DC-DC Step-up converter
February 11, 2010 6 Comments
MAX756_DC-DCconverter Final, with a AAA rechargeable battery
This is again a spin-off from another project, the IR Beacon for my robot.
For some reason I wanted the beacon to be independently supplied in electricity AND from a single rechargeable battery.
So I decided to use a DC-DC step-up converter, with the well known Maxim 756.
Right now it works, BUT there are some strange issues: it does generate the expected voltage (within 0.1 – 0.2 V if I were to believe my old voltmeter) but it can only hold it for currents of less than 100mA ! Whereas in the doc it says it should support 2-300mA !
If you have any idea about what might happen, don’t hesitate to leave a comment…
MAX756_DC-DCconverter
MAX756_DC-DCconverter2
Here’s for completeness, the circuit diagram from the specifications (it’s really quite simple, I didn’t have to do any other formal diagram, just wired the few components together):
MAX756 DC-DCconverter Diagram
Robotics / Electronics / Physical Computing 
Hi there,
in the datasheet is a diagramm called ‘Maximum Output Current vs. Input Voltage’.
As you can see, with 1,2V Input Voltage and 5V operating mode the circuit can just deliver an current near under 100mA. If you need 300mA Output Current, then the circuit needs an Input Voltage around 2,4V. Means you need 2xAAA accumulators in series connected, instead of just 1xAAA.
hope this helps.
Wow… don’t have the datasheet available right now to check, but it totally makes sense !
Thank you so much for finally clarifying this for me !!!
Dan
can you send me the circuit? I believe Sergey wanted have the circuit, too
meine-e-mail@gmx.de
sorry, I’ve never made a proper circuit diagram, I simply followed the quite simple one from the MAX756 documentation. I’ve just added that to the post for completness….
Прошу дать мне схему чтобы собрать инвертор на микро чипе MAX756. Пишите мне на zeos71@mail.ru Заранее спасибо
ooops, sorry I can’t read Russian…