DEMO CIRCUIT 1473A LT3650EDD-8.4/8.2 QUICK START GUIDE LT3650EDD-8.4/8.2 2A Monolithic Li-Ion Battery Charger DESCRIPTION Demonstration Circuit 1473A is a 2A Monolithic Li-Ion (3mm 3mm) DFN surface mount package with an Battery Charger featuring the LT3650EDD-8.4/8.2. The exposed pad. LT3650 is a complete mid-power Li-Ion battery Design files for this circuit board are available. Call charger that can operate over a wide input voltage the LTC factory. range. The charger is a CC/CV charger with a maxi- L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered mum charge current externally programmable up to trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode 2A. A precondition feature trickle charges a low- Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelProtect, SENSE voltage battery and bad battery detection provides a PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names signal if the battery doesnt respond to precondition- may be trademarks of the companies that manufacture the products. ing. The LT3650EDD-8.4/8.2 is available in a 12-lead Table 1: Typical Specifications (25C) HV Input Voltage Range 9V to 32V VOUT 7.4V to 8.48V Output Float Voltage (constant voltage mode) 8.4V/8.2V Output Current Limit ILIM 2A (R equals 20k) RNG OPERATING PRINCIPLE LT3650 is a complete monolithic mid-power Li-Ion bat- The LT3650 incorporates several degrees of charge cur- tery charger, addressing high input voltage applications rent control freedom. The overall maximum charge cur- with solutions that require a minimum of external com- rent is set using an external inductor current sense resis- ponents. The IC uses a 1MHz constant frequency, aver- tor. A maximum charge current programming pin allows age-current mode step-down architecture. dynamic manipulation of the battery charge current. The LT3650 also incorporates a system input-supply current The LT3650 incorporates a 2A switch that is driven by a limit control feature that servos the battery charge cur- bootstrapped supply to maximize efficiency during rent to accommodate overall system load requirements. charging cycles. A wide input range allows operation to The LT3650 automatically enters a battery precondition fully charge from 10V +/- 5% (single cell) to 32V. A pre- mode if the sensed battery voltage is very low. In this cision-threshold shutdown pin allows the incorporation mode, the charging current is reduced to 15% of the of UVLO functionality using a simple resistor-divider. programmed maximum, as set by the inductor sense The IC can also be put into a low-current shutdown resistor, R . Once the battery voltage climbs above an SENSE mode, in which the input supply bias is reduced to only internally set threshold of 5.7V / cell, the IC automatically 15uA. 1 LT3650EDD-8. 4/8.2 increases maximum charging current to the full pro- standby mode where supply bias currents are reduced to grammed value. < 100uA. If the battery voltage drops 2.5% from the full- The LT3650 can use a charge-current based C/10 ter- charge float voltage, the LT3650 engages an automatic mination scheme, which ends a charge cycle when the charge cycle restart. The IC also automatically restarts a th battery charge current falls to 1/10 the programmed new charge cycle after a bad battery fault once the failed maximum charge current. The LT3650 also contains an battery is removed and replaced with another battery. internal charge cycle control timer, for timer-based ter- The LT3650 includes provisions for a battery tempera- mination. When using the internal timer, the IC com- ture monitoring circuit. This feature monitors battery bines C/10 detection with a programmable time con- temperature during the charging cycle using a thermis- straint, during which the charging cycle can continue tor, and suspends charging and signals a fault condition beyond the C/10 level to top-off a battery. The charge if the battery temperature moves outside a safe charging O O cycle terminates when a specific time elapses, typically 3 range of 0 C to 50 C. hours. When the timer-based scheme is used, the IC The LT3650 contains two digital open-collector outputs, also supports bad-battery detection, which triggers a which provide charger status and signal fault conditions. system fault if a battery stays in precondition mode for These binary-coded pins signal battery charging, standby th more than 1/8 of the total charge cycle time. or shutdown modes, battery temperature faults, and bad Once charging is terminated and the LT3650 is not ac- battery faults. tively charging, the IC automatically enters a low-current QUICK START PROCEDURE Demonstration circuit 1473A is easy to set up to evaluate 3. Verify that the battery charging current, IBAT, is the performance of the LT3650EDD-8.4/8.2. between 250mA and 350mA. The CHRG LED should be on and the FAULT LED should be off. Using short twisted pair leads for any power connec- tions, with all loads and power supplies off, refer to 4. Increase PS2 until VBAT is 7.2V. Verify the input Figure 1 for the proper measurement and equipment current, IIN, is between 1.3A and 1.7A, the battery setup. current, IBAT, is between 1.775A and 2.225A and that the CHRG LED is on. Follow the procedure below: 5. Increase PS2 until VBAT is 8.5V. Verify the battery 1. Jumper and Power Supply Setting: charging current, IBAT, is less than 5mA and that JP1 = 1 PS1 = OFF the CHRG LED is off. JP2 = 1 PS2 = OFF 6. Decrease PS2 until VBAT is 7.8V. Verify the bat- JP3=C/10 tery current, IBAT, is between 1.775A and 2.225A that the CHRG LED is on. 2. Turn on PS2 and slowly increase the voltage to 5.4V while monitoring the current into the BAT 7. Decrease PS2 until VBAT is 7.2V. Connect a 10K pin. If the current is less than 5mA, turn on PS1. resistor from the RNG/SS pin to ground. Verify the Increase the voltage on PS1 to 5V while monitor- charging current, IBAT, is between 850mA and 1.1A. Verify the voltage, VNTC, on the NTC turret ing the input current. If the current is less than 5mA, increase PS1 to 12V. is between 450mV and 550mV and the voltage, 2