MAX1874 19-2912 Rev 1 2/07 Dual-Input, USB/AC Adapter, 1-Cell Li+ Charger with OVP and Thermal Regulation General Description Features The MAX1874 charges a single-cell Li+ battery from Charge from USB or AC Adapter both USB and AC adapter sources. It also includes bat- Automatic Switchover to AC Adapter tery-to-input power switchover, so the system can be powered directly from the power source rather than Thermal Limiting Simplifies Board Design from the battery. Small, High-Power 16-Pin Thin QFN Package In its simplest application, the MAX1874 needs no external MOSFET or diodes, and accepts input volt- Input Protection Up to 18V ages up to 6.5V however, DC input overvoltage protec- Soft-Start tion up to 18V can be added with a single SOT PFET. Automatic Battery-to-Input Load Switch On-chip thermal limiting simplifies printed circuit board (PCB) layout and allows optimum charging rate without the thermal limits imposed by worst-case battery and input voltage. When the MAX1874 thermal limit is Ordering Information reached, the charger does not shut down but simply reduces charging current. PIN- PKG PART TEMP RANGE PACKAGE CODE Ambient or battery temperature can be monitored with an external thermistor. When the temperature is out of 16 Thin QFN MAX1874ETE -40C to +85C T1655-2 range, charging pauses. 5mm x 5mm Other features include a CHG output to indicate when battery current tapers below a predetermined level. DC Typical Operating Circuit power-OK (DCOK), USB power-OK (UOK), and power- on (PON) outputs indicate when valid power is present. DC INPUT These outputs drive logic or power-selection MOSFETs DC to disconnect the charging sources from the load and to protect the MAX1874 from overvoltage. MAX1874 PON The MAX1874 contains no logic for communication with DCOK the USB host. It must receive instructions from a local BATT DCLV microcontroller. The MAX1874 is available in a 16-pin Li+ CELL 5mm 5mm thin QFN package and operates over the UOK -40C to +85C temperature range. Applications USB CHG USB INPUT PDAs Cell Phones 500mA USEL Wireless Appliances Digital Cameras 100mA TO REF DCI EN Pin Configuration REGULATOR REF TOP VIEW 16 15 14 13 THRM DCLV 1 12 USB DC 2 11 BYP NTC CHG 3 MAX1874 10 PGND THERMISTOR GND BYP PGND USEL 4 9 REF 567 8 THIN QFN Functional Diagram appears at the end of the data sheet. 5mm x 5mm Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE EN DCOK BATT GND DCI PON THRM UOKDual-Input, USB/AC Adapter, 1-Cell Li+ Charger with OVP and Thermal Regulation ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation (T = +70C) DC, DCOK to GND.................................................-0.3V to +20V A 16-Pin 5mm 5mm Thin QFN DCLV, BYP, USB, UOK, DCI, REF, USEL, THRM, (derate 21.3mW/C above +70C)...................................1.7W EN, BATT, CHG, PON to GND .............................-0.3V to +7V Operating Temperature Range ...........................-40C to +85C PGND to GND .......................................................-0.3V to +0.3V Storage Temperature Range .............................-65C to +150C Continuous Current (DCLV) ..................................................1.1A Maximum Junction Temperature .....................................+150C Continuous Current (USB) ....................................................0.6A Lead Temperature (soldering, 10s) .................................+300C 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 (V = V = V = V = V = 5V, V = 4.2V, V = V / 2, Circuit of Figure 2, T = 0C to +85C, unless otherwise USB DC DCLV EN USEL BATT THRM REF A noted. Typical values are at T = +25C.) A PARAMETER CONDITIONS MIN TYP MAX UNITS INPUT VOLTAGE RANGES AND INPUT CURRENT Maximum DC Input Voltage with Q2 input MOSFET must be in place charging 18 V Overvoltage Protection occurs only below 6.2V, Figures 3, 4, and 5 Maximum DC Input Voltage Without DC = DCLV, Q2 input MOSFET not on circuit, 6.5 V Overvoltage Protection Figure 2 Maximum Input Voltage for Charging 6.0 6.2 6.5 V V = 0V 2 4 EN DC Supply Current mA V = 5V 4 6 EN DCLV Operating Voltage Range 4.35 6.00 V DCLV Shutdown Supply Current V = 0V 300 500 A EN USB Input Voltage Range 4.35 6.50 V V = 0V 500 750 A EN USB Supply Current V = 5V, V = 0V 2 3 mA EN DC V = 5V, V = 5V 160 300 A EN DC DCI Input Current 1 100 nA BYP Output Resistance (Note 1) 5 THRM Input Bias Current 1 100 nA BATTERY VOLTAGE BATT Regulation Voltage 4.1685 4.20 4.2315 V BATT Prequal Voltage Threshold BATT rising 2.8 3 3.2 V Prequal Threshold Hysteresis 70 mV I = 100mA 100 USB USB Charging Headroom mV I = 500mA 200 USB DC Charging Headroom I = 800mA 250 mV DCIN I = 0 to 500A, 4V < V or V < 6.5V REF DC USB REF Voltage (Buffered Output) 2.94 3 3.06 V does not affect BATT regulation accuracy 2 MAX1874