LM3280 Datasheet, PDF (1/22 Pages) National Semiconductor (TI) – Adjustable Step-Down DC-DC Converter and 3 LDOs for RF Power Management

January 2007
LM3280
Adjustable Step-Down DC-DC Converter and 3 LDOs for RF
Power Management
General Description
The LM3280 is a multi-functional Power Management Unit,
optimized for low-power handheld applications such as Cel-
lular Phones.
The LM3280 incorporates three low-dropout LDO voltage
regulators and one step down PWM DC-DC converter with an
internal Bypass FET. The step down converter's output volt-
age can be set using an analog input (V_CON) for optimizing
efficiency of the RF PA at various power levels. The LDO op-
erates a nominal output voltage of 2.85V and maximum load
current capability of 20mA for a reference voltage required by
linear RF power amplifiers. The LM3280 additionally features
a separate enable pin for each output.
The LM3280 is available in a 16-pin lead free micro SMD
package.
Features
■ ^{2MHz (typ.) PWM Switching Frequency}
■ ^{Operates from a single Li-Ion cell (2.7V to 5.5V)}
■ ^{Adjustable Output Voltage (0.8V to 3.6V) DC-DC}
■ ^{High-efficiency synchronous buck converter}
■ ^{300mA Maximum load capability (PWM mode)}
■ ^{500mA Maximum load capability (Bypass mode)}
■ ^{PWM, Forced and Automatic Bypass Mode}
■ ^{3 Low-dropout and fast transient response LDOs}
■ ^{16-pin micro SMD Package}
■ ^{Current Overload Protection}
■ ^{Thermal Overload Protection}
Applications
■ ^{Cellular Phones}
■ ^{Hand-Held Radios}
■ ^{Battery Powered RF Devices}
Typical Application
FIGURE 1. LM3280 Typical Application
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