DEMO MANUAL DC2043A LTC3305EFE Lead Acid Battery Balancer Description Demonstration circuit 2043A is a lead Acid Battery Balancer batteries. In CONTINUOUS mode, the balancing operation featuring the LTC 3305. The LTC3305 balances up to 4 continues even after the batteries are balanced to their lead acid batteries connected in series and incorporates all programmed termination voltage. voltage monitoring, gate drive and fault detection circuitry. The LTC3305EFE is available in a 7mm 7mm 38-lead The LTC3305 employs an auxiliary battery or an alternative TSSOP surface mount package with exposed pad. storage cell to transfer charge to or from each individual Design files for this circuit board are available at battery within the stack. There are two operating modes, DEMO MANUAL DC2043A p s Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN MAX UNITS V Battery Voltage Range 4.0 to 16.0 V BAT V Termination Voltage Range TERM2 = 0, TERM1 = 0 5 to 20 mV TERMINATE V Termination Voltage Range TERM2 = 0, TERM1 = 1 17.5 to 32.5 mV TERMINATE V Termination Voltage Range TERM2 = 1, TERM1 = 0 42.5 to 57.5 mV TERMINATE V Termination Voltage Range TERM2 = 1, TERM1 = 1 90 to 110 mV TERMINATE V Regulator Output Voltage Range I = 200A 2.4 to 2.6 V REG VREG G Le Refer to the block diagram within the LTC3305 data sheet the voltages across the auxiliary cell and BAT1 are com- for its operating principle. pared by the termination sense comparator. If the voltage difference between the auxiliary cell and BAT1 is less than The LTC3305 balances batteries using an auxiliary cell the selected termination voltage, the battery is deemed to or an alternate storage cell as a charge reservoir. The be in a balance state with respect to the auxiliary cell. The LTC3305 controls external N Channel MOSFET switches bottom switches will be turned off and the next battery in a preprogrammed sequence to connect a battery in the within the stack will be connected. stack to an auxiliary cell. Charge is transferred to or from the auxiliary cell when it is connected to a battery. If the voltage difference between the auxiliary cell and BAT1 is greater than the selected termination voltage, the The LTC3305 can operate in one of two modes, TIMER top switches that connect the positive terminal of BAT1 mode or CONTINUOUS mode, programmable via the to the auxiliary cells positive terminals through the PTC MODE pin. Balancing operation begins once the CBOOST thermistor are turned on. Current is limited by the PTC capacitor is charged to at least 6.95V. The EN1 and EN2 thermistor. Figure 3 shows the startup battery current pins select the number of batteries in the stack. where the PTC is limiting as it heats up. Figure 4 is the EN1 EN2 Application steady state battery current after the PTC has reached its 0 0 SHUTDOWN thermal equilibrium. After a 50ms delay, the termination 0 1 2 Battery Stack sense comparator starts to monitor the voltage across 1 0 3 Battery Stack the auxiliary cell and the battery. The battery will remain 1 1 4 Battery Stack connected to the auxiliary cell until the voltage difference decreases to the selected termination voltage or a t BAT timeout occurs. With the MODE pin set to 0 the LTC3305 will operate in the TIMER Mode. The BAL pin will be pulled low, indicating At this point all switches are turned off and the second that the part is enabled and balancing the battery stack. battery in the stack will be connected to the auxiliary cell The balancing operation begins with the terminal of the after a 50ms delay. This 50ms delay provides a break be- auxiliary cell connected to the negative terminal of BAT1, fore make function before the next battery is connect-ed. the lowest battery in the stack. The bottom switches that The cycle will be repeated for each battery in the stack. connect the negative terminals of BAT1 to the Auxiliary cells negative terminal are turned on. After a 50ms delay, dc2043af 2 princip operatin ummary erformance