LTM4605 High Efficiency Buck-Boost DC/DC µModule FEATURES DESCRIPTION n The LTM®4605 is a high efficiency switching mode buckboost power supply. Included in the package are the switching controller, power FETs, and support components. Operating over an input voltage range of 4.5V to 20V, the LTM4605 supports an output voltage range of 0.8V to 16V, set by a resistor. This high efficiency design delivers up to 5A continuous current in boost mode (12A in buck mode). Only the inductor, sense resistor, bulk input and output capacitors are needed to finish the design. n n n n n n n n n n n Single Inductor Architecture Allows VIN Above, Below or Equal to VOUT Wide VIN Range: 4.5V to 20V Wide VOUT Range: 0.8V to 16V 5A DC Typical (12A DC Typical at Buck Mode) High Efficiency Up to 98% Current Mode Control Power Good Output Signal Phase-Lockable Fixed Frequency: 200kHz to 400kHz Ultra-Fast Transient Response Current Foldback Protection Output Overvoltage Protection Small, Low Profile Surface Mount LGA Package (15mm × 15mm × 2.8mm) The low profile package enables utilization of unused space on the bottom of PC boards for high density point of load regulation. The high switching frequency and current mode architecture enable a very fast transient response to line and load changes. The LTM4605 can be frequency synchronized with an external clock to reduce undesirable frequency harmonics. APPLICATIONS n n n Telecom, Servers and Networking Equipment Industrial and Automotive Equipment High Power Battery-Operated Devices Fault protection features include overvoltage and foldback current protection. The DC/DC μModule™ is offered in a small and thermally enhanced 15mm × 15mm × 2.8mm LGA package. The LTM4605 is Pb-free and RoHS compliant. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark 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 and Power Loss vs Input Voltage 12V/5A Buck-Boost DC/DC μModule with 4.5V to 20V Input 99 CLOCK SYNC 10μF 35V VIN PLLIN V OUT RUN LTM4605 4.7μH SW1 SW2 RSENSE SENSE+ 0.1μF 6mΩ SENSE– SS SGND PGND 330μF 25V VOUT 12V 5A 98 8 VOUT = 12V ILOAD = 5A f = 200kHz 7 97 6 96 5 95 4 94 3 93 2 92 1 91 VFB POWER LOSS (W) 10μF 35V FCB ON/OFF + EFFICIENCY (%) VIN 4.5V TO 20V 90 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 VIN (V) 7.15k 4605 TA01 4605 TA01b 4605fa 1 LTM4605 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (See Table 6. Pin Assignment) VIN ............................................................. –0.3V to 20V VOUT ............................................................. 0.8V to 16V INTVCC, EXTVCC, RUN, SS, PGOOD .............. –0.3V to 7V SW1, SW2 .................................................... –5V to 20V VFB, COMP ................................................ –0.3V to 2.4V FCB, STBYMD ....................................... –0.3V to INTVCC PLLIN ........................................................ –0.3V to 5.5V PLLFLTR.................................................... –0.3V to 2.7V Operating Temperature Range (Note 2) ...............................................–40°C to 85°C Junction Temperature ........................................... 125°C Storage Temperature Range...................–55°C to 125°C TOP VIEW BANK 2 M L BANK 4 BANK 1 K J H BANK 3 G BANK 5 F E D C BANK 6 B A 1 2 3 4 5 6 7 8 9 10 11 12 LGA PACKAGE 141-LEAD (15mm s 15mm s 2.8mm) TJMAX = 125°C, θJP = 4°C/W WEIGHT = 1.5g ORDER INFORMATION LEAD FREE FINISH PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTM4605EV#PBF LTM4605V 141-Lead (15mm × 15mm × 2.8mm) LGA –40°C to 85°C LTM4605IV#PBF LTM4605V 141-Lead (15mm × 15mm × 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 l denotes the specifications which apply over the –40°C to 85°C temperature range, otherwise specifications are at TA = 25°C, VIN = 12V. Per typical application (front page) configuration. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Input Specifications Input DC Voltage l VIN(UVLO) Undervoltage Lockout Threshold VIN Falling l IQ(VIN) Input Supply Bias Current Normal Standby Shutdown Supply Current VRUN = 0V, VSTBYMD > 2V VRUN = 0V, VSTBYMD = Open VIN(DC) 4.5 3.4 2.8 1.6 35 20 V 4 V 60 mA mA μA 4605fa 2 LTM4605 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the –40°C to 85°C temperature range, otherwise specifications are at TA = 25°C, VIN = 12V. Per typical application (front page) configuration. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Output Specifications IOUTDC Output Continuous Current Range VIN = 12V, VOUT = 5V (See Output Current Derating Curves VIN = 6V, VOUT = 12V for Different VIN, VOUT and TA) ΔVFB/VFB(NOM) Reference Voltage Line Regulation Accuracy VIN = 4.5V to 20V, VCOMP = 1.2V (Note 3) ΔVFB/VFB(LOAD) Load Regulation Accuracy VCOMP = 1.2V to 0.7V VCOMP = 1.2V to 1.8V (Note 3) M1 tr Turn-On Time (Note 4) Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 50 ns M1 tf Turn-Off Time Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 40 ns M3 tr Turn-On Time Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 25 ns M3 tf Turn-Off Time Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 20 ns M2, M4 tr Turn-On Time Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 20 ns M2, M4 tf Turn-Off Time Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 20 ns t1d M1 Off to M2 On Delay (Note 4) Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 50 ns t2d M2 Off to M1 On Delay Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 50 ns t3d M3 Off to M4 On Delay Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 50 ns t4d M4 Off to M3 On Delay Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 50 ns Mode Transition 1 M2 Off to M4 On Delay Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 220 ns Mode Transition 2 M4 Off to M2 On Delay Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA 220 ns M1 RDS(ON) Static Drain-to-Source OnResistance Bias Current ISW = 3A 6.5 mΩ M2 RDS(ON) Static Drain-to-Source OnResistance Bias Current ISW = 3A 8 12 mΩ M3 RDS(ON) Static Drain-to-Source OnResistance Bias Current ISW = 3A 8 12 mΩ M4 RDS(ON) Static Drain-to-Source OnResistance Bias Current ISW = 3A 8 