Datasheet LTM4650-1 (Analog Devices) - 10

link to page 29 LTM4650-1
operaTion Power Module Description
The LTM4650-1 is a dual-output standalone nonisolated The LTM4650-1 has a built-in 10pF high frequency filter switching mode DC/DC power supply with ±0.8% (A-Grade) cap from COMP to SGND for each output. An external RC total DC output error over line, load and temperature varia- filtering circuit is required to achieve fast Type II control tion. It can provide two 25A outputs with few external input loop compensation. Table 4 provides a guide line for input, and output capacitors and setup components. This module output capacitances and RC comp values for several oper- provides precisely regulated output voltages programmable ating conditions. The Linear Technology µModule Power via external resistors from 0.6VDC to 1.8VDC over 4.5V to Design Tool (LTpowerCAD®) will be provided for transient 15V input voltages. The typical application schematic is and stability analysis. The VFB pin is used to program the shown in Figure 24. output voltage with a single external resistor to ground. The LTM4650-1 has dual integrated constant-frequency A differential remote sense amplifier is available for sens- current mode regulators and built-in power MOSFET ing the output voltage accurately on one of the outputs at devices with fast switching speed. The typical switching the load point, or in parallel operation sensing the output frequency is from 400kHz to 600kHz depending on output voltage at the load point. voltage. For switching-noise sensitive applications, it can Multiphase operation can be easily employed with the be externally synchronized from 400kHz to 780kHz. A MODE_PLLIN, PHASMD, and CLKOUT pins. Up to resistor can be used to program a free run frequency on 12 phases can be cascaded to run simultaneously with the FSET pin. See the Applications Information section. respect to each other by programming the PHASMD pin to With current mode control, the LTM4650-1 module has different levels. See the Applications Information section. sufficient stability margins and good transient perfor- High efficiency at light loads can be accomplished with mance with a wide range of output capacitors, even with selectable Burst Mode operation or pulse-skipping opera- all ceramic output capacitors. tion using the MODE_PLLIN pin. These light load features Current mode control provides cycle-by-cycle fast current will accommodate battery operation. Efficiency graphs are limit and foldback current limit in an overcurrent condition. provided for light load operation in the Typical Performance Internal overvoltage and undervoltage comparators pull Characteristics section. See the Applications Information the open-drain PGOOD outputs low if the output feedback section for details. voltage exits a ±10% window around the regulation point. A general purpose temperature diode is included inside As the output voltage exceeds 10% above regulation, the the module to monitor the temperature of the module. See bottom MOSFET will turn on to clamp the output voltage. the Applications Information section for details. The top MOSFET will be turned off. This overvoltage protect The switch pins are available for functional operation is feedback voltage referred. monitoring and a resistor-capacitor snubber circuit can Pulling the RUN pins below 1.1V forces the regulators into be careful placed on the switch pin to ground to dampen a shutdown state, by turning off both MOSFETs. The TRACK any high frequency ringing on the transition edges. See pins are used for programming the output voltage ramp and the Applications Information section for details. voltage tracking during start-up or used for soft-starting the regulator. See the Applications Information section. 46501fc 10 For more information www.linear.com/LTM4650-1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Simplified Block Diagram Decoupling Requirements Operation Applications Information Typical Applications Package Description Revision History Package Photo Design Resources Related Parts