PMICs deliver improved battery cycle life

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 R_DS(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.