12 mΩ 12 5 l l A A 0.002 0.02 % 0.15 –0.15 0.5 –0.5 % % Switch Section Oscillator and Phase-Locked Loop fNOM Nominal Frequency VPLLFLTR = 1.2V 260 300 330 kHz fLOW Lowest Frequency VPLLFLTR = 0V 170 200 220 kHz fHIGH Highest Frequency VPLLFLTR = 2.4V 340 400 440 kHz RPLLIN PLLIN Input Resistance IPLLFLTR Phase Detector Output Current fPLLIN < fOSC fPLLIN > fOSC 50 kΩ –15 15 μA μA 4605fa 3 LTM4605 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the –40°C to 85°C temperature range, otherwise specifications are at TA = 25°C, VIN = 12V. Per typical application (front page) configuration. SYMBOL PARAMETER CONDITIONS VFB Feedback Reference Voltage VCOMP = 1.2V VRUN RUN Pin ON/OFF Threshold ISS Soft-Start Charging Current VRUN = 2.2V MIN TYP MAX UNITS 0.792 0.8 0.808 V 1 1.6 2.2 V 1 1.7 Control Section l VSTBYMD(START) Start-Up Threshold VSTBYMD Rising VSTBYMD(KA) Keep-Active Power On Threshold VSTBYMD Rising, VRUN = 0V 0.4 VFCB Forced Continuous Threshold IFCB Forced Continuous Pin Current VFCB = 0.85V VBURST Burst Inhibit (Constant Frequency) Threshold DF(BOOST, MAX) μA 0.7 V 1.25 V 0.76 0.8 0.84 V –0.3 –0.2 –0.1 μA Measured at FCB Pin 5.3 5.5 V Maximum Duty Factor % Switch M4 On 99 DF(BUCK, MAX) Maximum Duty Factor % Switch M1 On tON(MIN, BUCK) Minimum On-Time for Synchronous Switch M1 (Note 5) Switch in Buck Operation RFBHI Resistor Between VOUT and VFB pins % 99 % 200 250 ns 99.5 100 100.5 kΩ l 5.7 6 6.3 V 0.3 2 % l 5.4 5.6 V 300 mV Internal VCC Regulator INTVCC Internal VCC Voltage VIN > 7V, VEXTVCC = 5V ΔVLDO/VLDO Internal VCC Load Regulation ICC = 0mA to 20mA, VEXTVCC = 5V VEXTVCC EXTVCC Switchover Voltage ICC = 20mA, VEXTVCC Rising ΔVEXTVCC(HYS) EXTVCC Switchover Hysteresis ΔVEXTVCC EXTVCC Switch Drop Voltage ICC = 20mA, VEXTVCC = 6V 60 150 mV 160 –130 190 –150 mV mV Current Sensing Section VSENSE(MAX) Maximum Current Sense Threshold l l Boost Mode Buck Mode –95 VSENSE(MIN, BUCK) Minimum Current Sense Threshold Discontinuous Mode ISENSE Sense Pins Total Source Current VSENSE– = VSENSE+ = 0V –6 mV –380 μA ΔVFBH PGOOD Upper Threshold VFB Rising 5.5 7.5 10 % ΔVFBL PGOOD Lower Threshold VFB Falling –5.5 –7.5 –10 % ΔVFB(HYS) PGOOD Hysteresis VFB Returning 2.5 VPGL PGOOD Low Voltage IPGOOD = 2mA 0.2 IPGOOD PGOOD Leakage Current VPGOOD = 5V PGOOD 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. Note 2: The LTM4605E 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 % 0.3 V 1 μA with statistical process controls. The LTM4605I is guaranteed over the –40°C to 85°C temperature range. Note 3: The LTM4605 is tested in a feedback loop that servos VCOMP to a specified voltage and measures the resultant VFB. Note 4: Turn-on and turn-off time are measured using 10% and 90% levels. Transition delay time is measured using 50% levels. Note 5: 100% tested at wafer level only. 4605fa 4 LTM4605 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current 12VIN to 12VOUT 90 80 80 70 70 EFFICIENCY (%) 100 90 EFFICIENCY (%) 100 60 50 40 95 85 75 60 50 40 30 65 55 45 30 20 0 0.01 0.1 1 LOAD CURRENT (A) 35 20 CCM DCM BURST 10 CCM DCM BURST 10 0 0.01 10 0.1 1 LOAD CURRENT (A) 4605 G01 15 0.01 10 100 95 95 95 90 90 85 85 EFFICIENCY (%) 75 EFFICIENCY (%) 100 90 80 75 70 65 70 18VIN TO 5VOUT 12VIN TO 5VOUT 5VIN TO 5VOUT 65 60 0 3 6 9 LOAD CURRENT (A) 12 80 75 70 65 60 18VIN TO 3.3VOUT 12VIN TO 3.3VOUT 5VIN TO 3.3VOUT 55 50 0 3 6 9 LOAD CURRENT (A) 4605 G04 12 60 18VIN TO 2.5VOUT 12VIN TO 2.5VOUT 5VIN TO 2.5VOUT 55 50 0 IOUT 2A/DIV IOUT 2A/DIV VOUT 200mV/DIV VOUT 200mV/DIV VOUT 100mV/DIV 200μs/DIV 12 Transient Response from 18VIN to 12VOUT IOUT 2A/DIV LOAD STEP: 0A TO 3A AT CCM OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND 2x 180μF ELECTROLYTIC CAPS 2x 15mΩ SENSING RESISTORS 6 9 LOAD CURRENT (A) 4605 G06 Transient Response from 12VIN to 12VOUT 4605 G07 3 4605 G05 Transient Response from 6VIN to 12VOUT 200μs/DIV 100 Efficiency vs Load Current 1.5μH Inductor (CCM) 100 80 0.1 1 10 LOAD CURRENT (A) 4605 G03 Efficiency vs Load Current 1.5μH Inductor (CCM) 85 CCM DCM SKIP CYCLE 25 4605 G02 Efficiency vs Load Current 3.3μH Inductor (CCM) EFFICIENCY (%) Efficiency vs Load Current 18VIN to 12VOUT EFFICIENCY (%) Efficiency vs Load Current 6VIN to 12VOUT (Refer to Figure 16) 4605 G08 LOAD STEP: 0A TO 3A AT CCM OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND 2x 180μF ELECTROLYTIC CAPS 2x 15mΩ SENSING RESISTORS 200μs/DIV 4605 G09 LOAD STEP: 0A TO 4A AT CCM OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND 2x 180μF ELECTROLYTIC CAPS 2x 15mΩ SENSING RESISTORS 4605fa 5 LTM4605 TYPICAL PERFORMANCE CHARACTERISTICS Start-Up with 6VIN to 12VOUT at IOUT = 5A Start-Up with 18VIN to 12VOUT at IOUT = 5A VOUT 5V/DIV VOUT 5V/DIV IIN 5A/DIV IIN 2A/DIV IL 5A/DIV IL 5A/DIV 50ms/DIV 4605 G10 50ms/DIV 4605 G11 0.22μF SOFT-START CAP OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND 2x 180μF ELECTROLYTIC CAPS 2x 15mΩ SENSING RESISTORS 0.22μF SOFT-START CAP OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND 2x 180μF ELECTROLYTIC CAPS 2x 15mΩ SENSING RESISTORS Short Circuit with 6VIN to 12VOUT at IOUT = 5A Short Circuit with 18VIN to 12VOUT at IOUT = 5A VOUT 5V/DIV VOUT 10V/DIV IIN 5A/DIV IIN 10A/DIV 20μs/DIV 4605 G12 OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND 2x 180μF ELECTROLYTIC CAPS 2x 15mΩ SENSING RESISTORS 100μs/DIV 4605 G13 OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND 2x 180μF ELECTROLYTIC CAPS 2x 15mΩ SENSING RESISTORS 4605fa 6 LTM4605 PIN FUNCTIONS VIN (Bank 1): Power Input Pins. Apply input voltage between these pins and PGND pins. Recommend placing input decoupling capacitance directly between VIN pins and PGND pins. VOUT (Bank 5): Power Output Pins. Apply output load between these pins and PGND pins. Recommend placing output decoupling capacitance directly between these pins and PGND pins. PGND (Bank 6): Power Ground Pins for Both Input and Output Returns. SW1, SW2 (Bank 4, Bank 2): Switch Nodes. The power inductor is connected between SW1 and SW2. RSENSE (Bank 3): Sensing Resistor Pin. The sensing resistor is connected from this pin to PGND. SENSE+ (Pin A4): Positive Input to the Current Sense and Reverse