A New type of Switching Regulator - Simple Switcher Power Module LZM12002?

DavidM

Hi,

I have been working on several Switching regulator Designs over the years, all which require additional inductors, specific capacitors, fancy PCB Layouts, Heat dissipation requirements etc, and on average, depending on Amperage and Voltage requirements, can cost on average about $10 dollars for the circuit, for small quantities.

All of my designs ( using the Prop) run off batteries (12V SLA) So efficiencies are important. I also require High Currents 1-1.5amps for some of my designs.

One thing I have noticed lately is that some of the specialised capacitors ( TANTALUM, Low ESR etc) required by many switcher circuits have gone up in price and availability is uncertain, even though the regulator itself may be inexpensive.

So In my frustration with sourcing these hard to get capacitor and Inductors , I have just discovered the reasonably NEW type of switching regulator ( modules) , which so far seem to have many benefits..

The one I am interested is the National Semi - LZM12002.

This is an interactive link, flick through the pages for the videos. (I rather watch a video than read through specs!)

http://publications.futureelectronics.com/publication/fd32abfd#/fd32abfd/1

The advantages I can see is that the same PCB LAYOUT can be used for all your designs regardless of Vout or Amperage , The same regulator part can be used for say 5.0 Vout and 3.3 Vout as well, minimising the different parts in a BOM and depending on quantity, better pricing and availability.


You will need to shop around for reasonable prices..

http://www.findchips.com/avail?part=LMZ12002

So far "FutureElectronics" have the best price , around 5-6 dollars, (you have to inquire with them, to get better pricing than what is listed on the website)

Here is a link to where I am getting the price from..

http://www.futureelectronics.com/en/technologies/semiconductors/analog/regulators-reference/switching-regulators/Pages/5171517-LMZ12002TZ-ADJ-NOPB.aspx

Also, With the NEW PROP 2 which requires 1.8 V, and maybe more amperage than the current prop, that this device could be well suited for It, I am about to order one of the evaluation boards.

What do you think?
Are any of you familiar with these type of regulators?

Dave M

RDL2004

Have you ever looked at the LT3080 regulator? It is more expensive than say an LM317, but is low drop out, and requires very little in the way of support parts. No tantalum cap needed and only one resistor to set output voltage.



http://cds.linear.com/docs/Datasheet/3080fb.pdf

DavidM

Hi Rick,

Not a bad device, not a bad price, and it looks simple enough to use and keep the costs down.

I had a quick look at the specs, and although it says its "HIGH EFFICIENCY" , the data sheet does not mention the ACTUAL efficiency, being an LDO , I wonder what this could be?

The LZM12002 is about 90% +

Dave M

Phil Pilgrim (PhiPi)

The efficiency of an LDO regulator is entirely dependent on its idle current and ts input voltage. For example, if an LDO regulator's output is +5V and its input voltage is +10V, its efficiency can never be more than 50%. In this scenario, the "low-dropout" feature of the regulator is being wasted.

-Phil

DavidM

Hi Phil,

So with LDO's the efficiency of 12 Vin and 3.3Vout would be around say 25%! , Thats not good for battery power., But Say 12Vin with 5Vout would be about 45%? Is that Correct?

I have used various LDO's and whilst cheaper and easy to use, they all seem to suck up the juice if you know what I mean, So is there any point?

If I use a switcher ( LZM Series) for the 12 to 5 volts, and say the above mentioned LDO ( or similar) for 5 to 3.3 Volts, would the efficiency be about 65%?

In my next design Most of my 3.3 volt regulation is required for an RF Transceiver ( Aerocomm AC4490) it requires a MAX of 1.5 amps, at full duty, So an LDO would not be best for this, would it?

thanks

Dave M

Phil Pilgrim (PhiPi)

Closer to 59% if the switching reg is 90%: 0.9 * 3.3 / 5.

-Phil

RDL2004

Drop out voltage is just how low the input voltage can be before the regulator stops...regulating. A 3.3 volt reg with 500mV drop out will stop regulating when the input voltage drops to about 3.8 volts, at least, that's the way I understand it.

In your case a switch mode regulator is probably best, but for higher efficiency consider going to a lower voltage and/or different type of battery. You can get 6 volt SLA batteries (but wouldn't NiMH have more power per volume?) and the closer the input voltage is to the output the better the efficiency will be.

DavidM

I forgot to mention that I ALSO need to Boost the 12V to 48V, I have a circuit for this that works, but its currenly a through hole design, I need to make it SMD, So I need the AMPERAGE of the SLA to handle all of this.

12V SLA 2.2AH

Thanks

Dave M

max72

With a 12V supply I use the LM2594M series, not small footprint on the board, but it works well.
I also made a little batch of small boards that can be used in place of a linear regulator.
Massimo

bradharper

I'm currently using the LMZ12001 for 7.4==>3.3V and also need to come up with a solid 7.4==>5==>3.3 strategy.

I'd love to use two of them, but at lower quantities that's > $22 just to get on the board! The footprint and part count (5 resistors/4 caps) are nice though.

Attached is a reference layout for any DipTrace users.

RDL2004

NiMH batteries (AA size) typically come in 2.0 - 2.7 AH, so that should not be a problem. Two ways which SLA is better are low self-discharge and very simple charging systems. Maybe cost over time also to some degree.

Phil Pilgrim (PhiPi)

There are low self-discharge NiMHs available now, such as the Ansmann MaxE+.

-Phil

DavidM

Hi

Phil,

Those NiMh Batteries look good, If these can perform the same as SLA's then I may consider this in a future design, the idea of a lower input voltage sounds good as well, i.e more efficient!, but also a lot smaller and faster charging, I have seen some with a 1 year charge life!

Brad,

I am going for 2 X LMZ12002 , one for 12-5v, the other for 5 to 3.3Volt, I can get 100 pieces for about 5 bucks each, this will keep the design Simple and much less reliability on various parts, Can you tell me how they have performed for you< That PCB design you did looks very good!

Regards


Dave M