Datasheet

VIN
ENLDO
VLDO
GND
+
-
V
REF
LDO_FB
LM26480
www.ti.com
SNVS543I JANUARY 2008REVISED MAY 2013
DC/DC CONVERTERS
Overview
The LM26480 provides the DC/DC converters that supply the various power needs of the application by means
of two linear low dropout regulators, LDO1 and LDO2, and two buck converters, SW1 and SW2. The table here
under lists the output characteristics of the various regulators.
Table 3. Supply Specification
Output
Supply Load
I
MAX
V
OUT
Range (V)
Maximum Output Current (mA)
LDO1 analog 1.0 to 3.5 300
LDO2 analog 1.0 to 3.5 300
SW1 digital 0.8 to 2.0 1500
SW2 digital 1.0 to 3.3 1500
Linear Low Dropout Regulators (LDOs)
LDO1 and LDO2 are identical linear regulators targeting analog loads characterized by low noise requirements.
LDO1 and LDO2 are enabled through the ENLDO pin.
No-Load Stability
The LDOs will remain stable and in regulation with no external load. This is an important consideration in some
circuits, for example, CMOS RAM keep-alive applications.
SW1, SW2: Synchronous Step-Down Magnetic DC/DC Converters
Functional Description
The LM26480 incorporates two high-efficiency synchronous switching buck regulators, SW1 and SW2, that
deliver a constant voltage from a single Li-Ion battery to the portable system processors. Using a voltage mode
architecture with synchronous rectification, both bucks have the ability to deliver up to 1500 mA depending on the
input voltage and output voltage (voltage head room), and the inductor chosen (maximum current capability).
There are three modes of operation depending on the current required - PWM, PFM, and shutdown. PWM mode
handles current loads of approximately 70 mA or higher, delivering voltage precision of +/-3% with 90% efficiency
or better. Lighter output current loads cause the device to automatically switch into PFM for reduced current
consumption (I
Q
= 33 µA typ.) and a longer battery life. The Standby operating mode turns off the device, offering
the lowest current consumption. PWM or PFM mode is selected automatically or PWM mode can be forced
through the setting of the buck control register.
Both SW1 and SW2 can operate up to a 100% duty cycle (PMOS switch always on) for low drop out control of
the output voltage. In this way the output voltage will be controlled down to the lowest possible input voltage.
Additional features include soft-start, under-voltage lock-out, current overload protection, and thermal overload
protection.
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