Current Detect Comparators. SENSE– (Pin A5): Negative Input to the Current Sense and Reverse Current Detect Comparators. EXTVCC (Pin F6): External VCC Input. When EXTVCC exceeds 5.7V, an internal switch connects this pin to INTVCC and shuts down the internal regulator so that the controller and gate drive power is drawn from EXTVCC. Do not exceed 7V at this pin and ensure that EXTVCC < VIN. INTVCC (Pin F5): Internal 6V Regulator Output. This pin is for additional decoupling of the 6V internal regulator. PLLIN (Pin B9): External Clock Synchronization Input to the Phase Detector. This pin is internally terminated to SGND with a 50k resistor. The phase-locked loop will force the rising bottom gate signal of the controller to be synchronized with the rising edge of PLLIN signal. PLLFLTR (Pin B8): The lowpass filter of the phase-locked loop is tied to this pin. This pin can also be used to set the frequency of the internal oscillator with an AC or DC voltage. See the Applications Information section for details. STBYMD (Pin A10): LDO Control Pin. Determine whether the internal LDO remains active when the controller is shut down. See Operations section for details. If the STBYMD pin is pulled to ground, the SS pin is internally pulled to ground to disable start-up and thereby providing a single control pin for turning off the controller. An internal decoupling capacitor is tied to this pin. VFB (Pin B6): The Negative Input of the Error Amplifier. Internally, this pin is connected to VOUT with a 100k precision resistor. Different output voltages can be programmed with an additional resistor between VFB and SGND pins. See the Applications Information section. FCB (Pin A9): Forced Continuous Control Input. The voltage applied to this pin sets the operating mode of the module. When the applied voltage is less than 0.8V, the forced continuous current mode is active in boost operation and the skip cycle mode is active in buck operation. When the pin is tied to INTVCC, the constant frequency discontinuous current mode is active in buck or boost operation. See the Applications Information section. SGND (Pin A7): Signal Ground Pin. This pin connects to PGND at output capacitor point. COMP (Pin B7): Current Control Threshold and Error Amplifier Compensation Point. The current comparator threshold increases with this control voltage. The voltage ranges from 0V to 2.4V. PGOOD (Pin B5): 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, after a 25μs power bad mask timer expires. RUN (Pin A8): Run Control Pin. A voltage below 1.6V will turn off the module. There is a 100k resistor between the RUN pin and SGND in the module. Do not apply more than 6V to this pin. See Applications Information section. SS (Pin A6): Soft-Start Pin. Soft-start reduces the input power sources’ surge currents by gradually increasing the controller’s current limit. 4605fa 7 LTM4605 SIMPLIFIED BLOCK DIAGRAM VIN 4.5V TO 20V EXTVCC C1 CIN M1 SW2 INTVCC M2 PGOOD L SW1 RUN ON/OFF VOUT 100k 12V 5A STBYMD CO1 M3 COUT 0.1μF 100k COMP VFB M4 INT COMP CONTROLLER RFB 7.15k RSENSE SENSE+ SS SS 0.1μF PLLIN INT FILTER RSENSE SENSE– PLLFLTR PGND INT FILTER FCB SGND 1000pF TO PGND PLANE AS SHOWN IN FIGURE 13 4605 BD Figure 1. Simplified LTM4605 Block Diagram DECOUPLING REQUIREMENTS TA = 25°C. Use Figure 1 configuration. SYMBOL PARAMETER CONDITIONS CIN External Input Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 12V) IOUT = 5A MIN 10 COUT External Output Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 12V) IOUT = 5A 200 TYP MAX UNITS μF 300 μF 4605fa 8 LTM4605 OPERATION Power Module Description The LTM4605 is a non-isolated buck-boost DC/DC power supply. It can deliver a wide range output voltage from 0.8V to 16V over a wide input range from 4.5V to 20V, by only adding the sensing resistor, inductor and some external input and output capacitors. It provides precisely regulated output voltage programmable via one external resistor. The typical application schematic is shown in Figure 16. The LTM4605 has an integrated current mode buck-boost control, ultralow RDS(ON) FETs with fast switching speed and integrated Schottky diodes. With current mode control and internal feedback loop compensation, the LTM4605 module has sufficient stability margins and good transient performance under a wide range of operating conditions and with a wide range of output capacitors. The frequency of LTM4605 can be operated from 200kHz to 400kHz by setting the voltage on the PLLFLTR pin. Alternatively, its frequency can be synchronized by the input clock signal from the PLLIN pin. The typical switching frequency is 400kHz. The Burst Mode and skip-cycle mode operations can be enabled at light loads in the LTM4605 to improve its efficiency, while the forced continuous mode and discontinuous mode operations are used for constant frequency applications. Foldback current limiting is activated in an overcurrent condition as VFB drops. Internal overvoltage and undervoltage comparators pull the open-drain PGOOD output low if the output feedback voltage exits the ±10% window around the regulation point. Pulling the RUN pin below 1.6V forces the controller into its shutdown state. If an external bias supply is applied on the EXTVCC pin, then an efficiency improvement will occur due to the reduced power loss in the internal linear regulator. This is especially true at the higher input voltage range. APPLICATIONS INFORMATION The typical LTM4605 application circuit is shown in Figure 16. 