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LM3242 Datasheet(数据表) 11 Page - Texas Instruments

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部件型号  LM3242
说明  LM3242 6-MHz, 750-mA Miniature Adjustable Step-Down DC-DC Converter With Auto Bypass for RF Power Amplifiers
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制造商  TI [Texas Instruments]
网页  http://www.ti.com
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LM3242
www.ti.com
SNOSB48E – OCTOBER 2011 – REVISED AUGUST 2015
7 Detailed Description
7.1 Overview
The LM3242 is a simple, step-down DC-DC converter optimized for powering RF power amplifiers (PAs) in
mobile phones, portable communicators, and similar battery-powered RF devices. It is designed to allow the RF
PA to operate at maximum efficiency over a wide range of power levels from a single Li-Ion battery cell. It is
based on a voltage-mode buck architecture, with synchronous rectification for high efficiency. The device is
designed for a maximum load capability of 750 mA in PWM mode. Maximum load range may vary from this
depending on input voltage, output voltage, and the inductor chosen.
There are five modes of operation depending on the current required: PWM (Pulse Width Modulation), ECO
(ECOnomy), BP (Bypass), Sleep, and Shutdown. (See Table 1.) The LM3242 operates in PWM mode at higher
load current conditions. Lighter loads cause the device to automatically switch into ECO mode. Shutdown mode
turns the device off and reduces battery consumption to 0.1 µA (typical).
DC PWM mode output voltage precision is ±2% for 3.6 VOUT. Efficiency is typically around 95% (typical) for a
500-mA load with 3.3-V output, 3.9-V input. The output voltage is dynamically programmable from 0.4 V to 3.6 V
by adjusting the voltage on the control pin (VCON) without the need for external feedback resistors. This ensures
longer battery life by being able to change the PA supply voltage dynamically depending on its transmitting
power.
Additional features include current overload protection and thermal overload shutdown.
The LM3242 is constructed using a chip-scale 9-bump DSBGA package. This package offers the smallest
possible size, for space-critical applications such as cell phones, where board area is an important design
consideration. Use of a high switching frequency (6 MHz, typical) reduces the size of external components. As
shown in the Typical Application Circuit, only three external power components are required for implementation.
Use of a DSBGA package requires special design considerations for implementation. (See DSBGA Package
Assembly and Use.) Its fine bump-pitch requires careful board design and precision assembly equipment. Use of
this package is best suited for opaque-case applications, where its edges are not subject to high-intensity
ambient red or infrared light. Also, the system controller must set EN low during power-up and other low supply
voltage conditions. (See Shutdown Mode.)
Copyright © 2011–2015, Texas Instruments Incorporated
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