LTM4608 Low VIN, 8A DC/DC TM µModule with Tracking, Margining, and Frequency Synchronization FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION Complete Standalone Power Supply ±1.5% Output Voltage Regulation 2.375V to 5.5V Input Voltage Range 8A DC, 10A Peak Output Current 0.6V Up to 5V Output Output Voltage Tracking and Margining Power Good Tracks Margining Multiphase Operation Parallel Current Sharing Onboard Frequency Synchronization Spread Spectrum Frequency Modulation Overcurrent/Thermal Shutdown Protection Current Mode Control/Fast Transient Response Selectable Burst Mode® Operation Up to 95% Efficiency Output Overvoltage Protection Small Surface Mount Footprint, Low Profile (15mm × 9mm × 2.8mm) LGA Package APPLICATIONS ■ ■ ■ Telecom, Networking and Industrial Equipment Storage Systems Point of Load Regulation The LTM®4608 is a complete 8A switch mode DC/DC power supply. Included in the package are the switching controller, power FETs, inductor and all support components. Operating over an input voltage range of 2.375V to 5.5V, the LTM4608 supports an output voltage range of 0.6V to 5V, set by a single external resistor. This high efficiency design delivers up to 8A continuous current (10A peak). Only bulk input and output capacitors are needed. The low profile package (2.8mm) enables utilization of unused space on the back side of PC boards for high density point-of-load regulation. The high switching frequency and a current mode architecture enable a very fast transient response to line and load changes without sacrificing stability. The device supports frequency synchronization, programmable multiphase and/or spread spectrum operation, output voltage tracking for supply rail sequencing and voltage margining. Fault protection features include overvoltage protection, overcurrent protection and thermal shutdown. The power module is offered in a compact and thermally enhanced 15mm × 9mm × 2.8mm LGA package. The LTM4608 is Pb-free and RoHS compliant . , LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. μModule is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Efficiency vs Load Current 100 3V to 5.5V Input to 1.8V Output DC/DC μModule 95 CLKIN VIN CLKIN VOUT SVIN FB ITH SW RUN VOUT 1.8V 100μF LTM4608 4.87k ITHM PLLLPF PGOOD TRACK MGN CLKOUT GND SGND EFFICIENCY (%) VIN = 3.3V VIN 3V TO 5.5V 10μF 90 VIN = 5V 85 80 PGOOD VOUT 4608 TA01a 75 VOUT = 1.8V 70 0 2 4 6 LOAD CURRENT (A) 8 10 4608 TA01b 4608f 1 LTM4608 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VIN, SVIN ...................................................... –0.3V to 6V CLKOUT ....................................................... –0.3V to 2V PGOOD, PLLLPF, CLKIN, PHMODE, MODE...–0.3V to VIN ITH, ITHM, RUN, FB, TRACK,MGN, BSEL .......–0.3V to VIN VOUT, VSW .......................................–0.3V to (VIN + 0.3V) Operating Temperature Range (Note 2).... –40°C to 85°C Junction Temperature ........................................... 125°C Storage Temperature Range................... –55°C to 125°C TOP VIEW A B GND C D E F G CNTRL GND VIN 1 2 SW 3 4 5 6 CNTRL 7 8 9 10 11 GND VOUT LGA PACKAGE 68-PIN (15mm × 9mm × 2.8mm) TJMAX = 125°C, θJA = 25°C/W, θJP = 7°C/W, θJC = 50°C/W, WEIGHT = 1.0g ORDER INFORMATION LEAD FREE FINISH PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE (NOTE 2) LTM4608EV#PBF LTM4608V 68-Lead (15mm × 9mm × 2.8mm) LGA –40°C to 85°C LTM4608IV#PBF LTM4608V 68-Lead (15mm × 9mm × 2.8mm) LGA –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ This product is only offered in trays. For more information go to: http://www.linear.com/packaging/ ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 5V unless otherwise noted. See Figure 18. SYMBOL PARAMETER VIN(DC) Input DC Voltage VOUT(DC) Output Voltage CONDITIONS CIN = 10μF × 1, COUT = 100μF Ceramic, 100μF POSCAP, RFB = 6.65k VIN = 2.375V to 5.5V, VOUT = 1.5V, IOUT = 0A MIN ● 2.375 ● 1.475 1.468 2.05 1.85 TYP MAX UNITS 5.5 V 1.49 1.49 1.505 1.512 V V 2.2 2.0 2.35 2.15 V V Input Specifications VIN(UVLO) Undervoltage Lockout Threshold SVIN Rising SVIN Falling 4608f 2 LTM4608 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 5V unless otherwise noted. See Figure 18. SYMBOL PARAMETER CONDITIONS MIN IQ(VIN) Input Supply Bias Current VIN = 3.3V, VOUT = 1.5V, No Switching, Mode = VIN VIN = 3.3V, VOUT = 1.5V, No Switching, Mode = 0V VIN = 3.3V, VOUT = 1.5V, Switching Continuous 400 1.15 55 μA mA mA VIN = 5V, VOUT = 1.5V, No Switching, Mode = VIN VIN = 5V, VOUT = 1.5V, No Switching, Mode = 0V VIN = 5V, VOUT = 1.5V, Switching Continuous 450 1.3 75 μA mA mA 1 μA 3.75 4.5 2.93 A A A Shutdown, RUN = 0, VIN = 5V IS(VIN) Input Supply Current VIN = 2.375V, VOUT = 1.5V, IOUT = 5A VIN = 3.3V, VOUT = 1.5V, IOUT = 8A VIN = 5V, VOUT = 1.5V, IOUT = 8A TYP MAX UNITS Output Specifications IOUT(DC) ΔVOUT(LINE) Output Continuous Current Range VOUT = 1.5V (See Output Current Derating VIN = 3.3V, 5.5V Curves for Different VIN, VOUT VIN = 2.375V and TA) 0 0 8 5 A A Line Regulation Accuracy VOUT = 1.5V, VIN from 2.375V to 5.5V, IOUT = 0A ● 0.1 0.2 %/V Load Regulation Accuracy VOUT = 1.5V VIN = 3.3V, 5.5V, ILOAD = 0A to 8A VIN = 2.375V, ILOAD = 0A to 5A ● ● 0.3 0.3 0.75 0.75 % % VOUT ΔVOUT(LOAD) VOUT VOUT(AC) Output Ripple Voltage IOUT = 0A, COUT = 100μF/X5R/Ceramic, VIN = 5V, VOUT = 1.5V fS Switching Frequency IOUT = 8A, VIN = 5V, VOUT = 1.5V fSYNC SYNC Capture Range ΔVOUT(START) Turn-On Overshoot tSTART Turn-On Time 10 1.3 1.5 0.75 mVP-P 1.7 MHz 2.25 MHz COUT = 100μF, VOUT = 1.5V, IOUT = 0A VIN = 3.3V VIN = 5V 10 10 mV mV COUT = 100μF, VOUT = 1.5V, IOUT = 1A, Resistive Load, Track = VIN, VIN = 5V 100 μs ΔVOUT(LS) Peak Deviation for Dynamic Load Load: 0% to 50% to 0% of Full Load, COUT = 100μF Ceramic, 100μF POSCAP, VIN = 5V, VOUT = 1.5V 15 mV tSETTLE Settling Time for Dynamic Load Step Load: 0% to 50% to 0% of Full Load, VIN = 5V, VOUT = 1.5V, COUT = 100μF 10 μs IOUT(PK) Output Current Limit COUT = 100μF VIN = 2.375V, VOUT = 1.5V