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. Table 1. RFB Resistor (0.5%) vs Various Output Voltages VOUT 0.8V 1.5V 2.5V 3.3V 5V 6V RFB Open 115k 47.5k 32.4k 19k 15.4k VOUT 8V 9V 10V 12V 15V 16V RFB 11k 9.76k 8.66k 7.15k 5.62k 5.23k Output Voltage Programming The PWM controller has an internal 0.8V±1% reference voltage. As shown in the Block Diagram, a 100k, 0.5% internal feedback resistor connects VOUT and VFB pins together. Adding a resistor RFB from the VFB pin to the SGND pin programs the output voltage: VOUT = 0.8 V • 100k + RFB RFB Operation Frequency Selection The LTM4605 uses current mode control architecture at constant switching frequency, which is determined by the internal oscillator’s capacitor. This internal capacitor is charged by a fixed current plus an additional current that is proportional to the voltage applied to the PLLFLTR pin. 4605fa 9 LTM4605 APPLICATIONS INFORMATION The PLLFLTR pin can be grounded to lower the frequency to 200kHz or tied to 2.4V to yield approximately 400kHz. When PLLIN is left open, the PLLFLTR pin goes low, forcing the oscillator to its minimum frequency. A graph for the voltage applied to the PLLFLTR pin vs frequency is given in Figure 2. As the operating frequency increases, the gate charge losses will be higher, thus the efficiency is low. The maximum switching frequency is approximately 400kHz. 450 OPERATING FREQUENCY (kHz) 400 350 300 250 200 150 100 50 0 0 1.0 1.5 2.0 0.5 PLLFLTR PIN VOLTAGE (V) 2.5 4605 F02 Figure 2. Frequency vs PLLFLTR Pin Voltage FREQUENCY SYNCHRONIZATION The LTM4605 can also be synchronized to an external source via the PLLIN pin instead of adjusting the voltage on the PLLFLTR pin directly. The power module has a phaselocked loop comprised of an internal voltage controlled oscillator and a phase detector. This allows turning on the internal top MOSFET for locking to the rising edge of the external clock. A pulse detection circuit is used to detect a clock on the PLLIN pin to turn on the phase lock loop. The input pulse width of the clock has to be at least 400ns, and 2V in amplitude. The synchronized frequency ranges from 200kHz to 400kHz, corresponding to a DC voltage input from 0V to 2.4V at PLLFLTR. During the start up of the regulator, the phase-lock loop function is disabled. Low Current Operation To improve the efficiency at low current operation, LTM4605 provides three modes for both buck and boost operations by accepting a logic input on the FCB pin. Table 2 shows the different operation modes. Table 2. Different Operating Modes FCB PIN BUCK BOOST 0V to 0.75V Force Continuous Mode Force Continuous Mode 0.85V to 5V Skip-Cycle Mode Burst Mode Operation >5.3V DCM with Constant Freq DCM with Constant Freq When the FCB pin voltage is lower than 0.8V, the controller behaves as a continuous, PWM current mode synchronous switching regulator. When the FCB pin voltage is below VINTVCC – 1V, but greater than 0.8V, the controller enters Burst Mode operation in boost operation or enters skipcycle mode in buck operation. During boost operation, Burst Mode operation is activated if the load current is lower than the preset minimum output current level. The MOSFETs will turn on for several cycles, followed by a variable “sleep” interval depending upon the load current. During buck operation, skip-cycle mode sets a minimum positive inductor current level. In this mode, some cycles will be skipped when the output load current drops below 1% of the maximum designed load in order to maintain the output voltage. When the FCB pin is tied to the INTVCC pin, the controller enters constant frequency discontinuous current mode (DCM). For boost operation, if the output voltage is high enough, the controller can enter the continuous current buck mode for one cycle to discharge inductor current. In the following cycle, the controller will resume DCM boost operation. For buck operation, constant frequency discontinuous current mode is turned on if the preset minimum negative inductor current level is reached. At very light loads, this constant frequency operation is not as efficient as Burst Mode operation or skip-cycle, but does provide low noise, constant frequency operation. Input Capacitors In boost mode, since the input current is continuous, only minimum input capacitors are required. However, the input current is discontinuous in buck mode, so the selection of input capacitor CIN is driven by the need of filtering the input square wave current. 4605fa 10 LTM4605 APPLICATIONS INFORMATION For a buck converter, the switching duty-cycle can be estimated as: D= 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. CIN can be a switcher-rated electrolytic aluminum capacitor, OS-CON capacitor or high volume ceramic capacitors. Note the capacitor ripple current ratings are often based on temperature and hours of life. This makes it advisable to properly derate the input capacitor, or choose a capacitor rated at a higher temperature than required. Always contact the capacitor manufacturer for derating requirements. Output Capacitors Inductor Selection The inductor is chiefly decided by the required ripple current and the operating frequency. The inductor current ripple ΔIL is typically set to 20% to 40% of the maximum inductor current. In the inductor design, the worst cases in continuous mode are considered as follows: LBOOST ≥ In boost mode, the discontinuous current shifts from the input to the output, so the output capacitor COUT must be capable of reducing the output voltage ripple. For boost and buck modes, the steady ripple due to charging and discharging the bulk capacitance is given by: VRIPPLE,BOOST = VRIPPLE,BUCK = The LTM4605 is designed for low output voltage ripple. The bulk output capacitors defined as COUT are chosen with low enough ESR to meet the output voltage ripple and transient requirements. COUT can be a low ESR tantalum capacitor, a low ESR polymer capacitor or a ceramic capacitor. Multiple capacitors can be placed in parallel to meet the ESR and RMS current handling requirements. The typical capacitance is 300μF. Additional output filtering may be required by the system designer, if further reduction of output ripple or dynamic transient spike is required. Table 3 shows a matrix of different output voltages and output capacitors to minimize the voltage droop and overshoot at a current transient. ( IOUT(MAX ) • VOUT − VIN(MIN) ) COUT • VOUT • f ( VOUT • VIN(MAX ) − VOUT ) 8 • L • COUT • VIN(MAX ) • f 2 The steady ripple due to the voltage drop across the ESR (effective series resistance) is given by: VESR,BUCK = ΔIL(MAX ) • ESR VESR,BOOST = IL(MAX ) • ESR LBUCK ≥ ( VIN • VOUT(MAX ) − VIN ) VOUT(MAX ) • f • IOUT(M MAX ) • Ripple% ( VOUT • VIN(MAX ) − VOUT ) VIN(MAX ) • f • IOUT(MAX ) • Ripple% where: f is operating frequency, Hz Ripple% is allowable inductor current ripple, % VOUT(MAX) is maximum output voltage, V VIN(MAX) is maximum input voltage, V VOUT is output voltage, V IOUT(MAX) is maximum output load current, A The inductor should have low DC resistance to reduce the I2R losses, and must be able to handle the peak inductor current without saturation. To minimize radiated noise, use a toroid, pot core or shielded bobbin inductor. Please refer to Table 3 for the recommended inductors for different cases. 