Guys can you help me?
I’m looking for alternative of MCP1754. Since I can’t find it in SOT89 package.
I have
L78L33ABU | Octopart and
MC78LC33HT1G | Octopart
But MCP1754 is 150 mA and L78L33ABU - 100 mA and MC78LC33HT1G 80mA
I’m not sure they are good enough.
Mouser UK appear to be willing to sell you one.
http://www.mouser.co.uk/Search/Refine.aspx?Keyword=mcp1754
If you’re using the a.c. adapter as the power supply, the choice of regulator is critical.
Hello Robert.
Thanks for response.
I’ve looked on mouser prices and 30 Eur for delivery item that cost 0.6 Eur is little bit too much.
Any comments on regulator that I’ve provided?
BTW any ideas why SOT89 package is used. I see hundreds of proposal in SOT-223 package on sites like Ali and Ebay.
If you are designing a clone of the emonTx, you must know what your requirements are. I don’t know whether you require a perfect clone, or whether you can relax some or all of the requirements. For example, if your input to the regulator does not have ripple content approaching 4 V (peak-peak, obviously) that the emonTx can have from the a.c. adapter, then both the power supply ripple rejection and the drop-out voltage assume less importance.
Regarding the current taken, it’s a simple matter of taking the currents drawn by the various loads - notably the processor, radio, temperature sensor(s), LED, any other I/O, etc and deciding which are under software control, therefore which are drawing current simultaneously; hence you determine the maximum current that your regulator needs to supply at any one time. And from that you can determine the current that it in turn draws from its supply.
I cannot comment on the choice of package, I believe @glyn.hudson did the board layout.
Origional EmonTx V3 power supply calculations are on the Wiki:
https://wiki.openenergymonitor.org/index.php/EmonTx_V3#Power_Supply