Hello,
I'm trying to find a solution that lets me regulate the output of a 5V supply to 500mA. The supply is attached to a circuit that could easily pull twice that current if I let it but I don't want to let it as that load is hard on my design and puts the design at or beyond the specified safe operating area (heavy demand on the battery especially).
I don't want to use a power switch that shuts off the output and especially not one that requires an EN pin to be reset. It would be tripping constantly and the output would be useless. What I need is an IC (or maybe new switching regulator all together) that I can set to provide 500mA like the way a battery charger chip does it (fixed current). The input to my power supply is a small 3.7V LiPo cell rated at 1350mAh and a 1A load really pulls the voltage/capacity down quickly. Does TI make a part or part combo that can do something like this?
Thank you.
The best solution is to use one channel of a current limited mux such as the TPS2113A. Select manual switching and set the digital inputs to always connect the power supply to the output. The TPS2113A has a adjustable current limit for the input/ouput.
Most of our power switches have current foldback or simply turn off the output during an over current event so they won't do for your application.
A current limiting diode (CLD) would be ideal but they are typically only good for a few milliamps.
Another method would be to use an andjustable output voltage LDO. You set the feedback resistors to program the output voltage to something higher than the input voltage. This makes the LDO always operate in drop out so the input is always connected to the output. There is no voltage regulation but the internal current limits circuits are still active. The down side to this is the accuracy of most LDO current limits are pretty sloppy so you may not always be limiting to 500mA.
Hi Scot,
Thanks for the advice. I looked up that TPS2113 part and it could be useful especially with the ability to set the current limit to whatever I want. The one thing the datasheet for this part does not tell me is how it reacts to currents higher than the programmed settings. I may need to pick up an EVM for it and give it a try.
The LDO idea is neat but I've never been a big fan of operating a device outside of its normal usage and expecting predictable results. :)
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