VIN = 3.3V, VOUT = 1.5V VIN = 5V, VOUT = 1.5V 8 11 13 A A A Control Section VFB Voltage at FB Pin SS Delay Internal Soft-Start Delay IOUT = 0A, VOUT = 1.5V, VIN = 2.375V to 5.5V ● 0.592 0.589 IFB VRUN RUN Pin On/Off Threshold RUN Rising RUN Falling 1.4 1.3 0.596 0.596 0.600 0.603 V V 90 μs 0.2 μA 1.55 1.4 1.7 1.5 V V 4608f 3 LTM4608 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 5V unless otherwise noted. See Figure 18. SYMBOL PARAMETER CONDITIONS TRACK Tracking Threshold (Rising) Tracking Threshold (Falling) Tracking Disable Threshold RUN = VIN RUN = 0V RFBHI Resistor Between VOUT and FB Pins ΔVPGOOD PGOOD Range %Margining Output Voltage Margining Percentage MIN TYP MAX 0.57 0.18 VIN – 0.5 9.95 10 V V V 10.05 ±10 MGN = VIN, BSEL = 0V MGN = VIN, BSEL = VIN MGN = VIN, BSEL = Float MGN = 0V, BSEL = 0V MGN = 0V, BSEL = VIN MGN = 0V, BSEL = Float Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. 4 9 14 –4 –9 –14 5 10 15 –5 –10 –15 UNITS kΩ % 6 11 16 –6 –11 –16 % % % % % % Note 2: The LTM4608E is guaranteed to meet performance specifications from 0°C to 85°C. Specifications over the – 40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTM4608I is guaranteed and tested over the –40°C to 85°C temperature range. 4608f 4 LTM4608 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current Efficiency vs Load Current 100 CONTINUOUS MODE Efficiency vs Load Current 100 CONTINUOUS MODE 95 95 90 90 90 85 80 5VIN 1.2VOUT 5VIN 1.5VOUT 5VIN 1.8VOUT 5VIN 2.5VOUT 5VIN 3.3VOUT 75 70 0 2 4 LOAD CURRENT EFFICIENCY (%) 95 EFFICIENCY (%) EFFICIENCY (%) 100 per Figure 18 Typcial Application 85 80 3.3VIN 1.2VOUT 3.3VIN 1.5VOUT 3.3VIN 1.8VOUT 3.3VIN 2.5VOUT 75 0 8 2 6 0 8 4.0 3.0 80 VOUT (V) 2.5 VOUT = 1.5V VOUT = 2.5V VOUT = 3.3V 40 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 LOAD CURRENT (A) 3.0 2.5 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 0 0 1 2 3 VIN (V) IOUT = 5A VOUT = 1.2V VOUT = 1.5V VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V 3.5 VOUT (V) 90 4 4608 G04 0 5 6 0 1 2 3 VIN (V) 4 5 6 4608 G06 4608 G05 Supply Current vs VIN 7 6 VIN to VOUT Step-Down Ratio 4.0 IOUT = 8A VOUT = 1.2V VOUT = 1.5V VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V 3.5 60 4 3 2 5 LOAD CURRENT (A) 1 4608 G03 VIN to VOUT Step-Down Ratio 100 70 2.5VIN 1.0VOUT 2.5VIN 1.5VOUT 2.5VIN 1.8VOUT 4608 G02 Burst Mode Efficiency with 5V Input EFFICIENCY (%) 80 70 4 LOAD CURRENT 4608 G01 50 85 75 70 6 CONTINUOUS MODE Load Transient Response Load Transient Response 1.6 SUPPLY CURRENT (mA) 1.4 1A/DIV 1.2 VO = 1.2V PULSE-SKIPPING MODE 2A/DIV 1 20mV/DIV 0.8 0.6 20mV/DIV VO = 1.2V BURST MODE 0.4 0.2 0 2.5 3 3.5 4 4.5 INPUT VOLTAGE (V) 5 5.5 VIN = 5V 20μs/DIV VOUT = 3.3V 2A/μs STEP COUT = 100μF X5R C1 = 100pF, C3 = 22pF FROM FIGURE 18 4608 G08 VIN = 5V 20μs/DIV VOUT = 2.5V 2.5A/μs STEP COUT = 100μF X5R C1 = 120pF, C3 = 47pF FROM FIGURE 18 4608 G09 4608 G07 4608f 5 LTM4608 TYPICAL PERFORMANCE CHARACTERISTICS per Figure 18 Typcial Application Load Transient Response Load Transient Response Load Transient Response 2A/DIV 2A/DIV 2A/DIV 20mV/DIV 20mV/DIV 20mV/DIV 4608 G10 VIN = 5V 20μs/DIV VOUT = 1.8V 2.5A/μs STEP COUT = 100μF X5R C1 = NONE, C3 = NONE FROM FIGURE 18 4608 G11 VIN = 5V 20μs/DIV VOUT = 1.5V 2.5A/μs STEP COUT = 100μF X5R C1 = NONE, C3 = NONE FROM FIGURE 18 4608 G12 VIN = 5V 20μs/DIV VOUT = 1.2V 2.5A/μs STEP COUT = 2 × 100μF C1 = 100pF, C3 = NONE FROM FIGURE 18 VFB vs Temperature Start-Up Load Regulation vs Current 0.5 602 FC MODE VIN = 3.3V VOUT = 1.8V 0.4 600 VOUT 0.5V/DIV 0.3 VFB (mV) 598 VIN 2V/DIV LOAD REGULATION (%) VIN = 5.5V VIN = 3.3V 596 VIN = 2.375V 594 VIN = 5V 50μs/DIV VOUT = 1.5V COUT = 100μF NO LOAD AND 8A LOAD (DEFAULT 100μs SOFT-START) 4608 G13 0.2 0.1 0 –0.1 –0.2 –0.3 592 –0.4 590 –50 –25 0 50 25 TEMPERATURE (°C) 75 100 –0.5 0 1 2 4608 G14 3 6 4 5 LOAD CURRENT (A) 7 8 4608 G15 Short-Circuit Protection (2.5V Short, No Load) 2.5V Output Current Short-Circuit Protection (2.5V Short, 4A Load) 3.0 2V/DIV 2.5 VIN 5V/DIV VIN OUTPUT VOLTAGE (V) 5V/DIV 2V/DIV 2.0 VOUT VOUT IOUT LOAD 5A/DIV 5A/DIV 1.5 IOUT IOUT SHORT 5A/DIV 1.0 VIN = 5V VOUT = 2.5V 0.5 50μs/DIV 4608 G17 VIN = 5V VOUT = 2.5V 50μs/DIV 4608 G18 0 0 5 10 15 OUTPUT CURRENT (A) 20 4608 G16 4608f 6 LTM4608 PIN FUNCTIONS VIN (C1, C8, C9, D1, D3-D5, D7-D9 and E8): Power Input Pins. Apply input voltage between these pins and GND pins. Recommend placing input decoupling capacitance directly between VIN pins and GND pins. VOUT (C10-C11, D10-D11, E9-E11, F9-F11, G9-G11): Power Output Pins. Apply output load between these pins and GND pins. Recommend placing output decoupling capacitance directly between these pins and GND pins. See Table 1. GND (A1-A11, B1, B9-B11, F3, F7-F8, G1-G8): Power Ground Pins for Both Input and Output Returns. SVIN (F4): Signal Input Voltage. This pin is internally connected to VIN through a lowpass filter. SGND (E1): Signal Ground Pin. Return ground path for all analog and low power circuitry. Tie a single connection to GND in the application. MODE (B5): Mode Select Input. Tying this pin high enables Burst Mode operation. Tying this pin low enables forced continuous operation. Floating this pin or tying it to VIN/2 enables pulse-skipping operation. CLKIN (B3): External Synchronization Input to Phase Detector. This pin is internally terminated to SGND with a 50k resistor. The phase locked loop will force the internal top power PMOS turn on to be synchronized with the rising edge of the CLKIN signal. Connect this pin to SVIN to enable spread spectrum modulation. During external synchronization, make sure the PLLLPF pin is not tied to VIN or GND. PLLLPF (E3): Phase Locked Loop Lowpass Filter. An internal lowpass filter is tied to this pin. In spread spectrum mode, placing a capacitor here to SGND controls the slew rate from one frequency to the next. Alternatively, floating this pin allows normal running frequency at 1.5MHz, tying this pin to SVIN forces the part to run at 1.33 