Datasheet LTM4644, LTM4644-1 (Analog Devices) - 9

LTM4644/LTM4644-1
DECOUPLING REQUIREMENTS (per Channel) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
CIN External Input Capacitor Requirement IOUT = 4A 4.7 10 µF (VIN = 4V to 14V, VOUT = 1.5V) COUT External Output Capacitor Requirement IOUT = 4A 22 47 µF (VIN = 4V to 14V, VOUT = 1.5V)
OPERATION
The LTM4644 is a quad output standalone non-isolated employ a 2+2, 3+1 or 4 channels parallel operation which switch mode DC/DC power supply. It has four separate is more than flexible in a multirail POL application like regulator channels with each of them capable of delivering FPGA. Furthermore, the LTM4644 has CLKIN and CLK- up to 4A continuous output current with few external input OUT pins for frequency synchronization or polyphasing and output capacitors. Each regulator provides precisely multiple devices which allow up to 8 phases cascaded to regulated output voltage programmable from 0.6V to 5.5V run simultaneously. via a single external resistor (two resistors for LTM4644-1) Current mode control also provides cycle-by-cycle fast over 4V to 14V input voltage range. With an external bias current monitoring. Foldback current limiting is provided voltage, this module can operate from an input voltage in an overcurrent condition to reduce the inductor valley as low as 2.375V. The typical application schematic is current to approximately 40% of the original value when shown in Figure 33. VFB drops. An internal overvoltage and undervoltage The LTM4644 integrates four separate constant frequency comparators pull the open-drain PGOOD output low if controlled on-time valley current mode regulators, power the output feedback voltage exits a ±10% window around MOSFETs, inductors, and other supporting discrete com- the regulation point. Continuous conduction mode (CCM) ponents. The typical switching frequency is set to 1MHz. operation is forced during OV and UV conditions except For switching noise-sensitive applications, the µModule during start-up when the TRACK pin is ramping up to 0.6V. regulator can be externally synchronized to a clock from Pulling the RUN pin below 1.1V forces the controller into 700kHz to 1.3MHz. See the Applications Information its shutdown state, turning off both power MOSFETs and section. most of the internal control circuitry. At light load cur- With current mode control and internal feedback loop rents, discontinuous conduction mode (DCM) operation compensation, the LTM4644 module has sufficient stabil- can be enabled to achieve higher efficiency compared to ity margins and good transient performance with a wide continuous conduction mode (CCM) by setting the MODE range of output capacitors, even with all ceramic output pin to SGND. The TRACK/SS pin is used for power supply capacitors. tracking and soft-start programming. See the Applications Current mode control provides the flexibility of paralleling Information section. any of the separate regulator channels with accurate cur- A temperature diode is included inside the module to moni- rent sharing. With a built-in clock interleaving between tor the temperature of the module. See the Applications each two regulator channels, the LTM4644 could easily Information section for details. Rev. G For more information www.analog.com 9 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Block Diagram Decoupling Requirements Operation Applications Information Typical Applications Package Description Revision History Package Photo Design Resources Related Parts