Datasheet LTM4645 (Analog Devices) - 10

LTM4645
operaTion Power Module Description
monitor protects the output voltage in the event of an The LTM4645 is a high performance single output stand- overvoltage >10%. The top MOSFET is turned off and the alone nonisolated switching mode DC/DC power supply. bottom MOSFET is turned on until the output is cleared. It can provide a 25A output with few external input and Pulling the RUN pin below 1.35V forces the regulator into output capacitors. This module provides precisely regu- a shutdown state. The TRACK/SS pin is used for pro- lated output voltages programmable via external resistors gramming the output voltage ramp and voltage tracking from 0.6V DC to 1.8V DC over a 4.7V to 15V input range. during start-up. See the Application Information section. The typical application schematic is shown in Figure 23 Multiphase operation can be easily employed by cascad- and Figure 24. ing the MODE/PLLIN input to the CLKOUT output. See the The LTM4645 has an integrated constant-frequency cur- Applications Information section and Figure 25 for example. rent mode regulator, power MOSFETs, inductor, and other For high reliability environment, N+1 phase redundancy supporting discrete components. The switching frequency can be easily implemented in LTM4645 together with a hot range is optimized from 400kHz to 900kHz, depending on swap controller, such as the LTC®4226, for extra system output voltage. For switching noise-sensitive applications, protection. By connecting the HIZB pin to the gate of the it can externally program to or be synchronized to a clock hot swap switch, any fault channel can be disconnected from 300kHz to 1MHz subject to minimum on-time and while the rest of the system is not affected. See Applica- inductor ripple current limitations. See the Applications tions Information section and Figure 27 for example. Information section. High efficiency at light loads can be accomplished with The LTM4645 is designed to use either external or internal phase shedding in multiphase operation or with selectable control loop compensation by shorting COMPb and COMPa pulse-skipping mode or Burst Mode operation in single pins together. With current mode control, the internal phase operation. Efficiency graphs are provided for light loop compensation has sufficient stability margins and load operation in the Typical Performance Characteristics good transient performance with a wide range of output section. capacitors, even with all ceramic output capacitors. Table 5 provides a guideline for input and output capacitances A remote sense amplifier is provided for accurately sensing for several different output conditions using the internal output voltages at the load point. loop compensation. The LTpowerCAD® design tool is A TEMP+ and TEMP– pins are provided to allow the internal available to download for optimizing the loop stability and device temperature to be monitored using an onboard transient response. diode connected PNP transistor. Current mode control provides cycle-by-cycle fast current limit in an overcurrent condition. An internal overvoltage 4645f 10 For more information www.linear.com/LTM4645 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Decoupling Requirements Operation Applications Information Typical Applications Package Description Package Photo Design Resources Related Parts