| Electronics > Projects, Designs, and Technical Stuff |
| Micropower "kickstart" boost converter / joulthief |
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| Amper:
Allright, i found an acceptable way using a LTC3105 for startup, later pulling its shutdown pin with an ordinary n channel logic fet. It draws 12uA this way which is to much but the basic principle works and now i can look for different boost converters (like the ones posted before). This paired with the tn43U could result in a really sweet setup but ill still try getting it to work with just normal controllers. |
| Amper:
Andanother update: I just started playing with MCP1640 and while im pretty happy with them in terms of standby current (1uA as stated in the datasheet is easy to obtain without any voodoo) the efficiency at low input voltages is horrible. At this point i just enable it by a pull up and disable it by the attiny and then put everything to sleep until the brownout detector wakes it up again at 1.8V. right now it consumes 100uA@ 1.5V on average which is way to high and leaving the boost converter enabled consumes an extra 9mA without doing anything else. The 10uA figure stated in the datasheet is only realistic at high input voltages above 3V, i guess they dont supply the internal logic and transistor drivers from the output but use the input as its exclusive power source... |
| Marco:
How about TPS60310? There are of course proper 0.9V MCUs, just not tinys. |
| Amper:
I think i solved some issues, one or two software bugs, and a mistake i did in hardware. Also charging the storage more often (every few seconds actually) helped. I guess this way it operates in a better efficiency range. Now i just keep charging to 1.9V and went down to 14uA@1.2Vin and 20uA@0.9Vin. Efficiency wise this is also not amazing but im down to 20uW which is good enough for almost all applications. Though im toying with the thought of using an M41T62 RTC which i may need anyways as the watchdog. This will bring the current at high voltage down to 450nA and will result in roughly 2uA@1.2V. Thats insanely low power. The reason i dont really want a low voltage controller is that i plan on controlling other hardware and even writing to SD will need 3.3V an when i have to have a boost conveter anyways i may as well keep open all the range of atmel cpus. |
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