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LTM4605 High Efficiency Buck-Boost DC/DC Module DESCRIPTION
The LTM(R)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. 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. Fault protection features include overvoltage and foldback current protection. The DC/DC ModuleTM is offered in a small and thermally enhanced 15mm x 15mm x 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. Module is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
FEATURES
n 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 x 15mm x 2.8mm)
APPLICATIONS
n n n
Telecom, Servers and Networking Equipment Industrial and Automotive Equipment High Power Battery-Operated Devices
TYPICAL APPLICATION
12V/5A Buck-Boost DC/DC Module with 4.5V to 20V Input
VIN 4.5V TO 20V CLOCK SYNC 10F 35V ON/OFF VIN RUN PLLIN V OUT FCB LTM4605 SW1 SW2 RSENSE SENSE+ 0.1F SS SGND PGND SENSE- VFB 7.15k
4605 TA01
Efficiency and Power Loss vs Input Voltage
99 VOUT 12V 5A EFFICIENCY (%) 98 97 96 95 4 94 93 92 91 90 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 VIN (V)
4605 TA01b
10F 35V 4.7H
+
VOUT = 12V ILOAD = 5A f = 200kHz
8 7 6 POWER LOSS (W) 5
330F 25V
3 2 1 0
6m
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LTM4605 PIN CONFIGURATION
(See Table 6. Pin Assignment)
TOP VIEW BANK 2
M L
ABSOLUTE MAXIMUM RATINGS
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) ...............................................-40C to 85C Junction Temperature ........................................... 125C Storage Temperature Range...................-55C to 125C
BANK 4
K J H G
BANK 1
BANK 3
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 15mm
2.8mm)
TJMAX = 125C, JP = 4C/W WEIGHT = 1.5g
ORDER INFORMATION
LEAD FREE FINISH LTM4605EV#PBF LTM4605IV#PBF PART MARKING* LTM4605V LTM4605V PACKAGE DESCRIPTION 141-Lead (15mm x 15mm x 2.8mm) LGA 141-Lead (15mm x 15mm x 2.8mm) LGA TEMPERATURE RANGE -40C to 85C -40C to 85C
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
SYMBOL Input Specifications VIN(DC) VIN(UVLO) IQ(VIN) Input DC Voltage Undervoltage Lockout Threshold Input Supply Bias Current Normal Standby Shutdown Supply Current PARAMETER
The l denotes the specifications which apply over the -40C to 85C temperature range, otherwise specifications are at TA = 25C, VIN = 12V. Per typical application (front page) configuration.
CONDITIONS
l
MIN 4.5
TYP
MAX 20
UNITS V V mA mA A
VIN Falling
l
3.4 2.8 1.6 35
4
VRUN = 0V, VSTBYMD > 2V VRUN = 0V, VSTBYMD = Open
60
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ELECTRICAL CHARACTERISTICS
SYMBOL IOUTDC PARAMETER Output Specifications
The l denotes the specifications which apply over the -40C to 85C temperature range, otherwise specifications are at TA = 25C, VIN = 12V. Per typical application (front page) configuration.
CONDITIONS MIN TYP 12 5 0.002
l l
MAX
UNITS A A
Output Continuous Current Range VIN = 12V, VOUT = 5V (See Output Current Derating Curves VIN = 6V, VOUT = 12V for Different VIN, VOUT and TA) Reference Voltage Line Regulation Accuracy Load Regulation Accuracy VIN = 4.5V to 20V, VCOMP = 1.2V (Note 3) VCOMP = 1.2V to 0.7V VCOMP = 1.2V to 1.8V (Note 3) Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Drain to Source Voltage VDS = 12V, Bias Current ISW = 10mA Bias Current ISW = 3A Bias Current ISW = 3A Bias Current ISW = 3A Bias Current ISW = 3A
VFB/VFB(NOM) VFB/VFB(LOAD) Switch Section M1 tr M1 tf M3 tr M3 tf M2, M4 tr M2, M4 tf t1d t2d t3d t4d Mode Transition 1 Mode Transition 2 M1 RDS(ON) M2 RDS(ON) M3 RDS(ON) M4 RDS(ON)
0.02 0.5 -0.5
% % % ns ns ns ns ns ns ns ns ns ns ns ns m
0.15 -0.15 50 40 25 20 20 20 50 50 50 50 220 220 6.5 8 8 8
Turn-On Time (Note 4) Turn-Off Time Turn-On Time Turn-Off Time Turn-On Time Turn-Off Time M1 Off to M2 On Delay (Note 4) M2 Off to M1 On Delay M3 Off to M4 On Delay M4 Off to M3 On Delay M2 Off to M4 On Delay M4 Off to M2 On Delay Static Drain-to-Source OnResistance Static Drain-to-Source OnResistance Static Drain-to-Source OnResistance Static Drain-to-Source OnResistance Nominal Frequency Lowest Frequency Highest Frequency PLLIN Input Resistance Phase Detector Output Current
12 12 12
m m m
Oscillator and Phase-Locked Loop fNOM fLOW fHIGH RPLLIN IPLLFLTR VPLLFLTR = 1.2V VPLLFLTR = 0V VPLLFLTR = 2.4V fPLLIN < fOSC fPLLIN > fOSC 260 170 340 300 200 400 50 -15 15 330 220 440 kHz kHz kHz k A A
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The l denotes the specifications which apply over the -40C to 85C temperature range, otherwise specifications are at TA = 25C, VIN = 12V. Per typical application (front page) configuration.
