Battery powered design - linear or switching voltage regulators - Page 1
Forum section: electronics / beginners

author: MadBadCat
author_rank: Newbie
timestamp: July 15, 2018, 06:34:15 am
content: Hi everyone!Yay my very first post! : )TL;DR:What are the best practices to regulate multiple voltage levels (3.3 V, 1.8 V, 5 V altogether) in a battery powered device? Linear regulators vs. switching converters?I am a software engineer, trying to learn and produce stuff in electronics. The portable audio recorders that accept single or differential line input are among the relatively expensive music production gears e.g.https://www.amazon.ca/Zoom-H4n-Pro-Handy-Recorder/dp/B01DPOXS8I. I want to create a low-power, low-quality, cheap version, for myself.So far I have been browsing the various ADCs and codecs, mostly from TI. Several ICs I liked:TLV320ADC3101 Low power stereo ADCPower supplies: Analog: 2.6 V to 3.6 V | Digital: Core: 1.65 V to 1.95 Vhttp://www.ti.com/lit/ds/symlink/tlv320adc3101.pdfPCM3168A 24-Bit, 96-kHz/192-kHz, 6-In/8-Out Audio CodecPower Supplies: 5 V for Analog and 3.3 V for Digitalhttp://www.ti.com/lit/ds/symlink/pcm3168a-q1.pdfThese guys need multiple voltage levels to operate, not to mention the microprocessor is going to need perhaps yet another voltage level (5 V?)As I am aiming for a portable solution, I need to get all these levels from a single battery, most likely a li-ion of some sort. Being a noob, I am not quite certain how I should go about creating all these different levels.[What I can think of as a solution]Boost using a boost DC-DC converter to 5 V. Then use multiple buck converters to drop back to what you needBoost to 5 V -> Use linear regulator to lower to what you need, i.e. AMS1117Ditch lithium, use 2 AAA, use several boost ICs only -eliminates charging circuit too, but no more chargeable feature.Ditch lithium, use 4 AAA, use several linear AMS1117s -eliminates charging circuit too, but no more chargeable feature, heavier, less efficient, on a second thought why did I list this?Scour Digikey to find a single-voltage IC. (Not feeling lucky)Under these circumstances, what would a pro suggest to handle multiple voltage levels using a single lithium (or some other sort) battery(ies)? I understand there may be many factors going into this, however I am mostly curious about what the industry standards are for portable battery powered devices' voltage management (yeah, probably 10 hrs. worth of lectures to begin with but still).I will order most of the things I talked about and try on my own anyhow. That said, I'm welcome to hear any feedback/advice and could use a direction.Thanks!

author: Nitrousoxide
author_rank: Regular Contributor
timestamp: July 15, 2018, 06:55:39 am
content: Welcome to the forum!Depending on your noise requirement (PSRR of amplifiers), you may be even able to solely use a switching regulator. However, if you would like better rail performance you can place a linear regulator after the switching converter.Unless there is a specific need, avoid chaining switching regulators as it will decrease overall efficiency the more you chain (i.e. battery -> 5v boost -> 3.3v buck VS. battery -> 5v boost, battery -> 3.3v buck/boost).Your second point that you display is the closest to ideal, however, you must be aware that the power dissipated in a linear regulator is proportional to the voltage drop (and the current drawn). Thus it should be ideal that the switching regulator places the rail as close as possible to the desired voltage whilst also factoring in the drop out voltage of the linear regulator.Depending on what microcontroller you choose, you may not need to generate the core voltages. An example is the MSP432 series, it required an internal ~1.7v core voltage that is generated, and only to be used internally.If you really want to build to precision, you will have separate converters for analog and digital domains.There are plenty of PMIC's (power management IC's) that handle cell charging, protection and voltage conversion in a single package, its just finding the correct one based on the rails your require.Personally, If I wanted to balance performance with cost, I would boost to a common digital rail and then utilise a linear regulator to provide analog rails (from the boosted rail). Correct decoupling is also a must!

author: ocset
author_rank: Super Contributor
timestamp: July 15, 2018, 12:32:37 pm
content: it depends on the power requirement of each rail.Then you choose either switcher or linear reg.A single lithium can go down to 3.2v, so you may need a tiny boost converter to provide the bias power for which ever controller(s) you use (pwm controllers).Also, it can provide a decent gate drive voltage as logic level fets arent always applicable.