19-0994; Rev 0; 10/07 KIT ATION EVALU E L B AVAILA 28V Linear Li+ Battery Charger with Smart Autoboot Assistant The MAX8814 intelligent, stand-alone constant-current, constant-voltage (CCCV), thermally regulated linear charger is designed for charging a single-cell lithiumion (Li+) battery. The MAX8814 integrates the currentsense circuit, MOSFET pass element, thermalregulation circuitry, and eliminates the reverse-blocking Schottky diode to create the simplest and smallest charging solution for handheld equipment. The IC controls the charging sequence from the prequalification state through constant-current fast-charge and the final constant voltage charge. Proprietary thermal-regulation circuitry limits the die temperature during fast-charging or when the IC is exposed to high ambient temperatures, allowing maximum charging current without damaging the IC. The MAX8814 achieves high flexibility by providing an adjustable fast-charge current through an external resistor. Other features include an active-low control input (EN) and an active-low input power-source detection output (POK). The IC also features a booting assistant circuit that distinguishes input sources and battery connection and provides an output signal (ABO) for system booting. The MAX8814 accepts an input supply range from 4.25V to 28V, but disables charging if the input voltage exceeds +7V to protect against unqualified or faulty AC adapters. The IC operates over the extended temperature range (-40°C to +85°C) and is available in a compact 8-pin thermally enhanced TDFN 2mm x 2mm package (0.8mm max height). Applications Features o CCCV, Thermally Regulated Linear 1-Cell Li+ Battery Charger o No External MOSFET, Reverse Blocking Diode, or Current-Sense Resistor o Programmable Fast-Charge Current (1ARMS max) o Proprietary Die Temperature Regulation Control (+115°C) o 4.25V to 28V Input Voltage Range with Input OVP Above +7V o Charge-Current Monitor for Fuel Gauging (ISET) o Low Dropout Voltage (300mV at 500mA) o Input Power-Source Detection Output (POK), Charge-Enable Input (EN) o Soft-Start Limits Inrush Current o Output for Autobooting (ABO) o Tiny 2mm x 2mm, 8-Pin TDFN Package, 0.8mm Height (max) Ordering Information PART MAX8814ETA+ TEMP RANGE -40°C to +85°C PINPACKAGE PKG CODE TOP MARK 8 TDFN 2mm x 2mm T822+2 ABI +Denotes a lead-free and RoHS-compliant package. Typical Operating Circuit Cellular and Cordless Phones Smartphones and PDAs MP3 Players BATT 4.25V TO 28V Digital Still Cameras + 2.2μF IN Li+ USB Appliances Charging Cradles and Docks Bluetooth® Equipment MAX8814 SYSTEM SUPPLY OFF ON EN ABI ISET GND POK EP ABO Bluetooth is a registered trademark of Bluetooth SIG. Pin Configuration appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX8814 General Description MAX8814 28V Linear Li+ Battery Charger with Smart Autoboot Assistant ABSOLUTE MAXIMUM RATINGS IN to GND ...............................................................-0.3V to +30V ABI, BATT, EN, POK to GND....................................-0.3V to +6V ABO to GND............................................-0.3V to (VBATT + 0.3V) ISET to GND .............................................................-0.3V to +4V IN to BATT Continuous Current .........................................1ARMS Continuous Power Dissipation (TA = +70°C) 8-Pin TDFN (derate 11.9mW/°C above +70°C) (multilayer PCB) ........................................................953.5mW BATT Short-Circuit Duration .......................................Continuous Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = 5V, VBATT = 4V, R POK = 1MΩ to BATT, EN = 0V, RISET = 2.8kΩ to GND, CBATT = 2.2µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS Input Voltage Range Input Operating Voltage Range UNITS 0 28 V 4.25 6.50 V 40 30 Overvoltage-Lockout Trip Threshold VIN rising, 100mV hysteresis (typ) 6.5 7.5 Constant-current