SYMBOL Control Section VFB VRUN ISS VSTBYMD(START) VSTBYMD(KA) VFCB IFCB VBURST DF(BOOST, MAX) DF(BUCK, MAX) tON(MIN, BUCK) RFBHI INTVCC VLDO/VLDO VEXTVCC VEXTVCC(HYS) VEXTVCC VSENSE(MAX) VSENSE(MIN, BUCK) ISENSE PGOOD VFBH VFBL VFB(HYS) VPGL IPGOOD PGOOD Upper Threshold PGOOD Lower Threshold PGOOD Hysteresis PGOOD Low Voltage PGOOD Leakage Current VFB Rising VFB Falling VFB Returning IPGOOD = 2mA VPGOOD = 5V 5.5 -5.5 7.5 -7.5 2.5 0.2 0.3 1 10 -10 % % % V A Feedback Reference Voltage RUN Pin ON/OFF Threshold Soft-Start Charging Current Start-Up Threshold Keep-Active Power On Threshold Forced Continuous Threshold Forced Continuous Pin Current Burst Inhibit (Constant Frequency) Threshold Maximum Duty Factor Maximum Duty Factor VFCB = 0.85V Measured at FCB Pin % Switch M4 On % Switch M1 On VRUN = 2.2V VSTBYMD Rising VSTBYMD Rising, VRUN = 0V 0.76 -0.3 VCOMP = 1.2V
l
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN 0.792 1 1 0.4
TYP 0.8 1.6 1.7 0.7 1.25 0.8 -0.2 5.3 99 99 200
MAX 0.808 2.2
UNITS V V A V V
0.84 -0.1 5.5
V A V % %
Minimum On-Time for Synchronous Switch M1 (Note 5) Switch in Buck Operation Resistor Between VOUT and VFB pins Internal VCC Voltage Internal VCC Load Regulation EXTVCC Switchover Voltage EXTVCC Switchover Hysteresis EXTVCC Switch Drop Voltage Maximum Current Sense Threshold Minimum Current Sense Threshold Sense Pins Total Source Current ICC = 20mA, VEXTVCC = 6V Boost Mode Buck Mode Discontinuous Mode VSENSE- = VSENSE+ = 0V
l l
250 100.5 6.3 2
ns k V % V mV
99.5 VIN > 7V, VEXTVCC = 5V ICC = 0mA to 20mA, VEXTVCC = 5V ICC = 20mA, VEXTVCC Rising
l l
100 6 0.3 5.6 300 60 160 -130 -6 -380
Internal VCC Regulator 5.7 5.4
150 190 -150
mV mV mV mV A
Current Sensing Section -95
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 0C to 85C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation
with statistical process controls. The LTM4605I is guaranteed over the -40C to 85C 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.
