DEMO MANUAL DC1688A LT3652HVEDD 17.7V to 34V Input SLA 2A Battery Charger For Solar Power DESCRIPTION Demonstration circuit 1688A is a sealed-lead acid 2A programmed by a current sense resistor. A precondition battery charger for solar power applications featuring the feature trickle charges a low voltage battery, and bad LT3652HVEDD. The LT3652HV is a complete mid-power battery detection provides a signal if the battery doesnt battery charger that can operate over a wide input volt- respond to preconditioning. age range. The charger employs a 3.3V battery voltage The LT3652HVEDD is available in a 12-lead (3mm 3mm) feedback reference that allows the voltage for charging to DFN surface mount package with an exposed pad. be adjusted up to 18V. The LT3652HV has an input voltage regulation loop which reduces charge current if the input Design les for this circuit board are available at falls below a programmed level, set with a resistor divider. DEMO MANUAL DC1688A OPERATING PRINCIPLE resistor, R . Once the battery voltage increases to triggers a system fault if a battery stays in precondition SENSE the precondition threshold, the IC automatically increases mode for more than 1/8th of the total charge cycle time. maximum charging current to the full programmed value. Once charging is terminated and the LT3652HV is not DC1688A programs the output voltage to be 14.4V during actively charging, the IC automatically enters a low current charging and the 9.5V precondition threshold is internally standby mode where supply bias currents are reduced to set as a fraction of the programmed output voltage. < 100A. If the battery voltage drops 2.5% from the full- The LT3652HV can use a charge current based C/10 charge oat voltage, the LT3652HV engages an automatic termination scheme, which ends a charge cycle when the charge cycle restart. The IC also automatically restarts a battery charge current falls to 1/10th the programmed new charge cycle after a bad battery fault once the failed maximum charge current. The LT3652HV also contains battery is removed and replaced with another battery. an internal charge cycle control timer, for timer-based The LT3652HV includes provisions for a battery tem- termination. When using the internal timer, the IC com- perature monitoring circuit. This feature monitors battery bines C/10 detection with a programmable time constraint, temperature during the charging cycle using a thermistor, during which the charging cycle can continue beyond the and suspends charging and signals a fault condition if the C/10 level. DC1688A programs a lower 13.5V oat output battery temperature moves outside a safe charging range voltage at the time the C/10 condition occurs. Use of the of 0C to 50C. internal timer allows DC1688A to provide a oat voltage The LT3652HV contains two digital open-collector outputs, to the battery until the charge cycle terminates because which provide charger status and signal fault conditions. time elapses. The timer on DC1688A is programmed so the These binary-coded pins signal battery charging, standby circuit can provide a oat voltage all day, as may be needed or shutdown modes, battery temperature faults, and bad by a solar panel application. When the timer-based scheme battery faults. is used, the IC also supports bad battery detection, which 90 2.0 2.5 V = 12V I = 2A BAT IN 1.8 V = 15V IN V = 24V IN 1.6 2.0 85 1.4 1.2 1.5 80 1.0 0.8 1.0 0.6 75 0.4 0.5 V = 12V IN V = 15V IN 0.2 V = 24V IN 70 0.0 0.0 3.3 4.5 5.7 6.9 8.1 9.3 10.5 11.7 12.9 14.1 3.3 4.5 5.7 6.9 8.1 9.3 10.5 11.7 12.9 14.1 17.5 17.6 17.7 17.8 17.9 18 18.1 18.2 18.3 BATTERY VOLTAGE BATTERY VOLTAGE INPUT VOLTAGE 1688A F01 1688A F02 1688A F03 Figure 1. LT3652HV Ef ciency Figure 2. 2A Charge Current Figure 3. Charge Current vs Input Voltage QUICK START PROCEDURE Demonstration circuit 1688A is easy to set up to evaluate Using short twisted pair leads for any power connections, the performance of the LT3652HVEDD. with all loads and power supplies off, refer to Figure 4 for the proper measurement and equipment setup. dc1688afa 2 EFFICIENCY INPUT CURRENT CHARGE CURRENT (A)