4605fa 11 LTM4605 APPLICATIONS INFORMATION RSENSE Selection and Maximum Output Current RSENSE is chosen based on the required inductor current. Since the maximum inductor valley current at buck mode is much lower than the inductor peak current at boost mode, different sensing resistors are suggested to use in buck and boost modes. The current comparator threshold sets the peak of the inductor current in boost mode and the maximum inductor valley current in buck mode. In boost mode, the allowed maximum average load current is: ⎛ 160mV ΔIL ⎞ VIN IOUT(MAX,BOOST) = ⎜ − • 2 ⎟⎠ VOUT ⎝ RSENSE where ΔIL is peak-to-peak inductor ripple current. In buck mode, the allowed maximum average load current is: IOUT(MAX,BUCK ) = 130mV ΔIL + RSENSE 2 The maximum current sensing RSENSE value for the boost mode is: the internal reference and the output voltage. The total soft-start time can be calculated as: t SOFTSTART = 2.4V • CSS 1.7µA When the RUN pin falls below 1.6V, then soft-start pin is reset to allow for proper soft-start control when the regulator is enabled again. Current foldback and force continuous mode are disabled during the soft-start process. The softstart function can also be used to control the output ramp up time, so that another regulator can be easily tracked. Do not apply more than 6V to the SS pin. Run Enable The RUN pin is used to enable the power module. The pin can be driven with a logic input, and not exceed 6V. The RUN pin can also be used as an undervoltage lockout (UVLO) function by connecting a resistor from the input supply to the RUN pin. The equation: V _ UVLO = R + 100k • 1.6 V 100k RSENSE(MAX,BOOST) = Power Good 2 • 160mV • VIN 2 • IOUT(MAX,BOOST) • VOUT + ΔIL • VIN The PGOOD pin is an open drain pin that can be used to monitor valid output voltage regulation. This pin monitors a ±7.5% window around the regulation point, and tracks with margining. The maximum current sensing RSENSE value for the buck mode is: RSENSE(MAX,BUCK ) = 2 • 130mV 2 • IOUT(MAX,BUCK ) – ΔIL A 20% to 30% margin on the calculated sensing resistor is usually recommended. Please refer to Table 3 for the recommended sensing resistors for different applications. Soft-Start The SS pin provides a means to soft-start the regulator. A capacitor on this pin will program the ramp rate of the output voltage. A 1.7μA current source will charge up the external soft-start capacitor. This will control the ramp of COMP Pin This pin is the external compensation pin. The module has already been internally compensated for most output voltages. A spice model will be provided for other control loop optimization. Fault Conditions: Current Limit and Overcurrent Foldback LTM4605 has a current mode controller, which inherently limits the cycle-by-cycle inductor current not only in steady state operation, but also in transient. Refer to Table 3. To further limit current in the event of an overload condition, the LTM4605 provides foldback current limiting. If the 4605fa 12 LTM4605 APPLICATIONS INFORMATION output voltage falls by more than 70%, then the maximum output current is progressively lowered to about 30% of its full current limit value for boost mode and about 40% for buck mode. Standby Mode (STBYMD) The standby mode (STBYMD) pin provides several choices for start-up and standby operational modes. If the pin is pulled to ground, the SS pin is internally pulled to ground, preventing start-up and thereby providing a single control pin for turning off the controller. If the pin is left open or decoupled with a capacitor to ground, the SS pin is internally provided with a starting current, permitting external control for turning on the controller. If the pin is connected to a voltage greater than 1.25V, the internal regulator (INTVCC) will be on even when the controller is shut down (RUN pin voltage <1.6V). In this mode, the onboard 6V linear regulator can provide power to keep-alive functions such as a keyboard controller. INTVCC and EXTVCC An internal P-channel low dropout regulator produces 6V at the INTVCC pin from the VIN supply pin. INTVCC powers the control chip and internal circuitry within the module. The LTM4605 also provides the external supply voltage pin EXTVCC. When the voltage applied to EXTVCC rises above 5.7V, the internal regulator is turned off and an internal switch connects the EXTVCC pin to the INTVCC pin thereby supplying internal power. The switch remains close as long as the voltage applied to EXTVCC remains above 5.5V. This allows the MOSFET driver and control power to be derived from the output when (5.7V < VOUT < 7V) and from the internal regulator when the output is out of regulation (startup, short-circuit). If more current is required through the EXTVCC switch than is specified, an external Schottky diode can be interposed between the EXTVCC and INTVCC pins. Ensure that EXTVCC ≤ VIN. The following list summarizes the three possible connections for EXTVCC: 1. EXTVCC left open (or grounded). This will cause INTVCC to be powered from the internal 6V regulator at the cost of a small efficiency penalty. 2. EXTVCC connected directly to VOUT (5.7V < VOUT < 7V). This is the normal connection for a 6V regulator and provides the highest efficiency. 