Do we need the eeprom/3.7v power supply

Bstamp_gps

I am little bit confuse regarding the ram / eeprom memory.

My actual propeller developments don’t need to store any data on eeprom.
Is it really necessary to have it?
If I download the application only on ram, what happens if I cut the power end restart?

Another question :
The rest of the circuit use 3.7v power supply. Is it acceptable for Propeller ?

Graham Stabler

The program is stored on the eeprom, without it the program is lost when the power is turned off.

3.7? Is this the nominal voltage from a battery like a LiPoly?

Graham

Bstamp_gps

Thanks for your reply, Graham. understood for the eeprom. I just have to add it on my pcb prototype [noparse]:([/noparse]

3.7 is a nominal power supply on pcb : LM2670 12 to 3.7v converter. Do i need another one for propeller?

sheers.

Graham Stabler

Over to parallax on that one.

Graham

Graham Stabler

The datasheet says 2.7 - 3.6v

www.parallax.com/dl/docs/prod/prop/PropellerDSv0.3.pdf

page 25.

Personally I'd add another regulator, it only needs to be a small one.

Graham

Paul Baker

I think you are misreading the spec sheet, there isn't a LM2670 which outputs a fixed 3.7V, there is an adjustable version that can be set to from 1.2V to 37V but this isn't what you described. Is this the statisitc you are refering to?

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Mike Green

You really need a nominally 3.3V supply for the Propeller and its associated parts (EEPROM mostly). The reason for the range is that power supplies are rarely "right on". Sometimes there are variations with temperature or with the input source voltage and the extra "headroom" allows for this variation. The 2.6V low end allows for a failing battery to run things just a little bit longer or allows you to use a backup supply with a blocking diode (with its voltage drop) and still have the supply within the "tested" range.