Datasheet LTM4668 (Analog Devices) - 7

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DECOUPLING REQUIREMENTS SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Switching Regulator Section: (Per Channel)
CIN External Input Capacitor Requirement IOUT = 1.2A 4.7 10 µF (VIN = 2.7V to 17V, VOUT = 1.5V) COUT External Output Capacitor Requirement IOUT = 1.2A 22 47 µF (VIN = 2.7V to 17V, VOUT = 1.5V)
OPERATION
The LTM4668 is a quad output standalone non-isolated Current mode control also provides cycle-by-cycle fast switch mode DC/DC power supply. It has built-in four overcurrent protection. An internal overvoltage and separate regulator channels and each of them can deliver undervoltage comparator pulls the open-drain PGOOD 1.2A continuous output current with few external input output low if the output feedback voltage exits a ±7.5% and output capacitors. Each regulator provides precisely window around the regulation point. Furthermore, in an regulated output voltage programmable via a single exter- overvoltage condition, internal top FET is turned off and nal resistor over 2.7V to 17V input voltage range. The bottom FET is turned on and held on until the overvoltage LTM4668 supports output voltages of 0.6V to 1.8V. The condition clears. typical application schematic is shown in Figure 17. Pulling the RUN pin below 0.35V forces the controller The LTM4668 uses a constant frequency, peak current into its shutdown state, turning off both power MOSFETs mode architecture and has integrated power MOSFETs, and most of the internal control circuitry. At light load inductors, and other supporting discrete components. The currents, pulse-skipping mode or Burst Mode operation typical switching frequency is set to 1MHz. For switching can be enabled to achieve higher efficiency compared to noise-sensitive applications, the µModule can be exter- continuous mode (CCM) by setting MODE/SYNC pin to nal y synchronized to a clock from 500kHz to 1.5MHz. See GND or INTVCC accordingly. The LTM4668 has internal the Applications Information section. 800µs soft-start ramp on each output channel. With current mode control and internal feedback loop The pin compatible µModule part LTM4668A is recom- compensation, the LTM4668 module has sufficient sta- mended when operating at a higher output voltage range bility margins and good transient performance with a wide of 0.6V to 5.5V and has a typical switching frequency range of output capacitors, even with all ceramic output of 2.25MHz. The differences between LTM4668 and capacitors. LTM4668A are shown in Table 1. Current mode control provides the flexibility of parallel-
Table 1.
ing any of the separate regulator channels with accurate
RECOMMENDED VOUT RANGE SWITCHING FREQUENCY
current sharing. With a built-in clock interleaving between LTM4668 0.6V to 1.8V 1MHz each two regulator channels, the LTM4668 could easily LTM4668A 0.6V to 5.5V 2.25MHz employ a 2+2, 3+1 or 4 channels parallel operation which is more than flexible in a multi-rail POL application. Rev. A For more information www.analog.com 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Electrical Characteristics Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Decoupling Requirements Operation Applications Information Package Description Revision History Package Photo Design Resources Related Parts