times its normal frequency (2MHz), tying it to ground forces the frequency to run at 0.67 times its normal frequency (1MHz). PHMODE (B4): Phase Selector Input. This pin determines the phase relationship between the internal oscillator and CLKOUT. Tie it high for 2-phase operation, tie it low for 3-phase operation, and float or tie it to VIN/2 for 4-phase operation. MGN (B8): Margining Pin. Tie this pin to VOUT to disable margining. For margining, connect a voltage divider from VIN to GND with the center point connected to the MGN pin. Each resistor ≈ 50k. See Applications Information and Figure 18. BSEL (B7): Margining Bit Select Pin. Tying BSEL low selects ±5%, tying it high selects ±10%. Floating it or tying it to VIN/2 selects ±15%. TRACK (E5): Output Voltage Tracking Pin. Voltage tracking is enabled when the TRACK voltage is below 0.57V. If tracking is not desired, then connect the TRACK pin to SVIN. If TRACK is not tied to SVIN, then the TRACK pin’s voltage needs to be below 0.18V before the chip shuts down even though RUN is already low. Do not float this pin. A resistor divider and capacitor can be applied to the TRACK pin to increase the soft-start time of the regulator. See Applications Information. Can tie together for parallel operation and tracking. Load current needs to be present during track down. FB (E7): The Negative Input of the Error Amplifier. Internally, this pin is connected to VOUT with a 10k precision resistor. Different output voltages can be programmed with an additional resistor between FB and GND pins. In PolyPhase® operation, tie FB pins together for parallel operation. See Applications Information for details. ITH (F6): Current Control Threshold and Error Amplifier Compensation Point. The current comparator threshold increases with this control voltage. Tie together in parallel operation. ITHM (F5): Negative Input to the Internal ITH Differential Amplifier. Tie this pin to SGND for single phase operation. For PolyPhase operation, tie the master’s ITHM to SGND while connecting all of the ITHM pins together. PolyPhase is a registered trademark of Linear Technology Corporation. 4608f 7 LTM4608 PIN FUNCTIONS SW (C3-C5): Switching Node of the Circuit is Used for Testing Purposes. This can be connected to copper on the board for improved thermal performance. PGOOD (C7): Output Voltage Power Good Indicator. Open-drain logic output that is pulled to ground when the output voltage is not within ±10% of the regulation point. Disabled during margining. CLKOUT (F2): Output Clock Signal for PolyPhase Operation. The phase of CLKOUT is determined by the state of the PHMODE pin. RUN (F1): Run Control Pin. A voltage above 1.5V will turn on the module. TOP VIEW A B GND C D VIN E F G CNTRL GND 1 2 SW 3 4 5 6 CNTRL 7 8 9 10 11 GND VOUT LGA PACKAGE 68-PIN (15mm × 9mm × 2.8mm) 4608f 8 LTM4608 SIMPLIFIED BLOCK DIAGRAM SVIN VIN INTERNAL FILTER TRACK 10μF 10μF VIN 2.375 TO 5.5V + 10μF CIN MGN BSEL SW M1 PGOOD MODE L POWER CONTROL RUN VOUT 1.5V 8A VOUT CLKIN CLKOUT M2 22pF 22μF COUT PHMODE GND ITH 10k INTERNAL COMP PLLLPF FB RFB 6.65k INTERNAL FILTER ITHM SGND 4608 BD Figure 1. Simplified LTM4608 Block Diagram Table 1. Decoupling Requirements. TA = 25°C, Block Diagram Configuration. SYMBOL PARAMETER CONDITIONS CIN External Input Capacitor Requirement (VIN = 2.375V to 5.5V, VOUT = 1.5V) IOUT = 8A COUT External Output Capacitor Requirement (VIN = 2.375V to 5.5V, VOUT = 1.5V) IOUT = 8A MIN TYP 10 MAX UNITS μF 100 μF OPERATION The LTM4608 is a standalone nonisolated switch mode DC/DC power supply. It can deliver up to 8A of DC output current with few external input and output capacitors. This module provides precisely regulated output voltage programmable via one external resistor from 0.6V DC to 5.0V DC over a 2.375V to 5.5V input voltage. The typical application schematic is shown in Figure 18. The LTM4608 has an integrated constant frequency current mode regulator and built-in power MOSFET devices with fast switching speed. The typical switching frequency is 1.5MHz. For switching noise sensitive applications, it can be externally synchronized from 0.75MHz to 2.25MHz. Even spread spectrum switching can be implemented in the design to reduce noise. With current mode control and internal feedback loop compensation, the LTM4608 module has sufficient stability margins and good transient performance with a wide range of output capacitors, even with all ceramic output capacitors. 4608f 9 LTM4608 OPERATION Current mode control provides cycle-by-cycle fast current limit and thermal shutdown in an overcurrent condition. Internal overvoltage and undervoltage comparators pull the open-drain PGOOD output low if the output feedback voltage exits a ±10% window around the regulation point. Pulling the RUN pin below 1.3V forces the controller into its shutdown state, by turning off both M1 and M2 at low load current. The TRACK pin is used for programming the output voltage ramp and voltage tracking during start-up. See Applications Information. The LTM4608 is internally compensated to be stable over all operating conditions. Table 3 provides a guideline for input and output capacitances for several operating conditions. The Linear Technology μModule Power Design Tool is provided for transient and stability analysis. The FB pin is used to program the output voltage with a single external resistor to ground. Multiphase operation can be easily employed with the synchronization and phase mode controls. Up to 12 phases can be cascaded to run simultaneously with respect to each other by programming the PHMODE pin to different levels. The LTM4608 has clock in and clock out for poly phasing multiple devices or frequency synchronization. High efficiency at light loads can be accomplished with selectable Burst Mode operation using the MODE pin. These light load features will accommodate battery operation. Efficiency graphs are provided for light load operation in the Typial Performance