Datasheet LTM4637 (Analog Devices) - 9

LTM4637
Decoupling reQuireMenTs TA = 25°C. Use Figure 1 configuration. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
CIN External Input Capacitor Requirement IOUT = 20A, 4× 22µF Ceramic X7R Capacitors 88 µF (VIN = 4.5V to 20V, VOUT = 1.5V) (See Table 5) COUT External Output Capacitor Requirement IOUT = 20A (See Table 5) 400 µF (VIN = 4.5V to 20V, VOUT = 1.5V)
operaTion Power Module Description
Pulling the RUN pin below 1.1V forces the regulator into a The LTM4637 is a high performance single output stand- shutdown state. The TRACK/SS pin is used for program- alone nonisolated switching mode DC/DC power supply. ming the output voltage ramp and voltage tracking during It can provide a 20A output with few external input and start-up. See the Application Information section. output capacitors. This module provides precisely regu- The LTM4637 is internally compensated to be stable over lated output voltages programmable via external resistors all operating conditions. Table 5 provides a guideline for from 0.6VDC to 5.5VDC over a 4.5V to 20V input range. input and output capacitances for several operating condi- The typical application schematic is shown in Figure 22. tions. LTpowerCAD™ is available for transient and stability The LTM4637 has an integrated constant-frequency cur- analysis. The VFB pin is used to program the output voltage rent mode regulator, power MOSFETs, 0.6µH inductor, with a single external resistor to ground. and other supporting discrete components. The switching A remote sense amplifier is provided for accurately sensing frequency range is from 250kHz to 770kHz, and the typical output voltages ≤3.3V at the load point. operating frequency is shown in Table 5 for each VOUT. For Multiphase operation can be easily employed with the switching noise-sensitive applications, it can be externally synchronization inputs using an external clock source. synchronized from 250kHz to 800kHz, subject to minimum See application examples. on-time limitations. A single resistor is used to program the frequency. See the Applications Information section. High efficiency at light loads can be accomplished with selectable Burst Mode operation using the MODE_PLLIN With current mode control and internal feedback loop pin. These light load features will accommodate battery compensation, the LTM4637 module has sufficient stabil- operation. Efficiency graphs are provided for light load op- ity margins and good transient performance with a wide eration in the Typical Performance Characteristics section. range of output capacitors, even with all ceramic output capacitors. A TEMP pin is provided to allow the internal device tem- perature to be monitored using an onboard diode connected Current mode control provides cycle-by-cycle fast current PNP transistor. This diode connected PNP transistor is limit in an overcurrent condition. An internal overvoltage grounded in the module and can be used as a general monitor protects the output voltage in the event of an temperature monitor using a device that is designed to overvoltage >10%. The top MOSFET is turned off and the monitor the single-ended connection. bottom MOSFET is turned on until the output is cleared. Overtemperature protection will turn off the regulator’s RUN pin at ~130°C to 137°C. See Applications Information. 4637fc For more information www.linear.com/LTM4637 9 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 Typical Application Related Parts Design Resources