DEMO MANUAL DC2043B LTC3305EFE Lead Acid Battery Balancer DESCRIPTION Demonstration circuit 2043B is a lead-acid battery balancer batteries. In CONTINUOUS mode, the balancing operation featuring the LTC 3305. The LTC3305 balances up to four 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 means 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 DC2043B PERFORMANCE SUMMARY 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 OPERATING PRINCIPLE Refer to the block diagram within the LTC3305 data sheet voltage difference between the auxiliary battery and BAT1 for its operating principle. is less than the selected termination voltage, the battery is deemed to be in a balance state with respect to the The LTC3305 balances batteries using an auxiliary battery auxiliary battery. The bottom switches will be turned off or an alternate storage means as a charge reservoir. The and the next battery within the stack will be connected. LTC3305 controls external N Channel MOSFET switches in a preprogrammed sequence to connect a battery in If the voltage difference between the auxiliary battery and the stack to the auxiliary battery. Charge is transferred BAT1 is greater than the selected termination voltage, the to or from the auxiliary battery when it is connected to a top switches that connect the positive terminal of BAT1 battery in the stack. to the auxiliary batterys positive terminals through the PTC thermistor are turned on. Current is limited by the The LTC3305 can operate in one of two modes, TIMER PTC thermistor. Figure 3 shows the startup battery current mode or CONTINUOUS mode, programmable via the where the PTC is limiting as it heats up. Figure 4 is the MODE pin. Balancing operation begins once the CBOOST steady state battery current after the PTC has reached its capacitor is charged to at least 6.95V. The EN1 and EN2 thermal equilibrium. After a 50ms delay, the termination- pins select the number of batteries in the stack. sense comparator starts to monitor the voltage across the EN1 EN2 Application auxiliary battery and the battery. The battery will remain 0 0 SHUTDOWN connected to the auxiliary battery until the voltage differ- 0 1 2 Battery Stack ence decreases to the selected termination voltage or a 1 0 3 Battery Stack t timeout occurs. BAT 1 1 4 Battery Stack At this point all switches are turned off and the second battery in the stack will be connected to the auxiliary bat- With the MODE pin set to 0 the LTC3305 will operate in tery after a 50ms delay. This 50ms delay provides a break- the TIMER Mode. The BAL pin will be pulled low, indicating before-make function before the next battery is connected. that the part is enabled and balancing the battery stack. The cycle will be repeated for each battery in the stack. The balancing operation begins with the terminal of the Once all batteries in the stack are balanced the DONE pin is auxiliary battery connected to the negative terminal of BAT1, pulled low, the BAL pin is in its high state and the LTC3305 the lowest battery in the stack. The bottom switches that is put into a low power off state. The stack is deemed bal- connect the negative terminals of BAT1 to the auxiliary anced when for a four battery stack, the termination-sense battery s negative terminal are turned on. After a 50ms comparator detects V on five consecutive cycles TERMINATE delay, the voltages across the auxiliary battery and BAT1 that connect each of the batteries to the auxiliary battery are compared by the termination sense comparator. If the using the bottom switches only. dc2043bfb 2