The LP3974 is designed to meet the power management requirements of the latest cellular phones. The LP3974 PMU contains a
single-input Li-Ion battery charger, 16 low-dropout voltage regulators (including 5 wide input low-output regulators, 2 over-voltage
protected voltage regulators, and 4 buck regulators), dual DPDT analog switches, real time clock, and backup battery charger.
Programming is handled via an I
2C-compatible high-speed Serial Interface allowing control of program on/off conditions and the output voltages of individual
regulators, and to read status information of the PMU.
It can charge and maintain a single cell Li-Ion battery operating from an AC adapter or USB power source.
The Li-Ion charger requires few external components and integrates the power FET. Charging is thermally regulated to obtain
the most efficient charging rate for a given ambient temperature.
Over-Voltage Protection (OVP) circuit at the charger input protects the PMU from input voltages up to +28V, eliminating the
need for any external protection circuitry.
Buck regulators have an automatic switch to ECO mode at low load conditions providing very good efficiency at low output currents.
General-type LDO regulators provide excellent PSRR and ULTRA LOW NOISE, 45 μV typ., ideally suited for supplying voltage to
The real-time clock/calendar provides time interval information as well as two programmable alarms.
To accommodate different processor requirements, the LP3974 PMU can have three different default voltage settings and startup
sequences selected by external pin.
Notice: This document is not a full datasheet. For more information regarding this product or to order samples please contact
your local National Semiconductor sales office or visit http://www.national.com/support/dir.html
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