This is Linear Technology Corp.'s second integrated synchronous buck/boost converter. The first, the LTC3440, rolled out about a year ago, providing some 600-mA output current. This latest LTC3441 is a 1.2-A version for products that need even more current.
Curiously, LTC is alone with this integrated design configuration that provides extended battery run-time. It performs the buck-and-boost mode from a single device and provides high (95 percent) efficiency to help you get more than you typically could out of a battery. No other parts out there have the four FETs on-chip doing the true buck/boost function. Some competitors offer buck/boost controllers that do something similar and there are other alternatives for either a buck converter with LDOs or a boost with LDOs, but they are not integrated on one IC.
Linear says that by integrating the functions on one chip it can extend run-times of battery-powered devices, especially MP3 players and digital still cameras. A synchronous buck/boost controller, by comparison, has a quiescent current of about 150 microamps, against Linear's maximum of 40 microamps.
The main application is for a 3.3-V system burst generated as a single-cell Li-ion battery goes down from 4.2 V to 2.7 V. This part allows the voltage to go below the typical 3.3 V and run the battery down as low as 2.7 V before it goes into the boost mode. Many designers are starting to look for this capability. For example, in MP3 devices manufacturers want to run the battery down as far as it can go before a recharge is initiated. Some of those designs are going down as far as 2.7 V. Running the battery down gives 10 to 15 percent more battery run-time when compared with stopping it at 3.3 V, and that's a big selling feature to the customer.
The LTC3441 also has burst-mode operation, which leads to good efficiency, even at light loads. Linear shuts down nonessential aspects of the chip in the light-load mode to get the quiescent current as low as possible-25 microamps.
The device comes in a low-profile 4 x 3-mm package and operates at a 1-MHz fixed frequency, so you need only a small, low-profile inductor. That means it's just right for footprint- and profile-constrained applications.