Characteristics. Output voltage margining is supported, and can be programed from ±5% to ±15% using the MGN and BSEL pins. The PGOOD pin is disabled during margining APPLICATIONS INFORMATION The typical LTM4608 application circuit is shown in Figure 18. External component selection is primarily determined by the maximum load current and output voltage. Refer to Table 3 for specific external capacitor requirements for a particular application. VIN to VOUT Step-Down Ratios There are restrictions in the maximum VIN to VOUT stepdown ratio that can be achieved for a given input voltage. The LTM4608 is 100% duty cycle, but the VIN to VOUT minimum drop out is still shown as a function of its load current. For 5V input, all outputs can deliver 8A. For 3.3V input, all outputs can deliver 8A, except 2.5V which is limited to 6A. Output Voltage Programming The PWM controller has an internal 0.596V reference voltage. As shown in the Block Diagram, a 10kΩ/0.5% internal feedback resistor connects VOUT and FB pins together. The output voltage will default to 0.596V with no feedback resistor. Adding a resistor RFB from FB pin to GND programs the output voltage: VOUT = 0.596 V • 10k + RFB RFB Table 2. RFB Resistor vs Output Voltage VOUT 0.596V 1.2V 1.5V 1.8V 2.5V 3.3V RFB Open 10k 6.65k 4.87k 3.09k 2.21k Input Capacitors The LTM4608 module should be connected to a low AC impedance DC source. Three 10μF ceramic capacitors are included inside the module. Additional input capacitors are only needed if a large load step is required up to the 4A level. A 47μF to 100μF surface mount aluminum electrolytic bulk capacitor can be used for more input bulk capacitance. This bulk input capacitor is only needed if the input source impedance is compromised by long inductive leads, traces or not enough source capacitance. If low impedance power planes are used, then this 47μF capacitor is not needed. For a buck converter, the switching duty-cycle can be estimated as: 4608f 10 LTM4608 APPLICATIONS INFORMATION D= Burst Mode Operation VOUT VIN Without considering the inductor current ripple, the RMS current of the input capacitor can be estimated as: ICIN(RMS) = IOUT(MAX) η% • D • (1– D) In the above equation, η% is the estimated efficiency of the power module. The bulk capacitor can be a switcherrated electrolytic aluminum capacitor, polymer capacitor for bulk input capacitance due to high inductance traces or leads. If a low inductance plane is used to power the device, then only one 10μF ceramic is required. The three internal 10μF ceramics are typically rated for 2A of RMS ripple current, so the ripple current at the worse case for 8A maximum current is 4A or less. Output Capacitors The LTM4608 is designed for low output voltage ripple noise. The bulk output capacitors defined as COUT are chosen with low enough effective series resistance (ESR) to meet the output voltage ripple and transient requirements. COUT can be a low ESR tantalum capacitor, a low ESR polymer capacitor or ceramic capacitor. The typical output capacitance range is from 47μF to 220μF. Additional output filtering may be required by the system designer, if further reduction of output ripple or dynamic transient spikes is required. Table 3 shows a matrix of different output voltages and output capacitors to minimize the voltage droop and overshoot during a 3A/μs transient. The table optimizes total equivalent ESR and total bulk capacitance to optimize the transient performance. Stability criteria are considered in the Table 3 matrix, and the Linear Technology μModule Power Design Tool will be provided for stability analysis. Multiphase operation will reduce effective output ripple as a function of the number of phases. Application Note 77 discusses this noise reduction versus output ripple current cancellation, but the output capacitance will be more a function of stability and transient response. The Linear Technology μModule Power Design Tool will calculate the output ripple reduction as the number phases implemented increases by N times. The LTM4608 is capable of Burst Mode operation in which the power MOSFETs operate intermittently based on load demand, thus saving quiescent current. For applications where maximizing the efficiency at very light loads is a high priority, Burst Mode operation should be applied. To enable Burst Mode operation, simply tie the MODE pin to VIN. During this operation, the peak current of the inductor is set to approximately 20% of the maximum peak current value in normal operation even though the voltage at the ITH pin indicates a lower value. The voltage at the ITH pin drops when the inductor’s average current is greater than the load requirement. As the ITH voltage drops below 0.2V, the BURST comparator trips, causing the internal sleep line to go high and turn off both power MOSFETs. In sleep mode, the internal circuitry is partially turned off, reducing the quiescent current to about 450μA. The load current is now being supplied from the output capacitor. When the output voltage drops, causing ITH to rise above 0.25V, the internal sleep line goes low, and the LTM4608 resumes normal operation. The next oscillator cycle will turn on the top power MOSFET and the switching cycle repeats. Pulse-Skipping Mode Operation In applications where low output ripple and high efficiency at intermediate currents are desired, pulse-skipping mode should be used. Pulse-skipping operation allows the LTM4608 to skip cycles at low output loads, thus increasing efficiency by reducing switching loss. Floating the MODE pin or tying it to VIN/2 enables pulse-skipping operation. This allows discontinuous conduction mode (DCM) operation down to near the limit defined by the chip’s minimum on-time (about 100ns). Below this output current level, the converter will begin to skip cycles in order to maintain output regulation. Increasing the output load current slightly, above the minimum required for discontinuous