Power management ICs for portable applications

Linear Technology has launched the LTC3577, LTC3577-1, LTC3577-3 and LTC3577-4, highly integrated multi-function power management integrated circuits for portable Li-ion/polymer battery applications.

The LTC3577/-X integrates a USB-compatible linear Powerpath manager, a standalone battery charger, over-voltage protection, 10-LED driver, pushbutton on/off control, three high-efficiency synchronous buck regulators and two LDOs in a low-profile 4 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.

These ICs are said to be suitable for portable device applications including personal navigation devices, digital media/video broadcasting, digital/satellite radio, media players, universal remotes, photo viewers and portable medical and industrial devices.

The LTC3577/-X's Powerpath manager with automatic load prioritisation 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 over-voltage 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 ultra-low quiescent current state that draws <10uA and disables all power supplies and power paths.

The LTC3577/-1 can control an external high-voltage buck regulator to achieve high-efficiency Bat-Track charging and power path control from a high-voltage source, reducing power dissipation.

The internal 200mohm ideal diode, plus an optional external ideal diode controller, provide a low-loss power path to the load when input current is limited or unavailable.

The LTC3577/-X's three integrated synchronous buck regulators feature 100 per cent 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 per cent, further maximising battery run time.

In addition, I2C-controlled Burst Mode operation optimises efficiency at light loads with a quiescent current of only 20uA per regulator (< 1uA in shutdown).

Furthermore, the regulators are stable with ceramic output capacitors, achieving low output voltage ripple.

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 compact, low-profile (0.75mm) 4 x 7mm QFN-44 package.

Back to top