DEMO MANUAL DC2343A LTC3335 Nanopower Buck-Boost DC/DC with Integrated Coulomb Counter Description Demonstration circuit DC2343A is a complete system level converter with an integrated precision coulomb counter solution for a nanopower buck-boost DC/DC with integrated which monitors accumulated battery discharge in long life coulomb counter. The DC2343A contains a PIC16F1459 battery powered applications. The buck-boost can operate embedded processor for communication to the PC over down to 1.8V on its input and provides eight pin selectable 2 USB and the LTC 3335 via its I C port. The GUI is capable of output voltages with up to 50mA of output current. The reading and writing all the control registers on the LTC3335 coulomb counter stores the accumulated battery discharge 2 as well as displaying and resetting all its alarm registers. in an internal register accessible via an I C interface. The firmware and software for the embedded system and The LTC3335 features a programmable discharge alarm the GUI are available at the LTC3335 solutions page. The threshold. When the threshold is reached, an interrupt is DC2343A uses two analog-to-digital converter channels generated at the IRQ pin. To accommodate a wide range to sample the battery and output voltages. The voltage of battery types and sizes, the peak input current can be samples improve the functionality of the GUI, and allow selected from as low as 5mA to as high as 250mA and optimal software correction to the measured coulombs. the full-scale coulomb counter has a range from 1.1mAh By adding the software correction the first order known (with 5mA I ) to 1793Ah (with 250mA I ). PEAK PEAK errors are compensated for over the operating range and Design files for this circuit board are available at the resultant coulomb count is accurate to within 3%. DEMO MANUAL DC2343A o p The demo board is pictured in Figure 2a and Figure 2b, The measurement of the V and the V voltages is BAT OUT with schematics shown in Figure 18 and Figure 19. The done with a sampled ADC reading to minimize power provided USB cable connects the demo board to the PC. dissipation and maintain the available accuracy from the With Linear Technologys QuikEval program running in processor ADC. Refer to page two of the schematic and the background of the PC, a five windowed GUI, pictured the V voltage measurement components for the fol- BAT in Figure 6 will pop up. lowing discussion. Resistor R18 and capacitor C11 form a 1.6kHz low-pass filter to remove the high frequency The GUI sends high level commands to the onboard switching noise from the V measurement. M1 is a BAT microcontroller via the USB interface. The GUI receives combination of a PFET and NFET configured with the the raw LTC3335 register values and converts them into PFET as a pass device and the NFET along with resistor application values, which are easily understood by the R24 performing the function of a level translator to turn user. The GUI also writes to the internal registers to set the on and off the PFET with the GN1 signal. This allows the accumulator value and the accumulator alarm threshold. use of relatively low valued resistors (R25 and R26) as The board is shipped with a peak buck-boost inductor the divider resistors into the ADC. The divider resistors current of 100mA and an output voltage setting of 3.3V. are needed to keep the input signal within the input range The board is configurable via jumpers to set the output of the ADC (0V to 4.096V). For the processor used on the voltage between 1.8V and 5V. Using a soldering iron to board the, input resistance to the ADC is recommended change the location of some 0 resistors and a different to be less than or equal to 10k. Both voltage sampling value inductor for the buck-boost converter, the board circuits (V and V ) are controlled by the same signal. BAT OUT can be modified to accommodate 5mA to 250mA peak At a 3 second sampling rate, the PFETs are turned on for inductor current settings. This flexibility is very helpful 120s to perform the ADC conversions. Performing both when working with higher-impedance batteries such as conversions within 120s every 3 seconds can add as much the Tadiran primary lithium-thionyl chloride (Li-SOCl2) as 35nA to the input current under worst-case conditions long life batteries. when the battery is at 1.8V and the output voltage is set to 5V. Under normal operation where the battery is 3.6V The demo board can be controlled by the GUI or by and the output voltage is 3.3V, the voltage sampling adds an external processor. When the jumper assembly on approximately 15nA to the input current. JP5 is in the B-C location the internal processor is con- nected to the LTC3335 device and the GUI is able to For a more details about the operation of the LTC3335 IC monitor the status of the registers. The B-C location is please, refer to the LTC3335 data sheet. the default for the DC2343A, as the PIC16 may consume current if left connected to the LTC3335 without the Connecting a DC9003A-B Dust Mote USB cable attached. When the jumper assembly on JP5 When connecting a DC9003A-B Dust mote to the DC2343A is moved to the A-B location, the onboard processor is demo board, two resistors in the Dust mote must be disconnected from the LTC3335. When in this location row changed for the mote to switch over from the battery power C pins can be used to control and monitor the LTC3335 to the output of the LTC3335, when PGOOD goes high. via an external processor. Change resistor R3 to 750k and change R4 to 5.1M, on the Dust mote demo board. In addition, connect J3 Pin 3 to E6 (GND). dc2343afb 2 rinciple perating