charging mode (IBATT = 0A) 0.8 1.35 IC disabled (VEN = 5V) 0.23 0.50 TA = +25°C 0.021 0.065 TA = +85°C 0.021 VIN = 0 to 4V, VBATT = 4.2V 1 IC disabled 3 IBATT = 0A 4.179 4.200 4.221 TA = -40°C to +85°C 4.158 4.200 4.242 2.2 524 570 616 TA = -40°C to +85°C 485 570 656 TA = 0°C to +85°C 89 107 125 TA = -40°C to +85°C 80 107 134 Percentage of the fast-charge current, VBATT = 2.2V, TA = 0°C to +85°C 4 10 15 Fast-Charge Current VBATT = 3.5V, RISET = 14kΩ Die Temperature Regulation Threshold +115 VBATT Prequalification Threshold Voltage VBATT rising, 100mV hysteresis (typ) Current-Sense Amplifier Gain (IBATT to IISET) IBATT = 570mA 2.3 2.5 877.2 _______________________________________________________________________________________ V mA µA V µF TA = 0°C to +85°C VBATT = 3.5V 2 10 TA = 0°C to +85°C Minimum BATT Bypass Capacitance Prequalification Charge Current mV 7 VIN = 4V, VBATT = 4.2V Battery Regulation Voltage MAX VIN falling VIN - VBATT, 10mV hysteresis (typ) BATT Input Current TYP VIN rising Power-OK Threshold IN Input Current MIN mA % °C 2.7 V µA/A 28V Linear Li+ Battery Charger with Smart Autoboot Assistant (VIN = 5V, VBATT = 4V, R POK = 1MΩ to BATT, EN = 0V, RISET = 2.8kΩ to GND, CBATT = 2.2µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS Regulator Dropout Voltage (VIN - VBATT ) VBATT = 4.1V, IBATT = 425mA EN Logic-Input Low Voltage 4.25V < VIN < 6.5V EN Logic-Input High Voltage 4.25V < VIN < 6.5V MIN MAX UNITS 240 500 mV 0.4 1.3 EN and ABI Internal Pulldown Resistance 100 ABI Logic-Input Low Voltage VIN = 0V ABI Logic-Input High Voltage VIN = 0V ABO Output Low Voltage IABO (SINK) = 1mA ABO Output High Voltage IABO (SOURCE) = 1mA POK Output Low Voltage I POK = 5mA POK Output High Leakage Current TYP 200 400 0.4 1.3 kΩ V V 0.4 VBATT 0.4V V V 0.4 V POK = 5.5V V V TA = +25°C 0.001 TA = +85°C 0.002 1 V µA Note 1: Specifications are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design and characterization. Typical Operating Characteristics (VIN = 5V, VBATT = 4V, R POK = 1MΩ to BATT, EN = 0V, RISET = 2.8kΩ to GND, CBATT = 2.2µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) SUPPLY CURRENT vs. VOLTAGE 0.7 0.6 0.5 0.4 0.3 600 500 400 300 200 0.2 0.1 100 0 0 0 4 8 12 16 20 INPUT VOLTAGE (V) 24 28 1000 MAX8814 toc03 700 SUPPLY CURRENT (μA) SUPPLY CURRENT (mA) 0.8 VEN = 5V 900 800 CHARGE CURRENT (mA) 0.9 800 MAX8814 toc02 EN = 0V MAX8814 toc01 1.0 CHARGE CURRENT vs. BATTERY VOLTAGE DISABLED MODE SUPPLY CURRENT vs. INPUT VOLTAGE 700 600 500 400 300 200 100 0 0 5 10 15 20 INPUT VOLTAGE (V) 25 30 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 BATTERY VOLTAGE (V) _______________________________________________________________________________________ 3 MAX8814 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VIN = 5V, VBATT = 4V, R POK = 1MΩ to BATT, EN = 0V, RISET = 2.8kΩ to GND, CBATT = 2.2µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) CHARGE CURRENT vs. INPUT VOLTAGE HEADROOM CHARGE CURRENT vs. INPUT VOLTAGE 800 700 600 500 400 300 MAX8814 toc06 MAX8814 toc05 900 900 800 VBATT = 2V VIN 100mA/div 0A 5V/div 0V VEN 5V/div IBATT 700 600 500 400 300 0V 200 200 100 100 0 0 8 12 16 20 24 28 0 100 INPUT VOLTAGE (V) 200 300 400 5V/div 0V VPOK 500 40μs/div VIN - VBATT (mV) BATTERY REGULATION VOLTAGE ACCURACY vs. AMBIENT TEMPERATURE IBATT 500mA/div 0A 5V/div VIN 0V 5V/div VEN 0V 5V/div 0V VPOK 1.0 IBATT = 0A 0.8 0.6 0.4 0.2 0 -0.2 -0.4 100 10 -0.6 -0.8 1 -1.0 -40 100μs/div CHARGE CURRENT vs. RISET 1000 CHARGE CURRENT (mA) MAX8814 toc07 BATTERY REGULATION VOLTAGE ACCURACY (%) SHUTDOWN (FAST-CHARGE TO SHUTDOWN) MAX8814 toc09 4 VBATT = 4V VIN RISING MAX8814 toc08 0 CHARGE CURRENT vs. AMBIENT TEMPERATURE -15 10 35 60 85 1 10 100 RISET (kΩ) AUTOBOOT ENABLED BY ABI SIGNAL AUTOBOOT ENABLED BY INPUT SUPPLY 600 MAX8814 toc10 VBATT = 4V VBATT = 3.2V 5V/div VABI 0V 5V/div 5V/div 400 VIN 10,000 MAX8814 toc12 5V/div 