Datasheet LTM4623 (Analog Devices) - 9

LTM4623 OPERATION The LTM4623 is a standalone nonisolated switch mode DC/ comparators pull the open-drain PGOOD output low if the DC power supply. It can deliver up to 3A DC output current output feedback voltage exits a ±10% window around the with few external input and output capacitors. This module regulation point. Continuous operation is forced during OV provides precisely regulated output voltage adjustable and UV condition except during start-up when the TRACK between 0.6V to 5.5V via one external resistor over a 4V pin is ramping up to 0.6V. to 20V input voltage range. With an external bias supply Furthermore, in order to protect the internal power MOSFET above 4V connected to SVIN, this module operates with devices against transient voltage spikes, the LTM4623 an input voltage down to 2.375V. The typical application constantly monitors the V schematic is shown in Figure 24. IN pin for an overvoltage condi- tion. When VIN rises above 23.5V, the regulator suspends The LTM4623 contains an integrated constant on-time operation by shutting off both power MOSFETs. Once VIN valley current mode regulator, power MOSFETs, inductor, drops below 21.5V, the regulator immediately resumes and other supporting discrete components. The default normal operation. The regulator does not execute its switching frequency is 1MHz. For output voltages between soft-start function when exiting an overvoltage condition. 3.3V and 5.5V, an external 162k resistor is required between Multiphase operation can be easily employed with the FREQ and SGND pins to set the operating frequency to synchronization and phase mode controls. Up to 12 phases 2MHz to optimize inductor current ripple. For switching can be cascaded to run simultaneously with respect to noise-sensitive applications, the switching frequency can each other by programming the PHMODE pin to different be adjusted by external resistors and the μModule regulator levels. The LTM4623 has CLKIN and CLKOUT pins for can be externally synchronized to a clock within ±30% of PolyPhase operation of multiple devices or frequency the set frequency. See the Applications Information section. synchronization. With current mode control and internal feedback loop Pulling the RUN pin below 1.1V forces the controller into compensation, the LTM4623 module has sufficient stabil- its shutdown state, turning off both power MOSFETs ity margins and good transient performance with a wide and most of the internal control circuitry. At light load range of output capacitors, even with all ceramic output currents, discontinuous mode (DCM) operation can be capacitors. enabled to achieve higher efficiency compared to continu- Current mode control provides cycle-by-cycle fast cur- ous mode (CCM) by pulling the MODE pin to SGND. The rent limiting. Foldback current limiting is provided in an TRACK/SS pin is used for power supply tracking and overcurrent condition indicated by a drop in VFB reducing soft-start programming. See the Applications Informa- inductor valley current to approximately 40% of the origi- tion section. nal value. Internal output overvoltage and undervoltage Rev D For more information www.analog.com 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 Package Description Revision History Package Photos Design Resources Related Parts