Multifunction Switching Power Manager from Linear Technology

The LTC3576 features a bidirectional switching power manager with input overvoltage protection and USB On-The-Go (OTG) functionality, a stand-alone battery charger, three high efficiency synchronous buck regulators, an ideal diode, I2C control, plus an always-on LDO, all in a compact, low-profile 4mm x 6mm QFN package.

The LTC3576’s USB-compatible bidirectional switching regulator features programmable input current limits of 100mA and 500mA, as well as a 1A wall adapter input current limit. For fast charging, the LTC3576 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 from a wall adapter. The bidirectional switching regulator can also take power from the battery to generate 5V and deliver up to 500mA for USB OTG applications without any additional components. The IC provides an overvoltage protection (OVP) control circuit that prevents damage to its input from the accidental application of voltages as high as 66V. The OVP circuit can protect the USB port even when the IC is providing power for USB OTG.

The LTC3576’s PowerPath control with automatic load prioritization seamlessly manages power flow between a variety of input power sources such as a wall adapter or USB port and the Li-Ion/Polymer battery while preferentially providing power to the system load. The IC’s instant-ON operation ensures system load power even with a discharged battery. An internal 180mOhm ideal diode plus optional external ideal diode controller provide a low loss power path from the battery to the load when input power is limited or unavailable.

The LTC3576 provides Bat-Track control of a companion Linear Technology switching regulator for efficient charging from high voltage inputs while minimizing heat dissipation and providing a seamless transition between USB and the higher voltage power source. The LTC3576’s stand-alone battery charger features autonomous operation that simplifies design and eliminates the need for an external microprocessor for charge termination. To preserve battery energy, the LTC3576 draws <30uA from the battery in suspend mode.

The LTC3576’s three integrated synchronous buck regulators feature 100% duty cycle operation and are capable of delivering output currents of 1A/400mA/400mA, respectively, with adjustable output voltages down to 0.8V. The 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 per regulator (<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 LTC3576 is available from stock in a compact, low-profile (0.75mm) 4mm x 6mm 38-lead QFN package.