0V VABI 500 1000 TEMPERATURE (°C) MAX8814 toc11 700 CHARGE CURRENT (mA) STARTUP INTO PRECHARGE 1000 MAX8814 toc04 1000 CHARGE CURRENT (mA) CHARGE CURRENT (mA) MAX8814 28V Linear Li+ Battery Charger with Smart Autoboot Assistant 0V VIN 0V 300 VBATT 5V/div 200 VBATT 5V/div 0V 100 0V VABO -15 10 35 60 5V/div 5V/div RISET = 2.8kΩ 0 -40 0V 85 4μs/div 0V VABO 4μs/div TEMPERATURE (°C) 4 _______________________________________________________________________________________ 28V Linear Li+ Battery Charger with Smart Autoboot Assistant PIN NAME FUNCTION 1 IN Input Supply Voltage. Bypass IN to GND with a 1µF or larger ceramic capacitor to minimize line noise and maximize input transient rejection. 2 GND Ground. Connect GND and the exposed paddle to a large copper ground plane for maximum power dissipation. Connect GND to the exposed paddle directly under the IC. 3 ISET Charge-Current Program and Fast-Charge Current Monitor. Output current from ISET is 877.2µA per ampere of battery charging current. Set the charging current by connecting a resistor (R2 in Figure 3) from ISET to GND. IFAST-CHARGE = 1596V / RISET. To configure the MAX8814 as a USB charger, see Figure 4. 4 ABI Autobooting External Input. See the Autobooting Assistant section and Table 1 for autobooting conditions. ABI is pulled to GND through an internal 200kΩ resistor. 5 ABO Autobooting Logic Output. See the Autobooting Assistant section and Table 1 for autobooting conditions. 6 EN 7 POK Input-Voltage Status Indicator. Connect a 1MΩ pullup resistor from POK to an external system supply. POK is an open-drain output that asserts low when VIN > 4.25V and (VIN - VBATT) ≥ 40mV. If VBATT ≥ (VIN - 40mV), the IC is shut down and POK becomes high impedance. 8 BATT Battery Connection. Bypass BATT to GND with a minimum of 2.2µF of capacitor. — EP Logic-Level Enable Input. Drive EN high to disable charger. Drive EN low or leave unconnected for normal operation. EN has an internal 200kΩ pulldown resistor. Exposed Paddle. Connect the exposed paddle to a large ground plane for maximum power dissipation. Connect GND to the exposed paddle directly under the IC. _______________________________________________________________________________________ 5 MAX8814 Pin Description MAX8814 28V Linear Li+ Battery Charger with Smart Autoboot Assistant 4.25V TO 28V BATT IN C1 1μF C3 2.2μF Li+ +115°C OUTPUT DRIVER, CURRENT SENSE, AND LOGIC TEMPERATURE SENSOR ISET R2 2.8kΩ VI/O IN VREF VREF R3 1MΩ POK VIN OVLO VL REGULATOR BATT BATT VL VL UVLO ABO REF VREF ABI REFOK POK 200kΩ LOGIC EN MAX8814 200kΩ GND EP Figure 1. Functional Diagram Detailed Description The MAX8814 charger uses voltage, current, and thermal-control loops to charge a single Li+ cell and protect the battery (Figure 1). When a Li+ battery with a cell voltage below 2.5V is inserted, the MAX8814 charger enters the prequalification stage where it precharges that cell with 10% of the user-programmed fast-charge current (Figure 2). When the battery voltage exceeds 2.5V, the charger soft-starts as it enters the fast-charge stage. In the MAX8814, the fast-charge current level is programmed through a resistor from ISET to GND. As the battery voltage approaches 4.2V, 6 the charging current is reduced. Once the battery voltage reaches 4.2V, the IC then enters a constant voltage regulation mode to maintain the battery at full charge. Thermal Regulation The thermal-regulation loop limits the MAX8814 die temperature to +115°C by reducing the charge current as necessary. This feature not only protects the IC from overheating, but also allows a higher charge current without risking damage to the IC. _______________________________________________________________________________________ 28V Linear Li+ Battery Charger with Smart Autoboot Assistant VBATT < 2.5V (VIN - VBATT) < 30mV PRECHARGE 10% CHARGE CURRENT VIN < 7V, AND (VIN - VBATT) ≥ 40mV, AND