3. EXTVCC connected to an external supply. If an external supply is available in the 5.5V to 7V range, it may be used to power EXTVCC provided it is compatible with the MOSFET gate drive requirements. Thermal Considerations and Output Current Derating In different applications, the LTM4605 operates in a variety of thermal environments. The maximum output current is limited by the environmental thermal condition. Sufficient cooling should be provided to ensure reliable operation. When the cooling is limited, proper output current de-rating is necessary, considering ambient temperature, airflow, input/ output condition, and the need for increased reliability. The power loss curves in Figures 5 and 6 can be used in coordination with the load current derating curves in Figures 7 to 12 for calculating an approximate θJA for the module. Column designation delineates between no heatsink, and a BGA heatsink. Each of the load current derating curves will lower the maximum load current as a function of the increased ambient temperature to keep the maximum junction temperature of the power module at 115°C maximum. This will allow a safe margin to work at the maximum operating temperature below 125°C. Each of the derating curves and the power loss curve that corresponds to the correct output voltage can be used to solve for the approximate θJA of the condition. A complete explanation of the thermal characteristics is provided in the thermal application note for the LTM4605. DESIGN EXAMPLES Buck Mode Operation As a design example, use input voltage VIN = 12V to 20V, VOUT = 12V and f = 400kHz. Set the PLLFLTR pin at 2.4V or more for 400kHz frequency and connect FCB to ground for continuous current mode operation. If a divider is used to set the frequency as shown in Figure 14, the bottom resistor R3 is recommended not to exceed 1k. 4605fa 13 LTM4605 APPLICATIONS INFORMATION To set the output voltage at 12V, the resistor RFB from VFB pin to ground should be chosen as: RFB = 0.8 V • 100k ≈ 7.15k VOUT − 0.8 V To choose a proper inductor, we need to know the current ripples at different input voltages. The inductor should be chosen by considering the worst case in the practical operating region. If the maximum output power P is 150W at buck mode, we can get the current ripple ratio of the current ripple ΔIL to the maximum inductor current IL as follows: ΔIL ( VIN – VOUT ) • VOUT 2 = IL VIN • L • f • P For the input capacitor, use a low ESR sized capacitor to handle the maximum RMS current. Input capacitors are required to be placed adjacent to the module. In Figure 14, the 10μF ceramic input capacitors are selected for their ability to handle the large RMS current into the converter. The 100μF bulk capacitor is only needed if the input source impedance is compromised by long inductive leads or traces. For the output capacitor, the output voltage ripple and transient requirements require low ESR capacitors. If assuming that the ESR dominates the output ripple, the output ripple is as follows: ΔVOUT(P-P) = ESR • ΔIL Figure 3 shows the current ripple ratio at different input voltages based on the inductor values: 1.5μH, 2.5μH, 3.3μH and 4.7μH. If we need 30% ripple current ratio at all inputs, the 3.3μH inductor can be selected. CURRENT RIPPLE RATIO Consider the safety margin about 30%, we can choose the sensing resistor as 8mΩ. If a total low ESR of about 5mΩ is chosen for output capacitors, the maximum output ripple of 17.5mV occurs at the input voltage of 20V with the current ripple at 3.5A. 0.8 Boost Mode Operation 0.6 For boost mode operation, use input voltage VIN = 5V to 12V, VOUT = 12V and f = 400kHz. 1.5μH Set the PLLFLTR pin and RFB as in buck mode. 0.4 2.5μH 3.3μH 0.2 4.7μH 0 12 16 18 14 INPUT VOLTAGE VIN (V) 20 4605 F03 Figure 3. Current Ripple Ratio at Different Inputs for Buck Mode At buck mode, sensing resistor selection is based on the maximum output current and the allowed maximum sensing threshold 130mV. RSENSE = If the maximum output power P is 60W at boost mode and the module efficiency η is about 95%, we can get the current ripple ratio of the current ripple ΔIL to the maximum inductor current IL as follows: ΔIL ( VOUT − VIN ) • VIN2 η = IL VOUT • L • f • P Figure 4. shows the current ripple ratio at different input voltages based on the inductor values: 1.5μH, 2.5μH, 3.3μH and 4.7μH. If we need 30% ripple current ratio at all inputs, the 3.3μH inductor can be selected. 2 • 130mV 2 • (P / VOUT ) − ΔIL 4605fa 14 LTM4605 APPLICATIONS INFORMATION output ripple is as follows: 0.6 ΔVOUT(P-P) = ESR • IL(MAX ) CURRENT RIPPLE RATIO 1.5μH 0.4 If a total low ESR about 5mΩ is chosen for output capacitors, the maximum output ripple of 70mV occurs at the input voltage of 5V with the peak inductor current at 14A. 2.5μH 3.3μH 0.2 4.7μH Wide Input Mode Operation 0 5 6 8 9 10 7 INPUT VOLTAGE VIN (V) 11 12 4605 F04 Figure 4. Current Ripple Ratio at Different Inputs for Boost Mode At boost mode, sensing resistor selection is based on the maximum input current and the allowed maximum sensing threshold 160mV. RSENSE = 2 • 160mV P 2• + ΔIL η • VIN(MIN) Consider the safety margin about 30%, we can choose the sensing resistor as 7mΩ. If a wide input range is required from 5V to 20V, the module will work in different operation modes. If input voltage VIN = 5V to 20V, VOUT = 12V and f = 400kHz, the design needs to consider the worst case in buck or boost mode design. Therefore, the maximum output power is limited to 60W. The sensing resistor is chosen at 7mΩ, the input capacitor is the same as the buck mode design and the output capacitor uses the boost mode design. Since the maximum output ripple normally occurs at boost mode in the wide input mode design, more inductor ripple current, up to 150% of the inductor current, is allowed at buck mode to meet the ripple design requirement. Thus, a 3.3μH inductor is chosen at the wide input mode. The maximum output ripple voltage is still 70mV if the total ESR is about 5mΩ. For the input capacitor, only minimum capacitors are needed to handle the maximum RMS current, since it is a continuous input current at boost mode. A 100μF capacitor is only needed if the input source impedance is compromised by long inductive leads or traces. Additionally, the current limit may become very high when the module runs at buck mode due to the low sensing resistor used in the wide input mode operation. Since the output capacitors at boost mode need to filter the square wave