| Electronics > Projects, Designs, and Technical Stuff |
| Nano current inrush switch/low voltage cutout |
| << < (3/5) > >> |
| Howardlong:
Thanks for the link. Typical temperature is room temperature, but I'll certainly keep that in mind. This is more of an academic exercise at the moment, although I do have some specific applications in mind for it if I can make if work as a system with the MCU. |
| SiliconWizard:
--- Quote from: Marco on March 13, 2019, 10:09:59 am ---The Torex parts seems hard to source, so the LTC1540 or ISL88001/ISL88014 seem most appropriate. No MOSFET needed, just use the output directly as the micro's power supply. --- End quote --- There's also the TPS3839x at just 150nA and fixed thresholds (no need for external resistors), if the 2.325V threshold is OK. The problem with both LTC1540 and TPS3839x if directly using their output is that their high-level output voltage (min) is 400mV below the supply voltage, which is a significant drop-out for such an application I guess. Given the very low power consumption of the system, the drop-out voltage is probably much lower but you're pretty much on your own (outside of the datasheet figures). The other issue is that there is only one threshold, whereas, if I get it well, the OP would like the system to be supplied if the voltage gets above 2V, but would like for it to keep operating down to 1.8V. |
| Marco:
The way the supply current for the LTC1540 rises during <2V operation is also a bit nasty. One more nanowatt comparator with voltage reference, TS9001. |
| Howardlong:
Yes, the low voltage behaviour is quite key, otherwise I won't have achieved anything other than added more complexity. I breadboarded up the EDN article on p102 here https://m.eet.com/media/1135665/31804di.pdf. It does indeed work: I set it up with a simple red LED load, and had to increase the trigger voltage by adding a further red LED in series with the green one. I used 1N4148 which aren't quite as good as 1N4007 in terms of reverse leakage current. It wouldn't work at 10nA but would at 20nA, although it would take about 150 hours to charge up the reservoir cap sufficiently to trigger! |
| David Hess:
--- Quote from: Howardlong on March 18, 2019, 11:01:08 am ---I used 1N4148 which aren't quite as good as 1N4007 in terms of reverse leakage current. It wouldn't work at 10nA but would at 20nA, although it would take about 150 hours to charge up the reservoir cap sufficiently to trigger! --- End quote --- Gold doped diodes like the switching 1N4148 and fast recovery rectifiers have much higher leakage currents. If you want a low leakage diode, then use a 2N3904 base-collector or base-emitter junction, or something like a BAS116 or BAS416. |
| Navigation |
| Message Index |
| Next page |
| Previous page |