USB Power Manager & Dual Buck PMIC Optimized for Ultralow IQ

A pin-selectable standby mode reduces battery drain current to just 10uA with all outputs on. The LTC3554 is well suited for low power portable device applications, including personal navigation devices (PNDs), media players and handheld medical and industrial devices.

The LTC3554's PowerPath manager with automatic load prioritization seamlessly manages the transition between multiple input sources to power the load, while delivering up to 400mA battery charge current from a USB port or 5V wall adapter supply. The input current limit is pin-selectable and internally set (no external resistor is required). The LTC3554 is compatible with inputs up to 5.5V (7V absolute maximum transient for added robustness). The device's 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. The internal 240mOhm ideal diode provides a low loss power path to the load when input current is limited or unavailable. An NTC function is onboard for temperature-qualified charging.

The LTC3554's two integrated synchronous buck regulators feature 100% duty cycle operation and are capable of delivering output currents of 200mA each, with adjustable output voltages down to 0.8V. For flexibility, the regulators may be enabled and disabled independently. The oscillator frequency and corresponding patented slew rate circuitry are pin-selectable (1.125MHz or 2.25MHz), allowing the application circuit to dynamically trade off efficiency and EMI performance. The high switching frequencies also allow the use of tiny low cost capacitors and inductors less than 1mm in height. Internal low RDS(ON) switches enable efficiencies as high as 93%, further maximizing battery run time. In addition, Burst Mode® operation optimizes efficiency at light loads with a quiescent current of only 25uA per regulator (<1uA in shutdown). Furthermore, the regulators are stable with ceramic output capacitors, achieving very low output voltage ripple. The integrated pushbutton controller provides buck regulator sequencing and access to an ultralow current (<1uA) Hard Reset state, saving battery run time.