Charging chips similar to the LTC4054?

Products & Technology DSO Nano
#1

I am curious as to what other charger chips can be used instead of the LTC4054. I happen to have a MCP73832 by Microchip, does anybody know if this will work? (microchip.com/wwwproducts/De … e=en026250). If not, is there another charger by Microchip that would work?

Thanks

#2

Hi eng444,

See my recent post in another part of this forum: viewtopic.php?f=12&t=676&start=10
about half way down the page.

Shazam

#3

Thanks a lot! I will keep an eye on that post for sure. Is it necessary to use the Fairchild IC? Or is it just there to help use the DSO while charging?

Also is there a big difference between the MCP73832 and the MCP73831? ie can I use the MCP73832 instead of an MCP73831? Ideally I would like to just solder in the Microchip IC and whatever else is needed with the given space on the circuit board.

Thanks :smiley:

#4

Hi eng444,

The two charge regulator ICs are the same except for the status pin #1. The ’31 has a tri-state output which can indicate “charging” and “finished charging”, the’32 has an open drain, which is low when “charging”.

If you understand detailed FET specs, any P-channel with the right specs (like the one inside the Fairchild IC) will work. The same applies to the Schottky Diode. The Fairchild combination is optimized for this application, small, and inexpensive.

Perhaps you are not getting the full picture, though. The PCB must be changed or modified by cutting traces and adding jumpers. Just adding the missing IC is a waste of money, because it is bypassed by the Diode. If you remove the diode, then the scope won’t run because of the low voltage due to current limiting while charging the battery. That is why the diode was added, but since this bypasses the charging IC, there is no point in installing it.

Shazam

#5

Hi Shazam,

Thanks for replying. I understood that the addition of the Fairchild IC would require modification to the board, which is something I may undertake someday, but for right now I have the Microchip charging chip and would like to make as simple a modification to the unit as possible by using the existing traces. As far as I understand it right now that would involve removing the diode and adding a few other components (resistors and capacitors as called for in the revision documents I’ve seen elsewhere on this forum for the charging circuit that was designed but not used). I also understand that I will not be able to use the DSO while charging, but for right now that is acceptable to me.

Thanks, I hope that makes sense :slight_smile:

#6

Hi Shazam & Eng444,

my DSO has the diode removed (by myself) since i bought it and the LTC4054 mounted. I’ve used it for 6 months and have no issues so far. The thing is that DSO & battery share the available current and the LTC4054 outputs a variable voltage. Obviously not the right solution to charge the battery but it’s far better that a diode alone.