conduction mode, allows constant frequency PWM. Forced Continuous Operation In applications where fixed frequency operation is more critical than low current efficiency, and where the lowest output ripple is desired, forced continuous operation should be used. Forced continuous operation can be enabled by 4608f 11 LTM4608 APPLICATIONS INFORMATION Table 3. Output Voltage Response Versus Component Matrix (Refer to Figure 18) 0A to 3A Load Step TYPICAL MEASURED VALUES VALUE COUT1 VENDORS TDK 22μF, 6.3V Murata 22μF TDK 100μF, 6.3V Murata 100μF, 6.3V VOUT (V) 1.0 1.0 1.0 1.0 1.0 1.0 1.2 1.2 1.2 1.2 1.2 1.2 1.5 1.5 1.5 1.5 1.5 1.5 1.8 1.8 CIN (CERAMIC) 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF 10μF CIN (BULK)* 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF 100μF PART NUMBER C3216X7S0J226M GRM31CR61C226KE15L C4532X5R0J107MZ GRM32ER60J107M COUT1 (CERAMIC) 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 2 22μF × 1 100μF × 1 22μF × 1 COUT2 (BULK) COUT2 VENDORS Sanyo POSCAP CIN (BULK) VENDORS Sanyo VALUE 150μF, 10V VALUE 100μF, 10V PART NUMBER 10TPD150M PART NUMBER 10CE100FH ITH None None None None None None None None None None None None None None None None None None None None C1 68pF None 68pF None 68pF None 100pF None 100pF None 100pF 47pF 100pF None 100pF None 100pF None 47pF None C3 None 100pF None 100pF None 100pF None 100pF None 100pF None None None 47pF None 47pF None None None 47pF VIN (V) 5 5 3.3 3.3 2.5 2.5 5 5 3.3 3.3 2.5 2.5 5 5 3.3 3.3 2.5 2.5 5 5 DROOP (mV) 13 17 13 17 13 17 16 20 16 20 16 16 18 20 16 20 18 20 22 21 PEAK-TO- PEAK DEVIATION (mV) 26 34 26 34 26 34 32 41 32 41 32 32 36 41 32 41 36 41 42 42 RECOVERY TIME (μs) 7 8 7 10 7 8 8 10 8 10 10 8 8 12 10 12 10 12 8 12 LOAD STEP (A/μs) 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 RFB (kΩ) 14.7 14.7 14.7 14.7 14.7 14.7 10 10 10 10 10 10 6.65 6.65 6.65 6.65 6.65 6.65 4.87 4.87 1.8 10μF 100μF 100μF × 2 None 1.8 10μF 100μF 22μF × 1 150μF × 2 None 1.8 10μF 100μF 100μF × 2 None 1.8 10μF 100μF 22μF × 1 150μF × 2 None 2.5 10μF 100μF 100μF × 1 None 2.5 10μF 100μF 22μF × 1 150μF × 1 None 2.5 10μF 100μF 100μF × 1 None 2.5 10μF 100μF 22μF × 1 150μF × 1 None 3.3 10μF 100μF 100μF × 1 100pF 3.3 10μF 100μF 22μF × 1 150μF × 1 None *Bulk capacitance is optional if VIN has very low input impedance. 120pF None 120pF None 100pF 22pF 100pF 22pF 22pF None None 47pF None None None None None None None None 3.3 3.3 2.5 2.5 5 5 3.3 3.3 5 5 21 21 22 21 28 33 30 21 38 39 43 41 44 42 42 60 60 41 74 75 12 12 12 14 10 10 10 10 10 12 3 3 3 3 3 3 3 3 3 3 4.87 4.87 4.87 4.87 3.09 3.09 3.09 3.09 3.09 3.09 150μF × 2 150μF × 2 150μF × 2 150μF × 2 150μF × 2 150μF × 2 150μF × 2 150μF × 2 150μF × 2 150μF × 2 tying the MODE pin to GND. In this mode, inductor current is allowed to reverse during low output loads, the ITH voltage is in control of the current comparator threshold throughout, and the top MOSFET always turns on with each oscillator pulse. During start-up, forced continuous mode is disabled and inductor current is prevented from reversing until the LTM4608’s output voltage is in regulation. Multiphase Operation For output loads that demand more than 8A of current, multiple LTM4608s can be cascaded to run out of phase to provide more output current without increasing input and output voltage ripples. The CLKIN pin allows the LTC4608 to synchronize to an external clock (between 0.75MHz and 2.25MHz) and the internal phase locked 4608f 12 LTM4608 APPLICATIONS INFORMATION loop allows the LTM4608 to lock onto CLKIN’s phase as well. The CLKOUT signal can be connected to the CLKIN pin of the following LTM4608 stage to line up both the frequency and the phase of the entire system. Tying the PHMODE pin to SVIN, SGND or SVIN/2 (floating) generates a phase difference (between CLKIN and CLKOUT) of 180°, 120° or 90° respectively, which corresponds to a 2-phase, 3-phase or 4-phase operation. A total of 12 phases can be cascaded to run simultaneously with respect to each other by programming the PHMODE pin of each LTM4608 to different levels. For a 6-phase example in Figure 2, the 2nd stage that is 120° out of phase from the 1st stage can generate a 240° (PHMODE = 0) CLKOUT signal for the 3rd stage, which then can generate a CLKOUT signal that’s 420°, or 60° (PHMODE = SVIN) for the 4th stage. With the 60° CLKIN input, the next two stages can shift 120° (PHMODE = 0) for each to generate a 300° signal for the 6th stage. Finally, the signal with a 60° phase shift on 0 120 CLKIN CLKOUT +120 PHMODE PHASE 1 A multiphase power supply significantly reduces the amount of ripple current in both the input and output capacitors. The RMS input ripple current is reduced by, and the effective ripple frequency is multiplied by, the number of phases used (assuming that the input voltage is greater than the number of phases used times the output voltage). The output ripple amplitude is also reduced by the number of phases used. The LTM4608 device is an inherently current mode controlled device. Parallel modules will have very good current sharing. This will balance the thermals on the design. Tie the ITH pins of each LTM4608 together to share the current evenly. To reduce ground potential noise, tie the ITHM pins of all LTM4608s together and then connect to (420) 60 240 CLKIN CLKOUT PHMODE the 6th stage (PHMODE is floating) goes back to the 1st stage. Figure 3 shows the configuration for a 12 phase configuration +120 SVIN PHASE 3 CLKIN CLKOUT +180 PHMODE 180 CLKIN CLKOUT +120 PHMODE PHASE 5 300 CLKIN CLKOUT +120 PHMODE PHMODE PHASE 4 PHASE 2 CLKIN CLKOUT 4608 F02 PHASE 6 Figure 2. 6-Phase Operation 0 CLKIN CLKOUT 90 +90 PHMODE CLKIN CLKOUT 180 +90 PHMODE CLKIN CLKOUT +90 PHMODE CLKIN CLKOUT PHASE 4 PHASE 7 PHASE 10 120 210 300 (420) 60 CLKIN CLKOUT PHMODE CLKIN CLKOUT PHMODE PHASE 5 PHASE 8 +90 CLKIN CLKOUT +120 PHMODE PHASE 1 +90 (390) 30 270 +120 PHMODE PHASE 11 CLKIN CLKOUT PHMODE PHASE 3 CLKIN CLKOUT +90 PHMODE PHASE 2 150 +90 CLKIN CLKOUT +90 PHMODE PHASE 6 4608 F03 240 CLKIN CLKOUT PHMODE PHASE 9 330 +90 CLKIN CLKOUT PHMODE PHASE 12 Figure 3. 