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PMICs deliver improved battery cycle life

Posted: 06 Aug 2009 ?? ?Print Version ?Bookmark and Share

Keywords:power management IC? PMIC? battery?

Linear Technology Corp. has released a series of highly integrated multi-function power management integrated circuit (PMIC) solutions for portable Li-ion or polymer battery applications. The LTC3577/-X integrates USB-compatible linear PowerPath manager, standalone battery charger, overvoltage protection (OVP), 10-LED driver, pushbutton on/off control, three high efficiency synchronous buck regulators and two LDOs, all in a low-profile 4mm x 7mm QFN package.

The LTC3577-1 and LTC3577-4 feature a 4.1V battery float voltage for improved battery cycle life and additional high temperature safety margin, while the LTC3577 and LTC3577-3 include a standard 4.2V battery float voltage for maximum run time. The LTC3577-3 and LTC3577-4 are tailored for SiRF Atlas IV chipsets.

The LTC3577/-X's PowerPath manager with automatic load prioritization seamlessly manages the transition between multiple input sources to power the load, while delivering up to 1.5A battery charge current from a wall adapter supply or up to 500mA charge current from a USB port. The charger is compatible with inputs up to 5.5V (7V absolute maximum transient for added robustness). The ICs "instant-on" operation ensures system load power even with a fully discharged battery. Autonomous operation simplifies design, eliminating the need for an external microprocessor for charge termination. An overvoltage protection controller enables up to 30V protection for the Wall/USB input, while a high temperature battery voltage reduction circuit improves battery safety and reliability.

To preserve battery energy during long periods of inactivity or to reset the product in the event of a software lockup, the LTC3577/-1 contains a hard reset function enabled via pushbutton control, placing the IC into an ultralow quiescent current state that draws The LTC3577/-X's three integrated synchronous buck regulators feature 100 percent duty cycle operation and are capable of delivering output currents of 800-/500-/500mA respectively, with adjustable output voltages down to 0.8V. A high 2.25MHz switching frequency allows the use of tiny low cost capacitors and inductors less than 1mm in height. Internal low RDS(ON) switches enable efficiencies as high as 95 percent, further maximizing battery runtime. In addition, I2C-controlled Burst Mode operation optimizes efficiency at light loads with a quiescent current of only 20?A per regulator (Additional features of the LTC3577/-X include a 40V series backlight 10-LED driver with I2C controlled 60dB brightness (1000:1 dimming range) and gradation control, pushbutton on/off control with system reset, and dual 150mA current limited LDOs.

The LTC3577/-X is available from stock in a QFN-44 package. Pricing starts at $4.95 each for 1,000-piece quantities.

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