Can I use same LDO for two or three outputs? Given that the LDO provides enough needed current for three devices.
Electronic – use same LDO for two outputs
ldolinear-regulatorvoltage-regulator
Related Solutions
Looking at the application circuit, it seems that they have made on channel an LDO and another a Buck to save cost and component count.
- Core need higher current and lower voltage than I/O. Buck works better for that than an LDO.
- I/O needs somewhat higher voltage and less current (usually). LDO would be adequate.
Why not 2x bucks? Because a buck requires more components (inductor and better capacitor) than LDO. In this case, the combination of buck and LDO is a compromise of efficiency vs. cost and size.
It's not uncommon to use an LDO to power RF communication, analog front ends, because these can be susceptible to the EMI. At the same time, the digital section can be powered from a buck.
If you absolutely need 5 V, that is all your input is, and passive series filtering isn't enough, then a boost followed by a linear regulator does make sense. However, there is no point boosting to 12 V if you just want a clean 5 V. There are plenty of LDOs that can work with under 1 V headroom. Boosting to 6 V would provide plenty of voltage room to loose a little due to series filtering, then still provide enough for many LDO's to do their job.
A trick I have implemented a bunch of times now is to use the B-E junction of a transistor as the threshold detection above a LDO output. That's usually 600 mV or so. It's not hard to find LDOs that work with half that or less headroom. For example, here is a snippet of a schematic from a real product where I employed this trick:
The thing controlling the switcher pass element (Q1) compares the signal out of the R4/R6 voltage divider to a internal 600 mV reference to decide if the switcher output is above or below the regulation threshold. Q4 is set up so that it turns on when the "5.6V" line is the B-E drop above the LDO (IC2) output. The reason for scaling the collector of Q4 down with the divider is so that the system doesn't get fooled into thinking it is above the regulation threshold during startup when the voltage is rising and the LDO input might be 600 mV above its output even though the output is not yet in regulation. In that case Q4 still turns on, but the voltage divider prevents the feedback signal from reaching the 600 mV reference until the LDO input is close to full voltage. I've done this a bunch of times, and it has always worked very well.
Best Answer
If the regulator provides enough current, then yes, it is possible to power multiple devices (or loads) from it.
Let's assume you have a maximum of 10A available:
simulate this circuit – Schematic created using CircuitLab
As you can see, it will easily power 3 separate loads. If the total added up to more than 10A, then you have a problem. Otherwise, it'll be fine.
This is the same for any regulator. Any voltage supply, LDO, SMPS or whatever you want to use that provides a voltage can supply multiple loads as long as you don't go over the maximum.
Although saying that, it is always best to give yourself some headroom. If you have a 10A max, try not to go any higher than 9A for example, you will always get some unexpected resistances because the real world doesn't work in ideals.