12-Phase Operation 4608f 13 LTM4608 APPLICATIONS INFORMATION the SGND at only one point. Figure 19 shows a schematic of the parallel design. The FB pins of the parallel module are tied together. With parallel operation, input and output capacitors may be reduced in part according to the operating duty cycle. frequency of operation (fundamental) and multiples of the operating frequency (harmonics). Spread Spectrum Operation To reduce this noise, the LTM4608 can run in spread spectrum operation by tying the CLKIN pin to SVIN. In spread spectrum operation, the LTM4608’s internal oscillator is designed to produce a clock pulse whose period is random on a cycle-by-cycle basis but fixed between 70% and 130% of the nominal frequency. This has the benefit of spreading the switching noise over a range of frequencies, thus significantly reducing the peak noise. Spread spectrum operation is disabled if CLKIN is tied to ground or if it’s driven by an external frequency synchronization signal. A capacitor value of 0.01μF must be placed from the PLLLPF pin to ground to control the slew rate of the spread spectrum frequency change. Switching regulators can be particularly troublesome where electromagnetic interference (EMI) is concerned. Output Voltage Tracking Switching regulators operate on a cycle-by-cycle basis to transfer power to an output. In most cases, the frequency of operation is fixed based on the output load. This method of conversion creates large components of noise at the Output voltage tracking can be programmed externally using the TRACK pin. The output can be tracked up and down with another regulator. The master regulator’s output is divided down with an external resistor divider that is the Input RMS Ripple Current Cancellation Application Note 77 provides a detailed explanation of multiphase operation. The input RMS ripple current cancellation mathematical derivations are presented, and a graph is displayed representing the RMS ripple current reduction as a function of the number of interleaved phases. Figure 4 shows this graph. 0.60 1-PHASE 2-PHASE 3-PHASE 4-PHASE 6-PHASE 0.55 0.50 RMS INPUT RIPPLE CURRENT DC LOAD CURRENT 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 DUTY FACTOR (VO/VIN) 4608 F04 Figure 4. Normalized Input RMS Ripple Current vs Duty Factor for One to Six Modules (Phases) 4608f 14 LTM4608 APPLICATIONS INFORMATION same as the slave regulator’s feedback divider to implement coincident tracking. The LTM4608 uses an accurate 10k resistor internally for the top feedback resistor. Figure 5 shows an example of coincident tracking: The track pin of the master can be controlled by an external ramp or by RSR and CSR in Figure 5 referenced to VIN. The RC ramp time can be programmed using equation: 0.596V t = – ln 1– • RSR • CSR VIN 10k Slave = 1+ • VTRACK R FB4 VTRACK is the track ramp applied to the slave’s track pin. VTRACK has a control range of 0V to 0.596V, or the internal reference voltage. When the Master’s output is divided down with the same resistor values used to set the slave’s output, this resistor divider is connected to the slave’s track pin. The slave will then coincident track with the master until it reaches its final value. The master will continue to its final value from the slave’s regulation point. Voltage tracking is disabled when VTRACK is more than 0.596V. RFB4 in Figure 5 will be equal to RFB2 for coincident tracking. OUTPUT VOLTAGE (V) MASTER OUTPUT SLAVE OUTPUT TIME 4608 F06 Figure 6 VIN 5V CLKIN VIN VOUT C2 100pF SVIN TIE TO VIN FOR DISABLE AND DEFAULT 100μs SOFT-START RSR SW RUN TRACK CSR LTM4608 RUN FB RFB1 2.21k ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN APPLY A CONTROL CLKOUT GND SGND RAMP WITH RSR AND CSR TIED TO VIN WHERE t = –(ln (1 – 0.596/VIN) • RSR • CSR) OR APPLY AN EXTERNAL TRACKING RAMP CLKIN VIN RFB3 10k RFB4 6.65k SW VOUT RUN TRACK LTM4608 RUN C3 22pF 3.3V C1 100μF SVIN MASTER 3.3V MASTER 3.3V 100μF 7A FB ITHM TRACK PGOOD MODE BSEL PHMODE MGN CLKOUT GND SGND SLAVE 1.5V C4 8A 100μF POSCAP RFB2 6.65k ITH PLLLPF + 1.5V 4608 F05 Figure 5. Dual Outputs (3.3V and 1.5V) with Tracking 4608f 15 LTM4608 APPLICATIONS INFORMATION Ratiometric tracking can be achieved by a few simple calculations and the slew rate value applied to the master’s track pin. As mentioned above, the TRACK pin has a control range from 0V to 0.596V. The master’s TRACK pin slew rate is directly equal to the master’s output slew rate in Volts/Time: MR • 10k = RFB3 SR where MR is the master’s output slew rate and SR is the slave’s output slew rate in Volts/Time. When coincident tracking is desired, then MR and SR are equal, thus RFB3 is equal the 10k. RFB4 is derived from equation: RFB4 = 0.596 V VFB VFB VTRACK + – 10k RFB2 RFB3 where VFB is the feedback voltage reference of the regulator and VTRACK is 0.596V. Since RFB3 is equal to the 10k top feedback resistor of the slave regulator in equal slew rate or coincident tracking, then RFB4 is equal to RFB2 with VFB = VTRACK. Therefore RFB3 = 10k and RFB4 = 6.65k in Figure 5. For applications that do not require tracking or sequencing, simply tie the TRACK pin to SVIN to let RUN control the turn on/off. Connecting TRACK to SVIN also enables the ~100μs of internal soft-start during start-up. Load current needs to be present during track down. Power Good The PGOOD pin is an open-drain pin that can be used to monitor valid output voltage regulation. This pin monitors a ±10% window around the regulation point. As shown in Figure 20, the sequencing function can be realized in a dual output application by controlling the RUN pins and the PGOOD signals from each other. The 1.5V output begins its soft starting after the PGOOD signal of 3.3V output becomes high, and 3.3V output starts its shut down after the PGOOD signal of 1.5V output becomes low. This can be applied to systems that require voltage sequencing between the core and sub-power supplies. Slope Compensation The module has already been internally compensated for all output voltages. Table 3 is provided for most application requirements. A spice model will be provided for other control loop optimization. For single module operation, connect ITHM pin to SGND. For parallel operation, tie ITHM pins together and then connect to SGND at one point. Tie ITH pins together to share currents evenly for all phases. 