LTC4425 Linear SuperCap Charger with Current-Limited Ideal Diode and V/I Monitor Fea T Descrip T n 50m Ideal Diode from V to V The LTC 4425 is a constant-current/constant-voltage linear IN OUT n Smart Charge Current Profile Limits Inrush Current charger designed to charge a 2-cell supercap stack from n Internal Cell Balancer (No External Resistors) either a Li-Ion/Polymer battery, a USB port, or a 2.7V to n Programmable Output Voltage (LDO Mode) 5.5V current-limited supply. The part operates as an ideal n Programmable V to V Current Limit diode with an extremely low 50m on-resistance making IN OUT n Continuous Monitoring of V to V Current via it suitable for high peak-power/low average power ap- IN OUT PROG Pin plications. The LTC4425 charges the output capacitors to n Low Quiescent Current: 20A an externally programmed output voltage in LDO mode at n V Power Fail, PGOOD Indicator a constant charge current, or to V in normal mode with IN IN n 2.45V/2.7V Cell Protection Shunts a smart charge current profile to limit the inrush current (4.9V/5.4V SuperCap Max Top-Off Voltage) until the V to V differential is less than 250mV. In ad- IN OUT n 3A Peak Current Limit, Thermal Limiting dition the LTC4425 can be set to clamp the output voltage n Tiny Application Circuit, 3mm 3mm 0.75mm DFN to 4.9V or 5.4V. and 12-Lead MSOP Packages Charge current (V current limit) is programmed by OUT connecting a resistor between PROG and GND. The volt- a T age on the PROG pin represents the current flowing from n High Peak Power Battery/USB Powered Equipment V to V for current monitoring. An internal active IN OUT n Industrial PDAs balancing circuit maintains equal voltages across each n Portable Instruments/Monitoring Equipment supercapacitor and clamps the peak voltage across each n Power Meters, SuperCap Backup Circuits cell to a pin-selectable maximum value. The LTC4425 n PC Card/USB Modems operates at a very low 20A quiescent current (shutdown L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear current <3A) and is available in a low profile 12-pin Technology Corporation. All other trademarks are the property of their respective owners. 3mm 3mm DFN or a 12-lead MSOP package. Typical a T Charging 2-Cell Series Supercapacitor from Li-Ion Source Charge Current vs V to V Differential IN OUT 0.6 FULL CHARGE CURRENT V = V FB IN V V OUT IN V IN TO HIGH PEAK R = 2k PROG + POWER LOAD 0.5 Li-Ion 2.2F 1.5M 1F 0.4 V MID PFI 1F CURRENT LIMITED 0.3 + V IN BY PMOS RDSON 1.2M FB 0.2 1/10 CHARGE CURRENT 470k PFI RET LTC4425 PFO 0.1 IDEAL DIODE PROG I FORWARD VOLTAGE = 15mV MONITOR SEL 0 2.45V/2.7V FROM 0 0.2 0.4 0.6 0.8 1 C 2k EN V V (V) IN OUT GND 4425 TA02 4425 TA01 4425fa For more information www.linear.com/LTC4425 1 CHARGE CURRENT (A) ion pplica ions pplica ion uresLTC4425 a Te Maxi Mu M r a T (Notes 1, 2) V , V , V , FB, PFI RET, PFO Voltage .0.3V to 6V Storage Temperature Range .................. 65C to 150C IN OUT MID EN, SEL, PFI Voltage ....0.3V to MAX(V , V ) + 0.3V Lead Temperature, MSOP Only IN OUT Operating Junction Temperature ............40C to 125C (Soldering, 10 sec) ................................................300C p in c F T TOP VIEW TOP VIEW V 1 12 V OUT IN 1 V 12 V OUT IN V 2 11 V OUT IN 2 11 V V OUT IN PROG 3 10 V PROG 3 10 V 13 MID 13 MID GND SEL 4 9 PFI GND SEL 4 9 PFI FB 5 8 PFO FB 5 8 PFO EN 6 7 PFI RET EN 6 7 PFI RET MSE PACKAGE DD PACKAGE 12-LEAD PLASTIC MSOP 12-LEAD (3mm 3mm) PLASTIC DFN T = 125C, = 35C/W (Note 3) JMAX JA T = 125C, = 43C/W (Note 3) JMAX JA EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB o r Der i n F Ma T (