current, more capacitors are expected to achieve the same output ripples as the buck mode. If assuming that the ESR dominates the output ripple, the The LTM4605 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. Safety Considerations 4605fa 15 LTM4605 APPLICATIONS INFORMATION Table 3. Typical Components (f = 400kHz) COUT1 VENDORS PART NUMBER COUT2 VENDORS PART NUMBER TDK C4532X7R1E226M (22μF, 25V) Sanyo 16SVP180MX (180μF, 16V) INDUCTOR VENDORS PART NUMBER RSENSE VENDORS PART NUMBER Toko FDA1254 Vishay Power Metal Strip Resistors WSL1206-18 Sumida CDEP134, CDEP145 Panasonic Thick Film Chip Resistors ERJ12 VIN (V) VOUT (V) RSENSE (0.5W RATING) Inductor (μH) CIN (CERAMIC) CIN (BULK) COUT1 (CERAMIC) COUT2 (BULK) IOUT(MAX)* (A) 5 2.5 2x 16mΩ 0.5W 1 3x 10μF 25V 150μF 35V 2x 22μF 25V 1x 180μF 16V 12 12 2.5 2x 18mΩ 0.5W 1.5 2x 10μF 25V 150μF 35V 2x 22μF 25V 1x 180μF 16V 12 5 3.3 2x 18mΩ 0.5W 1 3x 10μF 25V 150μF 35V 2x 22μF 25V 1x 180μF 16V 12 12 3.3 2x 18mΩ 0.5W 1.5 2x 10μF 25V 150μF 35V 2x 22μF 25V 1x 180μF 16V 12 12 5 2x 18mΩ 0.5W 2.2 3x 10μF 25V 150μF 35V 2x 22μF 25V 1x 180μF 16V 12 20 5 2x 18mΩ 0.5W 2.5 2x 10μF 25V 150μF 35V 2x 22μF 25V 1x 180μF 16V 12 5 8 2x 14mΩ 0.5W 1.5 None 150μF 35V 4x 22μF 25V 2x 180μF 16V 8 12 8 2x 18mΩ 0.5W 2.2 3x 10μF 25V 150μF 35V 2x 22μF 25V 2x 180μF 16V 12 20 8 2x 18mΩ 0.5W 3.3 3x 10μF 25V 150μF 35V 2x 22μF 25V 2x 180μF 16V 12 5 10 2x 16mΩ 0.5W 2.2 None 150μF 35V 4x 22μF 25V 2x 180μF 16V 6 15 10 2x 18mΩ 0.5W 2.2 3x 10μF 25V 150μF 35V 2x 22μF 25V 2x 180μF 16V 12 20 10 2x 18mΩ 0.5W 3.3 3x 10μF 25V 150μF 35V 2x 22μF 25V 2x 180μF 16V 12 6 12 2x 14mΩ 0.5W 2.2 None 150μF 35V 4x 22μF 25V 2x 180μF 16V 6 16 12 2x 16mΩ 0.5W 2.2 2x 10μF 25V 150μF 35V 2x 22μF 25V 2x 180μF 16V 12 20 12 2x 18mΩ 0.5W 3.3 3x 10μF 25V 150μF 35V 2x 22μF 25V 2x 180μF 16V 12 5 16 2x 15mΩ 0.5W 3.3 None 150μF 35V 4x 22μF 25V 2x 150μF 20V 3.5 8 16 2x 14mΩ 0.5W 3.3 None 150μF 35V 4x 22μF 25V 2x 150μF 20V 6 12 16 2x 12mΩ 0.5W 2.2 None 150μF 35V 4x 22μF 25V 2x 150μF 20V 10 20 16 2x 18mΩ 0.5W 2.2 2x 10μF 25V 150μF 35V 2x 22μF 25V 2x 150μF 20V 12 INDUCTOR MANUFACTURER WEBSITE PHONE NUMBER Sumida www.sumida.com 408-321-9660 Toko www.toko.com 847-297-0070 SENSING RESISTOR MANUFACTURER WEBSITE PHONE NUMBER Panasonic www.panasonic.com/industrial/components 949-462-1816 KOA www.koaspeer.com 814-362-5536 Vishay www.vishay.com 800-433-5700 *Maximum load current is based on the Linear Technology Demo board DC1198A at room temperture with natural convection. Poor board layout design may decrease the maximum load current. 4605fa 16 LTM4605 TYPICAL APPLICATIONS 9 8 8 7 7 20VIN TO 12VOUT 6 5VIN TO 16VOUT POWER LOSS (W) POWER LOSS (W) Power loss includes all external components 6 5 4 3 5 4 3 2 2 5VIN TO 12VOUT 1 1 0 0 0 1 2 3 4 OUTPUT CURRENT (A) 0 5 2 4 6 8 OUTPUT CURRENT (A) 10 4605 F05 4605 F06 Figure 5. 5VIN Power Loss Figure 6. 20VIN Power Loss 5 MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) 5 4 3 2 1 5VIN TO 12VOUT WITH 0LFM 5VIN TO 12VOUT WITH 200LFM 5VIN TO 12VOUT WITH 400LFM 0 25 35 4 3 2 1 5VIN TO 12VOUT WITH 0LFM 5VIN TO 12VOUT WITH 200LFM 5VIN TO 12VOUT WITH 400LFM 0 45 55 65 75 85 95 105 115 AMBIENT TEMPERATURE (°C) 25 45 65 85 105 AMBIENT TEMPERATURE (°C) 4605 F07 Figure 8. 5VIN to 12VOUT with Heatsink 4.0 3.5 3.5 MAXIMUM LOAD CURRENT (A) 4.0 3.0 2.5 2.0 1.5 1.0 5VIN TO 16VOUT WITH 0LFM 5VIN TO 16VOUT WITH 200LFM 5VIN TO 16VOUT WITH 400LFM 0.5 0 25 35 3.0 2.5 2.0 1.5 1.0 5VIN TO 16VOUT WITH 0LFM 5VIN TO 16VOUT WITH 200LFM 5VIN TO 16VOUT WITH 400LFM 0.5 0 45 55 65 75 85 95 AMBIENT TEMPERATURE (°C) 105 4605 F09 Figure 9. 5VIN to 16VOUT without Heatsink 125 4605 F08 Figure 7. 5VIN to 12VOUT without Heatsink MAXIMUM LOAD CURRENT (A) 12 25 35 45 55 65 75 85 95 AMBIENT TEMPERATURE (°C) 105 4605 F10 Figure 10. 5VIN to 16VOUT with Heatsink 4605fa 17 LTM4605 TYPICAL APPLICATIONS Power loss includes all external components BGA Heat Sink 12 12 10 10 MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) No Heat Sink 8 6 4 2 0 8 6 4 2 0 35 45 55 65 75 85 95 AMBIENT TEMPERATURE (°C) 20VIN TO 12VOUT WITH 0LFM 20VIN TO 12VOUT WITH 200LFM 20VIN TO 12VOUT WITH 400LFM 105 4605 F11 Figure 11. 20VIN to 12VOUT without Heatsink 35 45 55 65 75 85 95 AMBIENT TEMPERATURE (°C) 20VIN TO 12VOUT WITH 0LFM 20VIN TO 12VOUT WITH 200LFM 20VIN TO 12VOUT WITH 400LFM 105 4605 F12 Figure 12. 20VIN to 12VOUT with Heatsink 4605fa 18 LTM4605 APPLICATIONS INFORMATION Table 4. 5V Output DERATING CURVE VIN (V) POWER LOSS CURVE AIR FLOW (LFM) HEATSINK θJA (°C/W)* Figure 7, 9 12, 16 Figure 5 0 none 11.2 Figure 7, 9 12, 16 Figure 5 200 none 8.3 Figure 7, 9 12, 16 Figure 5 400 none 7.2 Figure 8, 10 12, 16 Figure 5 0 BGA Heatsink 10.7 Figure 8, 10 12, 16 Figure 5 200 BGA Heatsink 7.7 Figure 8, 10 12, 16 Figure 5 400 BGA Heatsink 6.6 VIN (V) POWER LOSS CURVE AIR FLOW (LFM) HEATSINK θJA (°C/W)* Figure 11 20 Figure 6 0 none 8.2 Figure 11 20 Figure 6 200 none 5.8 Figure 11 20 Figure 6 400 none 5.3 Figure 12 20 Figure 6 0 BGA Heatsink 7.6 Figure 12 20 Figure 6 200 BGA Heatsink 5.3 Figure 12 20 Figure 6 400 BGA Heatsink 4.8 Table 5. 20V Input and 12V Output DERATING CURVE HEATSINK MANUFACTURER PART NUMBER PHONE NUMBER Wakefield Engineering LTN20069 603-635-2600 *The results of thermal resistance from junction to ambient θJA are based on the demo board of DC1198A. Thus, the maximum temperature on board is treated as the junction temperature (which is in the μModule for most cases) and the power losses from all components are counted for calculations. It has to be mentioned that poor board design may increase the θJA. 4605fa 19 LTM4605 APPLICATIONS INFORMATION Layout Checklist/Example • Use a separated SGND ground copper area for components connected to signal pins. Connect the SGND to PGND underneath the unit. The high integration of LTM4605 makes the PCB board layout very simple and easy. However, to optimize its electrical and thermal performance, some layout considerations are still necessary. Figure 13. gives a good example of the recommended layout. • Use large PCB copper areas for high current path, including VIN, RSENSE, SW1, SW2, PGND and VOUT. It helps to minimize the PCB conduction loss and thermal stress. SW1 SW2 VIN L1 • Place high frequency input and output ceramic capacitors next to the VIN, PGND and VOUT pins to minimize high frequency noise • Route SENSE– and SENSE+ leads together with minimum PC trace spacing. Avoid sense lines passing through noisy areas, such as switch nodes. RSENSE VOUT • Place a dedicated power ground layer underneath the unit. CIN COUT • To minimize the via conduction loss and reduce module thermal stress, use multiple vias for interconnection between the top layer and other power layers + – SGND PGND PGND RSENSE • Do not put vias directly on pads, unless the vias are capped. 