4.0 4.0 3.5 3.5 3.0 3.0 POWER LOSS (W) POWER LOSS (W) In ratiometric tracking, a different slew rate maybe desired for the slave regulator. RFB3 can be solved for when SR is slower than MR. Make sure that the slave supply slew rate is chosen to be fast enough so that the slave output voltage will reach it final value before the master output. For example: MR = 3.3V/ms and SR = 1.5V/ms. Then RFB3 = 22.1k. Solve for RFB4 to equal to 4.87k. 2.5 2.0 1.5 2.0 1.5 1.0 1.0 0.5 0 2.5 0.5 3.3VIN 1.5VOUT 3.3VIN 2.5VOUT 0 2 4 6 0 8 5VIN 1.5VOUT 5VIN 3.3VOUT 0 2 4 6 8 LOAD CURRENT (A) LOAD CURRENT (A) 4608 F07 Figure 7. 3.3VIN, 2.5V and 1.5VOUT Power Loss 4608 F08 Figure 8. 5VIN, 3.3V and 1.5VOUT Power Loss 4608f 16 LTM4608 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) APPLICATIONS INFORMATION 6 5 4 3 6 5 4 3 2 2 400LFM 200LFM 0LFM 1 0 40 50 400LFM 200LFM 0LFM 1 0 40 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608 F10 4608 F09 Figure 10. BGA Heat Sink with 3.3VIN to 1.5VOUT 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) Figure 9. No Heat Sink with 3.3VIN to 1.5VOUT 6 5 4 3 6 5 4 3 2 2 400LFM 200LFM 0LFM 1 0 40 50 400LFM 200LFM 0LFM 1 0 40 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608 F12 4608 F11 Figure 12. BGA Heat Sink with 5VIN to 1.5VOUT 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) Figure 11. No Heat Sink with 5VIN to 1.5VOUT 6 5 4 3 6 5 4 3 2 2 400LFM 200LFM 0LFM 1 0 40 50 400LFM 200LFM 0LFM 1 0 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608 F13 Figure 13. No Heat Sink with 3.3VIN to 2.5VOUT 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608 F14 Figure 14. BGA Heat Sink with 3.3VIN to 2.5VOUT 4608f 17 LTM4608 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) APPLICATIONS INFORMATION 6 5 4 3 2 0 40 50 5 4 3 2 400LFM 200LFM 0LFM 1 6 400LFM 200LFM 0LFM 1 0 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608 F15 4608 F16 Figure 15. No Heat Sink with 5VIN to 3.3VOUT Figure 16. BGA Heat Sink with 5VIN to 3.3VOUT Table 4. 1.5V Output DERATING CURVE VIN (V) POWER LOSS CURVE AIR FLOW (LFM) HEAT SINK θJA (°C/W) Figures 9, 11 3.3, 5 Figures 9, 11 3.3, 5 Figures 7, 8 0 None 25 Figures 7, 8 200 None 21 Figures 9, 11 3.3, 5 Figures 7, 8 400 None 20 Figures 10, 12 3.3, 5 Figures 7, 8 0 BGA Heat Sink 23.5 Figures 10, 12 3.3, 5 Figures 7, 8 200 BGA Heat Sink 22 Figures 10, 12 3.3, 5 Figures 7, 8 400 BGA Heat Sink 22 DERATING CURVE VIN (V) POWER LOSS CURVE AIR FLOW (LFM) HEAT SINK θJA (°C/W) Figure 15 5 Figure 8 0 None 25 Figure 15 5 Figure 8 200 None 21 Table 5. 3.3V Output Figure 15 5 Figure 8 400 None 20 Figure 16 5 Figure 8 0 BGA Heat Sink 23.5 Figure 16 5 Figure 8 200 BGA Heat Sink 22 Figure 16 5 Figure 8 400 BGA Heat Sink 22 4608f 18 LTM4608 APPLICATIONS INFORMATION Output Margining For a convenient system stress test on the LTM4608’s output, the user can program the LTM4608’s output to ±5%, ±10% or ±15% of its normal operational voltage. The margin pin with a voltage divider is driven with a small three-state gate as shown in Figure 18, for the three margin states (high, low, no margin). When the MGN pin is low, it forces negative margining in which the output voltage is below the regulation point. When MGN is high, the output voltage is forced to above the regulation point. The amount of output voltage margining is determined by the BSEL pin. When BSEL is low, it is 5%. When BSEL is high, it is 10%. When BSEL is floating, it is 15%. When margining is active, the internal output overvoltage and undervoltage comparators are disabled and PGOOD remains high. Margining is disabled by tying the MGN pin to VOUT. Thermal Considerations and Output Current Derating The power loss curves in Figures 7 and 8 can be used in coordination with the load current derating curves in Figures 9 to 16 for calculating an approximate θJA for the module with various heat sinking methods. Thermal models are derived from several temperature measurements at the bench, and thermal modeling analysis. Thermal Application Note 103 provides a detailed explanation of the analysis for the thermal models and the derating curves. Tables 4 and 5 provide a summary of the equivalent θJA for the noted conditions. These equivalent θJA parameters are correlated to the measured values and improve with air flow. The junction temperature is maintained at 125°C or below for the derating curves. electrical and thermal performance, some layout considerations are still necessary. • Use large PCB copper areas for high current path, including VIN, GND and VOUT. It helps to minimize the PCB conduction loss and thermal stress. • Place high frequency ceramic input and output capacitors next to the VIN, GND and VOUT pins to minimize high frequency noise. • Place a dedicated power ground layer underneath the unit. • To minimize the via conduction loss and reduce module thermal stress, use multiple vias for interconnection between top layer and other power layers. • Do not put vias directly on the pads, unless they are capped. • Use a separated SGND ground copper area for components connected to signal pins. Connect the SGND to GND underneath the unit. Figure 17 gives a good example of the recommended layout. GND VOUT COUT COUT GND COUT CIN Safety Considerations The LTM4608 modules do not provide isolation from VIN to VOUT. There is no internal fuse. If required, a slow blow fuse with a rating twice the maximum input current needs to be provided to protect each unit from