need regulator circuit that is efficient at both low and high currents 1

[geekEE]

I'm designing a battery-operated device that needs a 5V supply that draws microamps when asleep, but about 2Amps when it's awake. If I use a switching regulator, it will be much more efficient when awake, but the current draw when asleep will be higher. If I use a linear regulator, it will be efficient when asleep, but dissipate a lot of heat when awake.

I was thinking about putting in both regulators and using auctioneering diodes to couple the outputs, but space is at a premium, so I was wondering if anyone knows a chip that already implements this scheme. Or if you know of some other way of tackling this problem that I hadn’t thought of, that would be much appreciated as well.
Thanks in advance,
Glenn

 

[VEBill]

Can you rewire the circuit to separate the microamp CPU (?) from the rest of the circuit that requires the 2A?

 

[IRstuff]

seems to exist, but you need to find your version:

http://cds.linear.com/docs/en/datasheet/1432f.pdf

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[itsmoked]

Most efficient is to use two separate regulators. Probably a linear for the low current and a switcher for the high current.

You need them both to have enables or you need to FET up switches in front of them that allows you to control them. Make the signals complementary so one is on while the other is off. Then you can just select which you want, probably with the circuit you're controlling.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[iop995]

For microAmp it's enough a resitor + zener, few series diodes or even same switching converter moved in pulse skiping mode; weak-up / move in normal mode when need more power.

 

[geekEE]

VE1BLL, unfortunately I'm using a CPU module that doesn't allow me to separate the low-current and high-current circuits.

IRstuff, that chip seems to change the behavior of the switching reg by putting it into a "burst" mode, but it still uses milliamps of quiescent current. I think there are switchers that have that mode built-in nowadays.

itsmoked, that sounds similar to my thinking, but without the power dissipation of a series diode. It adds a bit of complexity though (i.e. more chips in an already small space). I wonder if anyone makes a single chip that would work like auctioneering diodes, but without the voltage drop.

iop995, it seems like a resistor+zener would use more quiescent current than a good linear regulator. Series diodes might work, but I think they also wouldn't be any better than a linear reg.

Thanks everyone!
Glenn

 

[geekEE]

Update: I found that Linear Technology has PowerPath controllers that will work like dual ideal diodes.

Glenn

 

[itsmoked]

This is not exactly what I was suggesting above but it's certainly the same flavor and might give you an idea.
Design Idea Classic



Keith Cress
kcress -

http://www.flaminsystems.com

 

[iop995]

Check also this dual converter IC.

http://www.richtek.com/product_detail.jsp?s=319