DC2343A: 3.3V @ 15mA, 1.8 ~ 5.5 Vin, Buck/Boost

Demonstration circuit DC2343A is a complete system level solution for a nanopower buck-boost DC/DC with integrated coulomb counter. The DC2343A contains a PIC16F1459 embedded processor for communication to the PC over USB and the LTC®3335 via its I2C port. The GUI is capable of reading and writing all the control registers on the LTC3335 as well as displaying and resetting all its alarm registers.

The firmware and software for the embedded system and the GUI are available at the LTC3335 solutions page. The DC2343A uses two analog-to-digital converter channels to sample the battery and output voltages. The voltage samples improve the functionality of the GUI, and allow optimal software correction to the measured coulombs. By adding the software correction the first order known errors are compensated for over the operating range and the resultant coulomb count is accurate to within 3%.

The DC2343A contains an LTC3335 which is a high efficiency, low quiescent current (680nA) buck-boost DC/DC converter with an integrated precision coulomb counter which monitors accumulated battery discharge in long life battery powered applications. The buck-boost can operate down to 1.8V on its input and provides eight pin selectable output voltages with up to 50mA of output current. The coulomb counter stores the accumulated battery discharge in an internal register accessible via an I2C interface.

The LTC3335 features a programmable discharge alarm threshold. When the threshold is reached, an interrupt is generated at the IRQ pin. To accommodate a wide range of battery types and sizes, the peak input current can be selected from as low as 5mA to as high as 250mA and the full-scale coulomb counter has a range from 1.1mAh (with 5mA IPEAK) to 1793Ah (with 250mA IPEAK).