schottky (<0.4volt).
Leo..
No rechargeable batteries; It's not a schottky (1N4007).
Nevertheless I understood that the diode (if any is required) can be a normal one without a dramatic effect.
Thanks to all
You shouldn't be charging a non-rechargeable battery.
A 1N4001 is just as good for that purpose. See test results in Reply#49 of this post. The test code is posted in Reply#16 of the same thread.