Anablog

I just got a press release from Analog Devices about their new ADP2503 and ADP2504 0.6/1 ampere buck-boost switching regulator chips. They are $1.40 in 1,000-unit quantities. I thought this would serve to launch a shameless plug for my article about buck-boost converter architectures. What is cool about this chip is the high operating speed. Doing a buck-boost converter is a real control challenge, you have to segue between the buck mode and boost mode and back again. If you are hooked to a nice low impedance battery the lower noise from that source may make things a bit easier, but remember, when you drag a slug of current out, it lowers the voltage so maybe the converter IC then thinks it should go into boost mode, but really is should stay in buck. And do remember to test the system with failing batteries that are going high impedance and can’t deliver a charge. Experienced engineers are familiar with both kinds of batteries, those that have failed and those that are about to fail. This is a case where the IC companies have really added value by doing a very complex control loop inside a chip.

This chip is for the common situation where you have a single lithium ion cell that needs to hold up a 3.3-volt rail. There are other buck-boost applications such as LED lighting and wide-range wall-warts. And my pals at National Semi, TI, Linear Tech and Supertex, to just name a few, would feel slighted if I didn’t mention their parts. Be aware that the control algorithms are different for different companies so it is worthwhile to check out how different company’s parts work in that critical transition phase. The ADI part has integral FETs, if you want mojo current, Linear Tech makes a high-voltage controller that you can use with discrete FETs (pdf).