Datasheet LTM4608A (Analog Devices) - 10

LTM4608A
OPERATION
With current mode control and internal feedback loop conditions. The Linear Technology µModule Power Design compensation, the LTM4608A module has sufficient Tool is provided for transient and stability analysis. The stability margins and good transient performance with FB pin is used to program the output voltage with a single a wide range of output capacitors, even with all ceramic external resistor to ground. output capacitors. Multiphase operation can be easily employed with the Current mode control provides cycle-by-cycle fast current synchronization and phase mode controls. Up to 12 phases limit and thermal shutdown in an overcurrent condition. can be cascaded to run simultaneously with respect to Internal overvoltage and undervoltage comparators pull each other by programming the PHMODE pin to different the open-drain PGOOD output low if the output feedback levels. The LTM4608A has clock in and clock out for poly voltage exits a ±10% window around the regulation point. phasing multiple devices or frequency synchronization. Pulling the RUN pin below 1.3V forces the controller into High efficiency at light loads can be accomplished with its shutdown state, by turning off both M1 and M2 at low selectable Burst Mode operation using the MODE pin. These load current. The TRACK pin is used for programming the light load features will accommodate battery operation. output voltage ramp and voltage tracking during start-up. Efficiency graphs are provided for light load operation in See Applications Information. the Typical Performance Characteristics. The LTM4608A is internally compensated to be stable Output voltage margining is supported, and can be pro- over all operating conditions. Table 3 provides a guideline gramed from ±5% to ±15% using the MGN and BSEL pins. for input and output capacitances for several operating The PGOOD pin is disabled during margining
APPLICATIONS INFORMATION
The typical LTM4608A application circuit is shown in no feedback resistor. Adding a resistor RFB from FB pin Figure 18. External component selection is primarily to GND programs the output voltage: determined by the maximum load current and output voltage. Refer to Table 3 for specific external capacitor VOUT = 0.596V • 10k +RFB requirements for a particular application. RFB
VIN to VOUT Step-Down Ratios Table 2. RFB Resistor vs Output Voltage
There are restrictions in the maximum V VOUT 0.596V 1.2V 1.5V 1.8V 2.5V 3.3V IN to VOUT step- down ratio that can be achieved for a given input voltage. RFB Open 10k 6.65k 4.87k 3.09k 2.21k The LTM4608A is 100% duty cycle, but the VIN to VOUT minimum dropout is a function of its load current. Please
Input Capacitors
refer to the curves in the Typical Performance Charac- The LTM4608A module should be connected to a low AC teristics section of this data sheet for more information. impedance DC source. Three 10µF ceramic capacitors are included inside the module. Additional input capaci-
Output Voltage Programming
tors are only needed if a large load step is required up to The PWM controller has an internal 0.596V reference the 4A level. A 47µF to 100µF surface mount aluminum voltage. As shown in the Block Diagram, a 10k 0.5% electrolytic bulk capacitor can be used for more input bulk internal feedback resistor connects V capacitance. This bulk input capacitor is only needed if OUT and FB pins together. The output voltage will default to 0.596V with the input source impedance is compromised by long in- ductive leads, traces or not enough source capacitance. 4608afe 10 For more information www.linear.com/LTM4608A Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Order Information Typical Performance Characteristics Pin Functions Simplified Block Diagram Operation Applications Information Typical Applications Package Description Package Photo Revision History Package Description Related Parts