choosing voltage regulator

Thread Starter

majorkuso

Joined Aug 21, 2009
59
I have a project to design that needs to be battery operated and last as long as possible, I am looking at using a low voltage mcu like a pic16lf1455 a lm35 and a pressure sensor and a speaker with small possibly push/pull or op amp for output. I figured I could try and run the mcu in extreme low power mode with timers to put the mcu to sleep and use the pressure sensor as an interrupt. with this in mind, how do I go about searching for and choosing a buck/boost converter that will drive the circuit while using something like 3 AA or 1 9v battery?
 

ericgibbs

Joined Jan 29, 2010
19,135
hi m,
What is the 'awake' operating voltage/current for each of the modules, PIC, LM35 and PP amp.?
Be aware of the LM35 lower operating voltage limit.
E
ESP1 01-Jun-18 14.10.gif
 
Last edited:

dendad

Joined Feb 20, 2016
4,503
If you are going to use a buck or boost converter, the long battery life will go out the window. The quiescent current of the power supply will eat up the battery.
Do not use a 9V battery. 3 x AA cells will be better, with a good low drop out linear regulator if you must, or just run it all straight on the battery and use the PIC's ADC internal voltage reference if it has one.
Power the LM35 from a port pin so you can turn it on just for measurements.
Why do you want an audio amp? Go with a class D on that can be powered down.
 

ebp

Joined Feb 8, 2018
2,332
There are a few buck controllers that will make a converter with very low standby current, but even they may be unsuitable. I've never used one, but I know someone who I think has. I'll be talking to him within a few hours of this post and will ask him about them. I think it is unlikely you would find a ready-to-use module. Switchers can be real pigs, but many of the modern single-chip converters can be very easy to use if you follow the recommendations in the datasheet. Lots of these parts have been introduced because of the requirements in things like cell phones.

Maxim and Analog Devices (including Linear Tech, which is part of AD now) are likely candidates, but there are likely a few others. I'd try a web search for micropower standby buck converter or the like.

It may actually be more efficient overall to use a micropower linear regulator to power the processor and use a buck converter with an enable input, controlled by the processor, to supply the power for the peripherals when required.
 

Picbuster

Joined Dec 2, 2013
1,049
Use a mcp170x series delivers 250mA Low 2.0 µA quiescent current ( less than the self unloading values from your cell's).
Picbuster
 

ebp

Joined Feb 8, 2018
2,332
Two recommended by a friend:
Linear Tech (Analog Devices) LTC1877 - nice, low quiescent, but expensive!
Texas Instruments TPS62745 - low quiescent, programmable (on the fly) output voltage, fairly cheap

Chances are the web pages for these devices will also show recommendations for similar or alternative parts.

One thing you will run into with these and similar parts is that they will be available in surface mount packages only, and some only in things like DFN and QFN, which are not the easiest of SM packages to deal with.
 
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