Linear Technology Corp.'s LTC3554 micropower multifunction power management integrated circuit (PMIC) solution for portable Li-Ion/Polymer battery-based applications integrates a USB-compatible linear PowerPath manager, a stand-alone battery charger, two high efficiency synchronous buck regulators and pushbutton control in an ultra-thin (0.55mm) 3x3mm QFN package. A pin-selectable standby mode reduces battery drain current to just 10µA 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 0.4A 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 240mΩ 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 percent duty cycle operation and are capable of delivering output currents of 0.2A 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 percent, further maximizing battery run time. In addition, Burst Mode operation optimizes efficiency at light loads with a quiescent current of only 25µA per regulator (<1µA 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 (<1µA) Hard Reset state, saving battery run time.
Linear Technology's LTC3554 Micropower USB Power Manager with Li-Ion Charger and Two Step-down Regulators
Linear Technology
