I have a project I would like to run on a 3x AA battery pack, but need to regulate the voltage for the I2C sensors being used. As its a long term data logging application, constant & quiescent currents are an issue. I have been looking at the S7V8F3 as an option to regulate just the I2C bus & I2C sensor supply, but I don't want to put that voltage regulator into full shutdown, because the sensors take so much time to re-stabilize on power up, and the eprom registers all reset away from optimal. The sensors can respond much more quickly if I just let them "sleep" at a few ?A each while the main datalogger itself sleeps (usually for 15 minutes at a time)
So my question is: how much current overhead does the S7V8F3 draw when it is only supplying about 10 ?A to the "sleeping" sensors? (the site only lists quiescent current for "shutdown mode" with no load, which is not what I am doing)
I may be wrong here, and someone may know this product well. But I suspect you aren't going to get a sensible answer to your question about the quiescent operating current. Even if I could decipher the regulator part number, which isn't clear from the printing visible in the photographs, without knowing the value of all the other components it would be impossible to know the operating point and derive the supply current.
The only way I think you'll know is to buy one (or a few) and test it (them), and even then there's no guarantee that the quiescent current won't change with the next batch since it's not a published parameter.
Personally, I would look for alternatives to the sensor you're using to see if there's a ratiometric alternative (which provides an output proportional to supply voltage), or something with a faster start-up time. I see you're designing a flow meter, but what's the sensor?
Okay, so I'll contradict myself: I've identified the chip as a Texas Instruments TPS63060DSC. The data sheet gives the typical quiescent as 30uA (60uA max) with 5V input and 0mA output, which is consistent with the Pololu claim of <0.1mA. So in your position, I'd work with a value of 100uA input current when driving 10uA output, but get one and test it to be sure. Don't even think of using the shutdown feature, since the input pin has a 100k pullup and pulling it low will take 45uA with 4.5V battery voltage. Hope that helps.
Post your question the Pololu Products forum. You will find the engineers to be very responsive and competent.
Thanks to you both. 100 uA would still be better than many other regulators quiescent current, but I will just order one and see what the actual truth is.
And I should have thought about the Pololu forum myself, but I immediately thought of the Arduino playground as there are so many folks out there who have tried one thing or another, and have experience with parts in "real world" combinations. I will try to post this question to them there now, and if/when I learn something useful, I will pass it back to this thread.
Just been skimming over your blog: fascinating project! I guess the sensor you're needing to keep alive is the 3-axis magnetometer. Can't see any realistic alternative to what you're doing. I'm going to post a tutorial on thermistor temperature sensing for anyone else interested in simple temperature measurement using a spare ADC input.
For anyone interested in more advanced temperature sensing, including how to avoid thermistor self-heating and use of the more accurate Steinhart-Hart equation, send me a PM and I’ll consider a sequel.