4605 F13 KELVIN CONNECTIONS TO RSENSE Figure 13. Recommended PCB Layout TYPICAL APPLICATIONS VIN 12V TO 20V CLOCK SYNC 10μF 35V x2 PGOOD VIN ON/OFF RUN COMP PLLIN V OUT FCB LTM4605 INTVCC R1 1.5k R3 1k L1 3.3μH 100μF 25V VOUT 12V 12A SW1 SW2 PLLFLTR C3 0.1μF + EXTVCC RSENSE STBYMD SENSE+ SS SENSE– R2 8mΩ SGND PGND VFB RFB 7.15k 4605 TA02 Figure 14. Buck Mode Operation with 12V to 20V Input 4605fa 20 LTM4605 TYPICAL APPLICATIONS VIN 4.5V TO 12V CLOCK SYNC 4.7μF 35V PGOOD VIN ON/OFF RUN COMP R1 1.5k R3 1k C3 0.1μF PLLIN V OUT FCB LTM4605 2Ω INTVCC SW1 PLLFLTR SW2 EXTVCC RSENSE STBYMD SENSE+ SS SENSE– L1 3.3μH 22μF 25V x2 2200pF + 330μF 25V VOUT 12V 5A OPTIONAL FOR LOW SWITCHING NOISE R2 7mΩ SGND VFB PGND RFB 7.15k 4605 TA03 Figure 15. Boost Mode Operation with 4.5V to 12V Input VIN 4.5V TO 20V CLOCK SYNC 10μF 35V x2 PGOOD VIN ON/OFF PLLIN V OUT RUN COMP FCB LTM4605 R3 1k SW2 PLLFLTR C3 0.1μF 330μF 25V VOUT 12V 5A SW1 INTVCC R1 1.5k 22μF 25V x2 L1 3.3μH + EXTVCC RSENSE STBYMD SENSE+ R2 7mΩ SENSE– SS SGND PGND VFB RFB 7.15k 4605 TA04 Figure 16. Wide Input Mode with 4.5V to 20V Input, 12V at 5A Output 4605fa 21 LTM4605 TYPICAL APPLICATIONS VIN 4.5V TO 20V CLOCK SYNC 10μF 35V x2 ON/OFF PGOOD VIN PLLIN V OUT RUN COMP + FCB L1 2.5μH LTM4605 INTVCC SW1 R1 1.5k PLLFLTR SW2 EXTVCC RSENSE C3 R3 1k 0.1μF STBYMD SENSE+ SS SENSE– 100μF 25V 2Ω VOUT 5V 12A 2200pF OPTIONAL R2 8mΩ SGND VFB PGND RFB 19k 4605 TA05 Figure 17. 5V at 12A Design with Low Switching Noise (Optional) VIN 4.5V TO 20V CLOCK SYNC 0° PHASE 10μF 35V R5 100k PGOOD VIN PLLIN V OUT RUN FCB LTM4605 COMP R4 324k LTC6908-1 V+ OUT1 GND OUT2 SET 5.1V RSENSE EXTVCC SENSE+ 330μF 25V R2 7mΩ SENSE– SS C3 0.1μF SGND + SW2 PLLFLTR STBYMD MOD C2 22μF x2 SW1 INTVCC C1 0.1μF L1 3.3μH VOUT 12V 10A PGND VFB RFB 3.57k 2-PHASE OSCILLATOR CLOCK SYNC 180° PHASE 10μF 35V PGOOD VIN PLLIN V OUT FCB RUN LTM4605 COMP L2 3.3μH + 330μF 25V SW1 INTVCC SW2 PLLFLTR RSENSE EXTVCC SENSE+ R3 7mΩ STBYMD SENSE– SS SGND C4 22μF x2 PGND VFB 4605 TA06 Figure 18. Two-Phase Parallel, 12V at 10A Design 4605fa 22 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. 6.9850 5.7150 4.4450 3.1750 1.9050 0.6350 0.0000 0.6350 1.9050 3.1750 4.4450 5.7150 6.9850 PACKAGE TOP VIEW 3.1750 3.1750 SUGGESTED PCB LAYOUT TOP VIEW 1.9050 4 0.6350 0.0000 0.6350 PAD 1 CORNER 15 BSC 1.9050 aaa Z 6.9850 5.7150 4.4450 4.4450 5.7150 6.9850 X 15 BSC Y bbb Z DETAIL B 2.72 – 2.92 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 MARKED FEATURE LAND DESIGNATION PER JESD MO-222, SPP-010 SYMBOL TOLERANCE 0.10 aaa 0.10 bbb 0.05 eee 6. THE TOTAL NUMBER OF PADS: 141 5. PRIMARY DATUM -Z- IS SEATING PLANE 4 3 2. ALL DIMENSIONS ARE IN MILLIMETERS 3 12 11 TRAY PIN 1 BEVEL COMPONENT PIN “A1” PADS SEE NOTES 1.27 BSC 13.97 BSC 0.12 – 0.28 NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 DETAIL A 0.27 – 0.37 SUBSTRATE eee S X Y DETAIL B 0.630 ±0.025 SQ. 141x aaa Z 2.45 – 2.55 MOLD CAP Z (Reference LTC DWG # 05-08-1815 Rev A) LGA Package 141-Lead (15mm × 15mm × 2.82mm) 10 7 6 5 LTMXXXXXX μModule PACKAGE BOTTOM VIEW 8 4 3 2 LGA 141 1007 REV A 1 DETAIL A PACKAGE IN TRAY LOADING ORIENTATION 9 13.97 BSC A B C D E F G H J K L M PAD 1 LTM4605 PACKAGE DESCRIPTION 4605fa 23 LTM4605 PACKAGE DESCRIPTION Pin Assignment Table 6 (Arranged by Pin Number) PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME A1 PGND C1 PGND E1 VOUT G1 VOUT J1 SW1 L1 SW1 A2 PGND C2 PGND E2 VOUT G2 VOUT J2 SW1 L2 SW1 A3 PGND C3 PGND E3 PGND G3 VOUT J3 SW1 L3 SW1 A4 SENSE+ C4 PGND E4 PGND G4 VOUT J4 SW1 L4 SW1 A5 SENSE– C5 PGND E5 PGND G5 RSENSE J5 RSENSE L5 RSENSE A6 SS C6 PGND E6 PGND G6 RSENSE J6 RSENSE L6 RSENSE A7 SGND C7 PGND E7 PGND G7 RSENSE J7 RSENSE L7 SW2 A8 RUN C8 PGND E8 PGND G8 RSENSE J8 SW2 L8 SW2 A9 FCB C9 PGND E9 PGND G9 RSENSE J9 SW2 L9 SW2 A10 STBYMD C10 PGND E10 PGND G10 RSENSE J10 VIN L10 VIN A11 PGND C11 PGND E11 PGND G11 RSENSE J11 VIN L11 VIN A12 PGND C12 PGND E12 PGND G12 RSENSE J12 VIN B1 PGND D1 PGND F1 VOUT H1 VOUT K1 SW1 M1 B2 PGND D2 PGND F2 VOUT H2 VOUT K2 SW1 M2 SW1 B3 PGND D3 PGND F3 VOUT H3 VOUT K3 SW1 M3 SW1 B4 PGND D4 PGND F4 VOUT H4 VOUT K4 SW1 M4 SW1 RSENSE L12 VIN SW1 B5 PGOOD D5 PGND F5 INTVCC H5 RSENSE K5 RSENSE M5 B6 VFB D6 PGND F6 EXTVCC H6 RSENSE K6 RSENSE M6 RSENSE B7 COMP D7 PGND F7 – H7 RSENSE K7 SW2 M7 SW2 B8 PLLFLTR D8 PGND F8 – H8 RSENSE K8 SW2 M8 SW2 B9 PLLIN PGND F9 – H9 RSENSE K9 SW2 M9 SW2 D9 B10 PGND D10 PGND F10 RSENSE H10 RSENSE K10 VIN B11 PGND D11 PGND F11 RSENSE H11 RSENSE K11 VIN M10 VIN M11 VIN B12 PGND D12 PGND F12 RSENSE H12 RSENSE K12 VIN M12 VIN 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 LTC3780 36V Buck-Boost Controller Synchronous Operation, Single Inductor LTC3785 10V Buck-Boost Controller Synchronous Operation, No RSENSE™, 2.7V ≤ VIN ≤ 10V, 2.7V ≤ VOUT ≤ 10V 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 LTM4601/ LTM4601A 12A DC/DC μModule with PLL, Output Tracking/ Margining and Remote Sensing Synchronizable, PolyPhase Operation to 48A, LTM4601-1 Version has no Remote Sensing LTM4602 6A DC/DC μModule Pin Compatible with the LTM4600 LTM4603 6A DC/DC μModule with PLL and Output Tracking/ Margining and Remote Sensing Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote Sensing, Pin Compatible with the LTM4601 LTM4604 4A Low Voltage DC/DC μModule 2.375 ≤ VIN ≤ 5V, 0.8V ≤ VOUT ≤ 5V, 9mm × 15mm × 2.3mm Package No RSENSE is a Trademark of Linear Technology Corporation. 4605fa 24 Linear Technology Corporation LT 0108 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2007