Linear Technology has introduced the LTC3567, the latest in a family of multi-function power management solutions for Li-Ion/Polymer battery applications.
Integrating a switching PowerPath manager, a stand-alone battery charger, a 1A high efficiency synchronous buck-boost regulator, an ideal diode and controller, I2C control, plus an always-on LDO, the LTC3567 packs a lot into its low-profile 4mm x 4mm QFN package.
The PowerPath control feature manages power flow between multiple input sources, such as a wall adapter or USB port and the Lithium battery while preferentially providing power to the system load. In addition, 'instant-ON' operation ensures power to the system load even with a depleted battery. Enabling fast charging, the LTC3567's switching input stage converts much of the 2.5W available from the USB port to charging current, enabling up to 700mA from a 500mA limited USB supply and up to 1.5A when wall powered. The internal 180milliohm ideal diode and optional external ideal diode controller provide a low loss power path from the battery to the system load, minimising heat generation and maximising efficiency.
The LTC3567's onboard synchronous buck-boost regulator delivers up to 1A continuously, making the device capable of efficiently regulating a 3.3V output voltage over the full Lithium battery voltage range, down to 2.75V input. The regulator's internal low RDS(ON) switches enable high efficiency (up to 94%), whilst Burst Mode operation optimises efficiency at light loads, resulting in a claimed quiescent current of just 20uA. The high 2.25MHz switching frequency allows the use of tiny low cost capacitors and inductors less than 1mm in height. Furthermore, the regulators are stable with ceramic output capacitors, achieving very low output voltage ripple.
The LTC3567 features USB-compatible programmable current limiting to 100mA/500mA/1A, and adaptive output control enables high efficiency battery charging and reduces power dissipation. Stand-alone autonomous operation simplifies design, eliminating the need for an external microprocessor for battery charge termination. To preserve battery energy, the LTC3567 draws only 38uA in suspend mode. The charger is compatible with inputs up to 5.5V.