• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Best Voltage Regulation

Status
Not open for further replies.
I'm using a primary battery with 3.67 nominal voltage. The circuits I'm using are able to take a max of 3.6V. It's a small difference, my plan was to use a 500nA quiescent current LDO, but are there other options? We want a long battery life, so I don't think a shottky diode would help. The circuit consumes <6uA in sleep and <3mA while active with a duty cycle of <1%.

Thanks for any thoughts!
 

Tony Stewart

Well-Known Member
Most Helpful Member
adding 0.5uA to 6uA sleep mode with LDO is good and negligible considering average current is 1% of 3mA=30uA and thus 0.5uA/30uA is <1.5% increase.

does this become Vref for ADC? then the question is , what Vout do you choose to keep constant at end of charge life? and does this need UVP to disable draining battery further or send message for low voltage.
 

ronsimpson

Well-Known Member
Most Helpful Member
MIC5232
You can choose 3.3V or 2.6V
1.8uA is wasted.
You need about 0.1V head room.
 

AnalogKid

Well-Known Member
Most Helpful Member
1. You would need a voltage regulator with less than 70 mV of minimum headroom. Possible, but very difficult.

2. 70 mV is less than 2% of 3.6 V. As such, it is less than the standard voltage tolerance for the vast majority of voltage regulator devices, and well within the operating voltage range of most low voltage ICs. Whatever is running on the 3.6 V will be fine without any need for a regulator circuit.

Of course, this would be much easier to answer if you would share information about the circuits you are using. Have you read the datasheets regarding the operating voltage ranges? It is important to note that the operating voltage *never* is a single, absolute number. It always is a range of values, with +/-5% a very common range.

ak
 

ronsimpson

Well-Known Member
Most Helpful Member
AnalogKid,

I think he does not want to drop from 3.67 to 3.6. So this 70mV is wrong.
He has parts that have a max supply of 3.6. But I think they should be run at 3.3V or 3.0 or 2.8V etc.
Next problem is the battery. During charging the voltage might get close to 4.0V.

I think he needs to keep the voltage below 3.6. So a 3.3V LDO regulator will work. It will keep the high voltages off his parts and when the battery voltage drops too low it will pass the power through with out regulating.
 
No ADC in this design -
AnalogKid,

I think he does not want to drop from 3.67 to 3.6. So this 70mV is wrong.
He has parts that have a max supply of 3.6. But I think they should be run at 3.3V or 3.0 or 2.8V etc.
Next problem is the battery. During charging the voltage might get close to 4.0V.

I think he needs to keep the voltage below 3.6. So a 3.3V LDO regulator will work. It will keep the high voltages off his parts and when the battery voltage drops too low it will pass the power through with out regulating.
I was thinking 3.3V - one part is annoying and it's voltage range is 3.0 - 3.6V, so it'd be risky using 3.0V I think.

But these are primary cells actually, so no charging - using Lithium Thionyl Chloride batteries.
 

ronsimpson

Well-Known Member
Most Helpful Member
MIC5232-3.3 will give you 3.3 out when the battery is more than 3.3 by 60mV. (at 3mA)

If the battery gets to 3.1V the output will be 3.04V if the current is about 3mA.

If you are sure the voltage will not get above 3.67 you are probably OK with out a regulator.
 
If you are sure the voltage will not get above 3.67 you are probably OK with out a regulator.
I was wondering about that - I guess that's a case where these devices might not be guaranteed to work, but they probably would... I don't know if there's a way to quantify the odds of the devices working.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top