Datasheet LTM4643 (Analog Devices) - 9

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DECOUPLING REQUIREMENTS (per Channel) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
CIN External Input Capacitor Requirement IOUT = 3A 4.7 10 µF (VIN = 4V to 20V, VOUT = 1.5V) COUT External Output Capacitor Requirement IOUT = 3A 22 47 µF (VIN = 4V to 20V, VOUT = 1.5V)
OPERATION
The LTM4643 is a quad output standalone non-isolated for 2+2, 3+1 or 4 channels parallel operation providing switch mode DC/DC power supply in 9mm  ×  15mm more design flexibility for multirail POL applications. Fur- × 1.82mm ultrathin package. It has four separate regula- thermore, the LTM4643 has CLKIN and CLKOUT pins for tor channels with each of them capable of delivering up frequency synchronization or polyphasing multiple devices to 3A continuous output current with few external input which allow up to 8 phases cascaded to run simultaneously. and output capacitors. Each regulator provides precisely Current mode control also provides cycle-by-cycle fast regulated output voltage programmable from 0.6V to current monitoring. Foldback current limiting is provided 3.3V via a single external resistor over 4V to 20V input in an overcurrent condition to reduce the inductor valley voltage range. With an external bias voltage, this module current to approximately 40% of the original value when can operate from an input voltage as low as 2.375V. The V typical application schematic is shown in Figure 29. FB drops. An internal overvoltage and undervoltage comparators pull the open-drain PGOOD output low if The LTM4643 integrates four separate constant frequency the output feedback voltage exits a ±10% window around controlled on-time valley current mode regulators, power the regulation point. Continuous conduction mode (CCM) MOSFETs, inductors, and other supporting discrete com- operation is forced during OV and UV conditions except ponents. The typical switching frequency is set to 1.2MHz. during start-up when the TRACK pin is ramping up to 0.6V. For switching noise-sensitive applications, the µModule Pulling the RUN pin below 1.1V forces the controller into regulator can be externally synchronized to a clock from its shutdown state, turning off both power MOSFETs and 850kHz to 1.5MHz. See the Applications Information most of the internal control circuitry. At light load cur- section. rents, discontinuous conduction mode (DCM) operation With current mode control and internal feedback loop can be enabled to achieve higher efficiency compared to compensation, the LTM4643 module has sufficient stabil- continuous conduction mode (CCM) by setting the MODE ity margins and good transient performance with a wide pin to SGND. The TRACK/SS pin is used for power supply range of output capacitors, even with all ceramic output tracking and soft-start programming. See the Applications capacitors. Information section. Current mode control provides the flexibility of paralleling A temperature diode is included inside the module to moni- any of the separate regulator channels with accurate cur- tor the temperature of the module. See the Applications rent sharing. With a built-in clock interleaving between Information section for details. regulator channels, the LTM4643 can easily be configured 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 Typical Applications Package Description Package Photo Related Parts