Datasheet LTM4648 (Analog Devices) - 9

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OPERATION Power Module Description
The LTM4648 is internally compensated to be stable over The LTM4648 is a high performance single output stand- all operating conditions. Table 3 provides a guideline alone nonisolated switching mode DC/DC power supply. for input and output capacitances for several operating It can provide up to 10A output current with few exter- conditions. The Analog Devices µModule Power Design nal input and output capacitors. This module provides Tool will be provided for transient and stability analysis. precisely regulated output voltage programmable via an The VFB pin is used to program the output voltage with a external resistor from 0.6VDC to 5VDC over a 2.375V to single external resistor to ground. 5.5V input range. The typical application schematic is A remote sense amplifier is provided in the LTM4648 for shown in Figure 18. accurately sensing output voltages ≤3.3V at the load point. The LTM4648 has an integrated constant-frequency cur- Multiphase operation can be easily employed with the rent mode regulator, power MOSFETs, inductor, and other synchronization inputs using an external clock source. supporting discrete components. The typical switching See application examples. frequency is 450kHz. For switching noise-sensitive ap- High efficiency at light loads can be accomplished with plications, it can be externally synchronized from 350kHz selectable Burst Mode operation using the MODE pin. These to 650kHz. See the Applications Information section. light load features will accommodate battery operation. With current mode control and internal feedback loop Efficiency graphs are provided for light load operation in compensation, the LTM4648 module has sufficient stabil- the Typical Performance Characteristics section. ity margins and good transient performance with a wide A diode connected PNP transistor with base and collector range of output capacitors, especially with all ceramic grounded is included in the module as a general purpose output capacitors. single-ended temperature monitor. The temperature Current mode control provides cycle-by-cycle fast current monitor is intended to be used as a general temperature limit in an overcurrent condition. An internal overvoltage monitor, see Applications Information section monitor protects the output voltage in the event of an The switching node pins are available for functional opera- overvoltage >10%. The top MOSFET is turned off and the tion monitoring and a resistor-capacitor snubber circuit bottom MOSFET is turned on until the output is cleared. can be careful placed on the switching node pin to ground Pulling the RUN pin below 1.1V forces the regulator into a to dampen any high frequency ringing on the transition shutdown state. The TRACK/SS pin is used for program- edges. See the Applications Information section for details. ming the output voltage ramp and voltage tracking during start-up. See the Applications Information section. Rev A For more information www.analog.com 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Typical Application Design Resources Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Design Resources Related Parts