IC ENABLED MAX8814 SHUTDOWN CHARGER = DISABLED ASYNCHRONOUS FROM ANYWHERE VIN > 7V, OR (VIN - VBATT) < 30mV, OR IC DISABLED VIN > 7V, OR (VIN - VBATT) < 30mV, OR IC DISABLED VBATT < 2.4V VBATT ≥ 2.5V FAST-CHARGE CONSTANT-CURRENT CHARGE 100% CHARGE CURRENT VBATT ≥ 4.2V VOLTAGE REGULATION CONSTANT VOLTAGE CHARGE REGULATED 4.2V AT BATT VBATT < 4.2V Figure 2. Charge-State Diagram Charger Enable Input The MAX8814 contains an active-low logic input (EN) used to enable the charger. Drive EN low, leave unconnected, or connect to GND to enable the chargercontrol circuitry. Drive EN high to disable the chargercontrol circuitry. EN has an internal 200kΩ pull-down resistor. Table 1. ABO and POK States ABI BATT POK CHARGER STATE ABO Low Present Hi-Z Shutdown Low High Present Hi-Z Shutdown High High High X Not present Low Fast-charge/voltage regulation X Present Low Fast-charge/voltage regulation POK Output The open-drain POK output asserts low when VIN ≥ 4.25V and (VIN - VBATT) ≥ 40mV (typ, VIN rising). POK requires an external pullup resistor (1MΩ typ) to an external power supply. POK is high impedance when VBATT ≥ (VIN - 40mV). Autobooting Assistant The MAX8814 contains an autobooting assistant circuit that generates an enable signal for system booting (ABO). The booting assistant functions as an internal “OR” gate (Figure 1). The first input is dependent on the input voltage (V IN), and the second input is an external signal applied to ABI. The first input (POK) is driven high once VIN ≥ 4.25V and (VIN - VBATT) ≥ 40mV (typ, VIN rising). The second input signal (ABI) is driven by an external source. ABI enables an autoboot signal (ABO high) when a battery is connected at BATT and is independent of POK. If POK is pulled low, the booting assistant always drives ABO high, regardless of ABI (see Table 1). ABI is pulled to GND through an internal 200kΩ resistor. X = Don’t care. If ABI is driven externally, a RC filter (R1 and C2 of Figure 3) is required for ESD protection and noise filtering. If ABI is supplied by a system’s internal GPIO, or logic, the RC filter is not required. Soft-Start The soft-start algorithm activates when entering fastcharge mode. In the MAX8814, when the prequalification state is complete (V BATT ≥ 2.5V), the charging current ramps up in 250µs to the full charging current. This reduces the inrush current on the input supply. _______________________________________________________________________________________ 7 MAX8814 28V Linear Li+ Battery Charger with Smart Autoboot Assistant FACTORY TEST FIXTURE OR AC ADAPTER C1 1μF BATT IN C3 2.2μF SYSTEM R1 10kΩ ABI VI/O MAX8814 C2 0.1μF GND Li+ R3 1MΩ POK GPIO EN GPIO ABO GND EP ISET R4 10kΩ ADC R2 2.8kΩ C4 0.1μF POWER SUPPLY ON Figure 3. Microprocessor-Interfaced Li+ Battery Charger Applications Information Charge-Current Selection The maximum charging current is programmed by an external resistor connected from ISET to GND (RISET). Calculate RISET as follows: R ISET = 1596V I FAST−CHARGE where I FAST-CHARGE is in amperes and R ISET is in ohms. ISET can be used to monitor the fast-charge current level. The output current from ISET is 877.2µA per ampere of charging current. The output voltage at ISET is proportional to the charging current: I × R ISET V ISET = CHARGE 1140 The voltage at ISET is nominally 1.4V at the selected fast-charge current and falls with charging current as the cell becomes fully charged or as the thermal-regulation circuitry activates. 