![]() The LTC3557 takes over the control of buck regulator via the V C pin and sets the V OUT pin voltage at a fixed offset above the battery voltage. The input supply range can be expanded by using an appropriate high voltage buck regulator as shown in Figure 1. Alternatively, power can be directly provided to the system load (V OUT) via an external PFET connected in series with an AC wall adapter. The 1A (10x) mode is reserved for use with a higher current input power supply such as an AC wall adapter. Table 2 shows the different operating modes of the input current limit. The programmable current limit is set by a single external resistor (R CLPROG) on the CLRPOG pin and the logic state of ILIM0 and ILIM1 pins. The LTC3557 can derive power from a current limited input such as USB. Ultra low quiescent current 3.3V LDO for real time clock, standby power, pushbutton control, etc. Power on Reset output for power sequencing. User-programmable output voltages with external resistor divider. Internally compensated to save valuable board space. High frequency switching (2.25MHz) stays out of the AM band and enables use of tiny inductors. Three High Efficiency Step-Down Switching Regulators Preset float voltage accurate to 0.85%.ĭisables charging of the battery under extreme temperature conditions outside a programmable rangeįour modes of CHRG pin including ON, OFF, Slow Blink and Fast Blink to report various operating states Uses constant current/constant voltage architecture with thermal regulation for optimal charging. The Bat-Track feature allows efficient charging of the battery to minimize heat dissipation in the application High Voltage Buck Control with Bat-Track ™Ĭontrols external HV buck to expand input voltage range up to 38V. Precision input current limit which communicates with the battery charger to ensure that input current never violates the USB specification Provides power from 5V wall adapter directly to system load through an external low impedance PFET Features of the LTC3557 FeatureĪllows seamless transition between input power sources (Li-Ion battery, USB, wall adapter or high voltage buck regulator) to supply system load. Table 1 highlights some of the key features of the LTC3557. The LTC3557 is a highly integrated power management and battery charger IC for single cell Li-Ion/Polymer battery applications. It combines a full featured USB power manager, a Li-ion battery charger, three high frequency step-down switching regulators and a 3.3V always-on LDO in a single 4mm × 4mm QFN package. The LTC3557 solves this problem by bringing all power management functions into a single device. If each of these functions is served by a separate power supply IC, each IC (and its external components) occupies valuable board space, consumes battery-draining quiescent current and significantly increases the overall development and material costs of the device. Modern, feature-rich handheld and portable devices require several power management circuits, including a battery charger, multiple step-down switching regulators and low power LDOs for watchdog circuitry. Mobile technology has radically changed the way we acquire, share and disseminate information. Highly Integrated USB Power Manager with Li-Ion Charger and Three Step-Down Switching Regulators in 4mm × 4mm QFN
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