Battery Powered Equipment - Regulator Recommendations Wanted

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Hi, I'm looking for recommendations for two different scenarios, although they might both be met by one solution...

 

1) 9V PP3/MN1604, either primary cells or rechargeables, regulated down to 5V, or maybe 3V3, at up to 200mA.

 

2) 4 x 1.5V AA, either primary cells or rechargeables, regulated down/up to 5V, or maybe 3V3, at up to 200mA.

 

Efficient switching regulators only please.

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

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what's your minimum acceptable efficiency ?

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awneil wrote:

what's your minimum acceptable efficiency ?

 

I want to squeeze a reasonable amount of energy out of the cells. Happy with 80-85% operating efficiency. The trade off would be efficiency against dropout voltage. In case 2) I'd like it to work down to 4V as that seems to be where both alkaline and Nimh fall off the cliff. In case 1), using similar figures, it would need to work down to 6V to cater for 6-cell Nimh stacks.

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

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West Coast Jim should be able to recommend something, as he has had a lot of experience with this, you may be able to search for his threads as he has talked about that before.

Jim

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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My experiences have been going from 1V5 or 3V0 cell collections to 3.3V at a few ma average, 100mA peak. 

 

Thus, I don't think that I can contribute much. Most of the switchers I have used have a maximum input voltage of around 6V.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Hmmm, if I can find an enclosure with a battery compartment for 2XAA that might be an option. It's just that 4xAA and PP3 seem to be more common.

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

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Brian Fairchild wrote:
9V PP3/MN1604,  ... at up to 200mA.

Your customers won't thank you for the PP3/MN1604 option; they are outrageously expensive in retail.

They're OK for multi-meters taking 5mA or less but don't really like delivering much above 25mA or so. You'll be asking for 3.3/8 * 200mA = 82.5mA (8V = estimate)

 

I've done several PP3/MN1604 projects. The highest consuming one was about 6.5mA The lowest 2mA. In both I used a micro-power linear regulator

Even at those tiny currents, our customers complained about short battery life so we switched to 2xAA and used On-Semi low quiescent boost regulator.

This got us well over 1000 Hr and despite the increased BOM cost, everyone was happy.

 

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1) 9V PP3/MN1604, either primary cells or rechargeables, regulated down to 5V, or maybe 3V3, at up to 200mA.

 

2) 4 x 1.5V AA, either primary cells or rechargeables, regulated down/up to 5V, or maybe 3V3, at up to 200mA.

The UP TO could be very misleading....say the switcher draws 1ma, fine, big deal.  However, if you typically draw only 3 ma, then 1ma is a big deal long term.

So is there any need to be efficient at a light load (is there a light load)?

Many times this is the downfall of chipxxxx, which might initially look promising.

 

A 9V battery should generally be a very last resort, they have the absolute worst energy capacity (maybe other than a pea-sized coin cell).  A huge amount of the volume is wasted on the packaging of the individual cells.  Just have fun throwing them in the fire.

 

Likewise, 4 AA cells are highly likely better than 3, since for a given final load wattage, the current is reduced (double the Vin, Iin cuts in half).  

However fet & inductor losses are I squared R style, so cutting the doubling the current increase losses by 4X, or cutting to reduce by 4X.  You do get higher losses due to higher volt swings, but it is often a much lesser difference.

Going from 3 to 4 cells is 75% of the orig current, 075*0.75==> 56% of the original losses.

You notice this when dealing with 20 vs 40 amp circuits and a 1000 Watt driver....nice and warmer.

You can notice too at low currents and months vs weeks of operation.

Of course a poor switching wave can dump the best switcher into the pit.

This might give some idea of a clever way they used to do things surprise    https://www.orau.org/ptp/collection/Miscellaneous/pacemaker.htm

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sat. May 16, 2020 - 03:46 AM
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S-303015 Battery Cubes - New Age | Mouser

2S NiZn AA is 2.6V .. 3.8V; 2.8V is the minimum VCC for XMEGA AU if the USB device controller is active.

PSRR may be an issue (or not)

 


AAA and AA are consumer :

Conrad energy HR06 AA battery (rechargeable) NiZn 1500 mAh 1.6 V 4 pc(s) | Conrad.com

 

SubC are industrial :

Nickel-Zinc SubC Cells — ZincFive

 

edit : target

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Sat. May 16, 2020 - 01:44 AM
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N.Winterbottom wrote:

Your customers won't thank you for the PP3/MN1604 option; they are outrageously expensive in retail.

 

I have to admit that they are not my favourite battery.

 

avrcandies wrote:

Likewise, 4 AA cells are highly likely better than 3,..

 

OK, let's scrub requirement number 1.

 

So, I'm looking for a regulator to deal with 4 x AA batteries, in step-up/step-down or 2 x AA as a step-up.

 

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

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So, I'm looking for a regulator to deal with 4 x AA batteries, in step-up/step-down or 2 x AA as a step-up.

Ok, so is your typical load almost 200ma, or is that a peak and the typical only 10ma? ...that can make a big diff, since some chips include special mdes for light loads, or are offer poor efficiency at light loads but good at high loads.

Is the expected battery operating time a few hours, days, or years?...the longer timespan, the more the quiescent currents matter (little drips fill the wastebin).

 

for bucking (downward), say to 3.3v , take a look

http://www.ti.com/lit/ds/symlink/tps62745.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1589618720335

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sat. May 16, 2020 - 08:58 AM
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Whoah - Getting the right component here is essential for good battery life.  Things to consider:

 

Is there a physical power switch ?

When your instrument switches off does the micro cut the power to itself or go into deep sleep ?
Do you need an enable pin for the regulator.

Do you need a buck that can do 100% duty cycle. {Guess who got bitten here}

Do you need over-current / short-circuit protection.

Do you need soft-start.

Load step response - do you switch on any motors / high loads that could crash the micro if Vcc drops too much. {Guess who got bitten here}

 

There is so much choice in this category that this becomes a haystack full of needles problem.

 

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There's a Microchip part - MCP1702 - which will provide a quarter amp at 5v or 3.3v, and it's a low dropout part so it will work down to dead-battery level. It's not the world's best linear regulator, but it's pretty good and the significant part is the 2uA 'base' current. What that means is that the part effectively costs nothing to run; you only have the power loss dissipated in the volt or so you're not using.

 

I investigated a big pile of switched-mode and linear regulators recently (last couple of years) and found two issues with switch-mode converters if they were low standing current: many of them would switch modes as the power regime changed (we switched between tens of mA to a few uA) which was electrically noisy and upset the EMI regulations; once which did meet the EMI tended to be expensive (in production terms) or had peak Vin of 6v - and the manufacturers would not certify them, or even comment on the possibility, of working above the spec-sheet Vmax. The open circuit voltage of a set of alkaline AA's is 6.4-6.5v; 7.2v for lithium types, so that was a deal breaker for us.

 

Neil

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I have used MCP1702 and MCP1700.  Max input voltage for 1702 is 13.2V and for 1700 is 6.0V.  You can get free samples from Microchip.  I think they will give you 15 MCP1700 and 3 MCP1702.  I like them because they come in a TO-92 package and work with ceramic capacitors-in other words, inexpensive.