8 Capacitor Selection Connect a ceramic capacitor from BATT to GND for proper stability. Use a 2.2µF X5R ceramic capacitor for most applications. Connect a 1µF ceramic capacitor from IN to GND. Use a larger input bypass capacitor for high charging currents to reduce supply noise. Thermal Considerations The MAX8814 is available in a thermally enhanced TDFN package with an exposed paddle. Connect the exposed paddle to a large copper ground plane to provide a thermal contact between the device and the circuit board for increased power dissipation. The exposed paddle transfers heat away from the device, allowing the IC to charge the battery with maximum current, while minimizing the increase in die temperature. DC Input Sources The MAX8814 operates from a well-regulated DC source. The full charging input voltage range is 4.25V to 7V. The device can withstand up to 28V on the input without damage to the IC. If VIN is greater than 7V, the internal overvoltage-protection circuitry disables charging until the input falls below 7V. An appropriate power supply must provide at least 4.25V at the desired peak charging current. _______________________________________________________________________________________ 28V Linear Li+ Battery Charger with Smart Autoboot Assistant C1 1μF MAX8814 VBUS BATT IN + C3 2.2μF Li+ SYSTEM USB PORT ABI VI/O MAX8814 GND R3 1MΩ GPIO POK ABO GPIO EN GND EP R4 10kΩ ISET ADC R5 4.99kΩ R2 15.8kΩ N C4 0.1μF GPIO POWER SUPPLY ON Figure 4. USB Battery Charger Application Circuits Layout and Bypassing Microprocessor-Interfaced Charger Figure 3 shows the MAX8814 as a microprocessorcooperated Li+ battery charger. The MAX8814 begins charging the battery when EN is low. The microprocessor can drive EN high to disable the charger. The MAX8814 generates a POK signal to indicate the presence of an input supply. By monitoring VISET, the system can measure the charging current and decide when to terminate the charge. Place the input and output capacitors as close as possible to the IC. Provide a large copper ground plane to allow the exposed paddle to sink heat away from the IC. Connect the battery to BATT as close as possible to the IC to provide accurate battery voltage sensing. Make all high-current traces short and wide to minimize voltage drops. A sample layout is available in the MAX8814 Evaluation Kit to speed designs. USB-Powered Li-Ion Charger The universal serial bus (USB) provides a high-speed serial communication port as well as power for the remote device. The MAX8814 can be configured to charge a battery at the highest current possible from the host port. Figure 4 shows the MAX8814 as a USB battery charger. To make the circuit compatible with either 100mA or 500mA USB ports, the circuit initializes at 100mA charging current. The microprocessor then enumerates the host to determine its current capability. If the host port is capable, the charging current is increased to 425mA to avoid exceeding the 500mA USB specification. PROCESS: BiCMOS Chip Information _______________________________________________________________________________________ 9 28V Linear Li+ Battery Charger with Smart Autoboot Assistant MAX8814 Pin Configuration TOP VIEW BATT POK EN ABO 8 7 6 5 MAX8814 EXPOSED PADDLE + 1 2 3 4 IN GND ISET ABI TDFN 2mm x 2mm 10 ______________________________________________________________________________________ 28V Linear Li+ Battery Charger with Smart Autoboot Assistant 8L TDFN EXPOSED PADS.EPS PACKAGE OUTLINE 6 & 8L TDFN EXPOSED PAD, 2x2x0.80mm 21-0168 D 1 2 ______________________________________________________________________________________ 11 MAX8814 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) MAX8814 28V Linear Li+ Battery Charger with Smart Autoboot Assistant Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) COMMON DIMENSIONS SYMBOL A MIN. MAX. 0.70 0.80 D 1.90 2.10 E 1.90 2.10 A1 0.00 0.05 L 0.20 0.40 k 0.25 MIN. A2 0.20 REF. PACKAGE VARIATIONS PKG. CODE N D2 E2 e b r [(N/2)-1] x e T622-1 6 0.90±0.10 1.60±0.10 0.65 TYP. 0.30±0.05 0.150 1.30 REF T822-1 8 0.70±0.10 1.30±0.10 0.50 TYP. 0.25±0.05 0.125 1.50 REF T822-2 8 0.80±0.10 1.20±0.10 0.50 TYP. 0.25±0.05 0.125 1.50 REF PACKAGE OUTLINE 6 & 8L TDFN EXPOSED PAD, 2x2x0.80mm 21-0168 D 2 2 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.