catastrophic failure. Layout Checklist/Example The high integration of LTM4608 makes the PCB board layout very simple and easy. However, to optimize its VIN CIN GND 4608 F17 Figure 17. Recommended PCB Layout 4608f 19 LTM4608 APPLICATIONS INFORMATION CLKIN VIN 3V TO 5.5V CLKIN VIN CIN 10μF VOUT C1 220pF SVIN SW MODE COUT 100μF FB LTM4608 RUN PHMODE VOUT 2.5V 8A 8A AT 5V INPUT 6A AT 3.3V INPUT PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN C3 47pF RFB 3.09k ITH VIN 100k PGOOD BSEL CLKOUT GND SGND 50k VIN (HIGH = 10%) (FLOAT = 15%) (LOW = 5%) 1 50k VOUT 4 5 2 U1 U1: PERICON P1745T1G126CEX 3 OR TOSHIBA 7C75Z126AFE OE AIN 4608 F18 OE AIN VOUT MGN H H L H L X H L Z MARGIN VALUE H + OF BSEL SELECTION L – OF BSEL SELECTION NO MARGIN VIN/2 Figure 18. Typical 3V to 5.5VIN, 2.5V at 8A Design VIN 3V TO 5.5V CLKIN VIN 10μF TRACK C4 100pF SVIN SW RUN VOUT LTM4608 RUN FB 3.32k ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN VOUT CLKOUT GND SGND C2 10μF CLKIN VIN VOUT LTM4608 RUN C3 100μF 6.3V X5R C1 100μF 6.3V X5R SVIN SW 100μF 6.3V X5R VOUT 1.5V 16A FB ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN VOUT CLKOUT GND SGND 4608 F19 Figure 19. Two LTM4608s in Parallel, 1.5V at 16A Design 4608f 20 LTM4608 APPLICATIONS INFORMATION CLKIN VIN 5V CLKIN VIN VOUT C2 100pF SVIN D1 MMSD4148 SW SHDN FB LTM4608 RUN C3 22pF ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN 100k VOUT2 3.3V 7A RFB1 2.21k SHDN 3.3V CLKOUT GND SGND R1 100k 100μF 6.3V X5R 3.3V R2 100k 1.5V CLKIN VIN VOUT SVIN D2 MMSD4148 SW SHDN FB RFB2 6.65k ITH LTM4608 RUN C1 100μF 6.3V X5R + ITHM PLLLPF C4 100μF SANYO POSCAP 10mΩ VOUT1 1.5V 8A 100k TRACK PGOOD MODE BSEL PHMODE MGN 4608 F20 1.5V CLKOUT GND SGND Figure 20. Dual LTM4608 Output Sequencing Application CLKIN VIN 2.5V TO 5.5V CLKIN VIN 10μF 100pF SVIN SW LTM4608 RUN MODE PHMODE VOUT FB C1 100μF 6.3V X5R 10k ITH PLLLPF ITHM TRACK PGOOD MODE BSEL BSEL PHMODE MGN 1.2V CLKOUT GND SGND C2 100μF 6.3V X5R VOUT 1.2V/8A 5A AT 2.5V INPUT PGOOD 4608 F21 Figure 21. 2.5V to 5.5VIN, 1.2VOUT Design 4608f 21 VIN 5V 22 R5 31.6k R4 100k 3.3V TRACK OR RAMP CONTROL BSEL MGN MODE PHMODE MGN PHMODE VOUT2 VOUT1 C8 47pF C4 22pF R2 3.09k C7 220pF R10 2.21k C2 100pF C1 100μF 6.3V X5R VOUT2 2.5V 8A VOUT1 3.3V 100μF 7A 6.3V X5R R7 6.86k R6 100k 3.3V R9 49.9k R8 100k 3.3V MGN PHMODE CLKIN ITHM ITH FB VOUT CLKOUT GND SGND MGN BSEL PGOOD LTM4608 PHMODE MODE TRACK PLLLPF RUN SW SVIN VIN CLKOUT GND SGND BSEL MODE ITHM PGOOD ITH FB VOUT TRACK LTM4608 CLKIN PLLLPF RUN SW SVIN VIN Figure 22. 4-Phase, Four Outputs (3.3V, 2.5V, 1.8V and 1.5V) with Tracking CLKOUT GND SGND BSEL MODE PGOOD TRACK ITH FB VOUT ITHM LTM4608 CLKIN PLLLPF RUN SW SVIN VIN CLKOUT GND SGND ITHM PGOOD ITH FB VOUT TRACK LTM4608 CLKIN PLLLPF RUN SW SVIN VIN CLKIN 4608 F22 VOUT4 R8 6.65k VOUT3 R1 4.87k C8 100pF C5 100μF 6.3V X5R + C3 100μF 6.3V X5R C9 100μF 6.3V SANYO POSCAP 10mΩ VOUT4 1.5V 8A VOUT3 1.8V 8A LTM4608 APPLICATIONS INFORMATION 4608f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 3.810 2.540 1.270 0.381 0.000 0.381 1.270 2.540 SUGGESTED PCB LAYOUT TOP VIEW 1.270 PACKAGE TOP VIEW 0.381 0.000 0.381 5.080 X 9.00 BSC Y aaa Z 2.400 – 2.600 DETAIL A MOLD CAP Z DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PAD #1 IDENTIFIER MAY BE EITHER A MOLD OR A MARKED FEATURE 4 SYMBOL TOLERANCE 0.15 aaa 0.10 bbb 6. THE TOTAL NUMBER OF PADS: 68 5. PRIMARY DATUM -Z- IS SEATING PLANE LAND DESIGNATION PER JESD MO-222 3 2. ALL DIMENSIONS ARE IN MILLIMETERS TRAY PIN 1 BEVEL COMPONENT PIN “A1” 3 PADS SEE NOTES 1.27 BSC 0.737 – 0.787 7.620 BSC 0.290 – 0.350 SUBSTRATE NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 DETAIL A PACKAGE SIDE VIEW 2.69 – 2.95 (Reference LTC DWG # 05-08-1808 Rev A) bbb Z aaa Z 3.810 4 1.270 PAD “A1” CORNER 6.350 15.00 BSC 6.350 5.080 3.810 2.540 2.540 3.810 LGA Package 68-Lead (15mm × 9mm × 2.82mm) 11 10 8 7 6 5 PACKAGE BOTTOM VIEW 4 3 LGA 68 0607 REV A PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX μModule 9 12.70 BSC 0.737 – 0.787 2 1 PAD 1 A B C D E F G LTM4608 PACKAGE DESCRIPTION 4608f 23 LTM4608 PACKAGE DESCRIPTION Pin Assignment Table (Arranged by Pin Number) PIN NAME PIN NAME PIN NAME C1 VIN PIN NAME A1 GND B1 GND A2 GND B2 – C2 – A3 GND B3 CLKIN C3 SW A4 GND B4 PHMODE C4 SW D4 D1 PIN NAME PIN NAME PIN NAME VIN E1 SGND F1 RUN G1 GND D2 – E2 – F2 CLKOUT G2 GND D3 VIN E3 PLLLPF F3 GND G3 GND VIN E4 – F4 SVIN G4 GND A5 GND B5 MODE C5 SW D5 VIN E5 TRACK F5 ITHM G5 GND A6 GND B6 – C6 – D6 – E6 – F6 ITH G6 GND A7 GND B7 BSEL C7 PGOOD D7 VIN E7 FB F7 GND G7 GND A8 GND B8 MGN C8 VIN D8 VIN E8 VIN F8 GND G8 GND A9 GND B9 GND C9 VIN D9 VIN E9 VOUT F9 VOUT G9 VOUT A10 GND B10 GND C10 VOUT D10 VOUT E10 VOUT F10 VOUT G10 VOUT A11 GND B11 GND C11 VOUT D11 VOUT E11 VOUT F11 VOUT G11 VOUT RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC2900 Quad Supply Monitor with Adjustable Reset Timer Monitors Four Supplies; Adjustable Reset Timer LTC2923 Power Supply Tracking Controller Tracks Both Up and Down; Power Supply Sequencing LT3825/LT3837 Synchronous Isolated Flyback Controllers No Optocoupler Required; 3.3V, 12A Output; Simple Design LTM4600 10A DC/DC μModule Basic 10A DC/DC μModule, LGA Package LTM4600HVMP Military Plastic 10A DC/DC μModule Guaranteed Operation from –55°C to 125°C Ambient, LGA Package LTM4601/ LTM4601A 12A DC/DC μModule with PLL, Output Tracking/ Margining and Remote Sensing Synchronizable, PolyPhase Operation, LTM4601-1/LTM4601A-1 Version has no Remote Sensing, LGA Package LTM4602 6A DC/DC μModule Pin Compatible with the LTM4600, LGA Package LTM4603 6A DC/DC μModule with PLL and Outpupt Tracking/ Synchronizable, PolyPhase Operation, LTM4603-1 Version have no Remote Margining and Remote Sensing Sensing, Pin Compatible with the LTM4601, LGA Package LTM4604 Low VIN 4A DC/DC μModule 2.375V ≤ VIN ≤ 5.5V, 0.8V ≤ VOUT ≤ 5V, 9mm × 15mm × 2.3mm LGA Package 4608f 24 Linear Technology Corporation LT 0907 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2007