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12Vdc to 3Vdc Regulator

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Dotnet

Member
Hello All - long time no post!!

I've got myself confused as to voltage regulators - I need my hand held for a minute.

I'm just revisiting a handheld battery powered lighting control project I was working on last year and just about to finalise the circuit.

For various reasons I have to use an existing (small) handheld enclosure which is designed around an A23 12V battery. Originally I was going to base the unit on a Holtek 12E which was going to be fine for 12V. I have since found TXE-433-KH2 module and the 'Splatch' antenna by Link Technologies. The TXE-433-KH2 is spec'ed at 2.7 to 5.2 V. So it follows a 3.3V supply would by ideal.

Now, since it is battery fed I don't particularly want to go down the 317 (linear regulator), Zener diode route because of battery drain so I have been looking at the LP2953 LDO regulator from National. (as, in addition, it would be nice to incorporate a low battery/tranmit LED flash function to the unit)

Maximum current will be 15mA (10mA for the LED, 5mA for encoder/transmitter)

So to my questions

1) Are there any better regulators out there which has low quiescent current drain for long battery life.

2) Would o implementing a 'start up' pulse to the regulator/battery circuit when a key was pressed be a better option. If so how would the start up affect the encoding and transmitting of the code(s). Will there be a problem with the length of time the key is pressed and the time it takes for the correct voltage to be 'delivered' and the encoding and transmitting of data.

Thanks in advance
Matt
 

Hero999

Banned
The LP2953 is a linear regulator and is no better than an LM317.

You need a switching regulator.

A Black regulator will probably do but use a 3.9V zener.

Official Home Page of Roman Black

It seems silly to use a small 12V battery, you should use a couple of AAAs or even a single AAA and a boost converter.
 

Dotnet

Member
"It seems silly to use a small 12V battery, you should use a couple of AAAs or even a single AAA and a boost converter."


Tell me about it!!!!!

Would a/the switching regulator you mention introduce any appreciable (sp) noise onto Vcc - what usual decoupling caps values do?
 

Hero999

Banned
Switching regulators are more noisy but they're much more efficient meaning the battery should last for over twice as long.

Decoupling capacitors should do the job, if they don't then consider adding a small choke (try 1:mu:H to 10:mu:H) or a ferrite beads to the output.
 

barf

New Member
Integrated Switching regulators are very easy to use and require minimal components. Look at National, TI, Semtech, and MPS to name a few.

Yes, they cost more than a discrete solution but they can be very efficient and provide excellent regulation, low ripple, and fast transient response. The websites have all kinds of appnotes and reference designs.

They do however produce more EMI, but if you follow the appnotes and keep the traces very short, you can keep EMI under control for even RF and sensitive analog circuits.
 

Dotnet

Member
Thanks for the replies.

I'm just trying out something else which warrants a new thread for a moment

Matt
 
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