Switch Mode USB Power Manager from Linear Technology

The LTC3566’s PowerPath control feature seamlessly 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, its instant-ON operation ensures power to the system load even with a dead battery. For fast charging, the LTC3566’s switching input stage converts nearly all 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. An internal 180milliohm ideal diode plus optional external ideal diode controller provide a low loss power path from the battery to the system load, further minimizing heat generation and maximizing efficiency.

The LTC3566’s onboard synchronous buck-boost regulator can deliver up to 1A continuously and is ideal for 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 efficiency as high as 94%, maximizing battery run time. In addition, Burst Mode® operation optimizes efficiency at light loads with a quiescent current of only 20uA ( < 1uA in shutdown).

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 LTC3566 features USB-compatible programmable current limiting to 100mA/500mA/1A, while its Bat-Track™ 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 LTC3566 draws only 38uA in suspend mode. The charger is compatible with inputs up to 5.5V (7V absolute maximum transient for added robustness).