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(Refer to Figure 16) Efficiency vs Load Current 18VIN to 12VOUT
95 85 75 EFFICIENCY (%) 65 55 45 35 CCM DCM BURST 0.1 1 LOAD CURRENT (A) 10
4605 G02
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current 6VIN to 12VOUT
100 90 80 EFFICIENCY (%) EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.01 0.1 1 LOAD CURRENT (A) CCM DCM BURST 10
4605 G01
Efficiency vs Load Current 12VIN to 12VOUT
100 90 80 70 60 50 40 30 20 10 0 0.01
25 15 0.01
CCM DCM SKIP CYCLE 0.1 1 10 LOAD CURRENT (A) 100
4605 G03
Efficiency vs Load Current 3.3H Inductor (CCM)
100 95 90 EFFICIENCY (%) EFFICIENCY (%) 85 80 75 70 65 60 0 3 18VIN TO 5VOUT 12VIN TO 5VOUT 5VIN TO 5VOUT 6 9 LOAD CURRENT (A) 12
4605 G04
Efficiency vs Load Current 1.5H Inductor (CCM)
100 95 90 EFFICIENCY (%) 18VIN TO 3.3VOUT 12VIN TO 3.3VOUT 5VIN TO 3.3VOUT 0 3 6 9 LOAD CURRENT (A) 12
4605 G05
Efficiency vs Load Current 1.5H Inductor (CCM)
100 95 90 85 80 75 70 65 60 55 50 0 3 18VIN TO 2.5VOUT 12VIN TO 2.5VOUT 5VIN TO 2.5VOUT 6 9 LOAD CURRENT (A) 12
4605 G06
85 80 75 70 65 60 55 50
Transient Response from 6VIN to 12VOUT
IOUT 2A/DIV IOUT 2A/DIV
Transient Response from 12VIN to 12VOUT
IOUT 2A/DIV
Transient Response from 18VIN to 12VOUT
VOUT 200mV/DIV 200s/DIV
4605 G07
VOUT 200mV/DIV 200s/DIV
4605 G08
VOUT 100mV/DIV 200s/DIV
4605 G09
LOAD STEP: 0A TO 3A AT CCM OUTPUT CAPS: 4x 22F CERAMIC CAPS AND 2x 180F ELECTROLYTIC CAPS 2x 15m SENSING RESISTORS
LOAD STEP: 0A TO 3A AT CCM OUTPUT CAPS: 4x 22F CERAMIC CAPS AND 2x 180F ELECTROLYTIC CAPS 2x 15m SENSING RESISTORS
LOAD STEP: 0A TO 4A AT CCM OUTPUT CAPS: 4x 22F CERAMIC CAPS AND 2x 180F ELECTROLYTIC CAPS 2x 15m SENSING RESISTORS
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LTM4605 TYPICAL PERFORMANCE CHARACTERISTICS
Start-Up with 6VIN to 12VOUT at IOUT = 5A
VOUT 5V/DIV IIN 5A/DIV IL 5A/DIV 50ms/DIV
4605 G10
Start-Up with 18VIN to 12VOUT at IOUT = 5A
VOUT 5V/DIV IIN 2A/DIV IL 5A/DIV 50ms/DIV
4605 G11
0.22F SOFT-START CAP OUTPUT CAPS: 4x 22F CERAMIC CAPS AND 2x 180F ELECTROLYTIC CAPS 2x 15m SENSING RESISTORS
0.22F SOFT-START CAP OUTPUT CAPS: 4x 22F CERAMIC CAPS AND 2x 180F ELECTROLYTIC CAPS 2x 15m SENSING RESISTORS
Short Circuit with 6VIN to 12VOUT at IOUT = 5A
VOUT 5V/DIV VOUT 10V/DIV IIN 5A/DIV
Short Circuit with 18VIN to 12VOUT at IOUT = 5A
IIN 10A/DIV
20s/DIV
4605 G12
100s/DIV
4605 G13
OUTPUT CAPS: 4x 22F CERAMIC CAPS AND 2x 180F ELECTROLYTIC CAPS 2x 15m SENSING RESISTORS
OUTPUT CAPS: 4x 22F CERAMIC CAPS AND 2x 180F ELECTROLYTIC CAPS 2x 15m SENSING RESISTORS
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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 25s 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.
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. SS (Pin A6): Soft-Start Pin. Soft-start reduces the input power sources' surge currents by gradually increasing the controller's current limit.
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SIMPLIFIED BLOCK DIAGRAM
VIN 4.5V TO 20V EXTVCC M1 INTVCC PGOOD M2 L SW1 VOUT 12V 5A CO1 M3 0.1F COMP M4 INT COMP SS SS 0.1F PLLIN INT FILTER PLLFLTR SENSE- RSENSE CONTROLLER RSENSE SENSE+ 100k VFB COUT RFB 7.15k SW2 C1 CIN
RUN ON/OFF 100k STBYMD
INT FILTER FCB SGND TO PGND PLANE AS SHOWN IN FIGURE 13 1000pF
PGND
4605 BD
Figure 1. Simplified LTM4605 Block Diagram
DECOUPLING REQUIREMENTS TA = 25C. Use Figure 1 configuration.
SYMBOL CIN COUT PARAMETER External Input Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 12V) External Output Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 12V) CONDITIONS IOUT = 5A IOUT = 5A MIN 10 200 300 TYP MAX UNITS F F
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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.
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
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. Output Voltage Programming The PWM controller has an internal 0.8V1% 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.
Table 1. RFB Resistor (0.5%) vs Various Output Voltages
VOUT RFB VOUT RFB 0.8V Open 8V 11k 1.5V 115k 9V 9.76k 2.5V 47.5k 10V 8.66k 3.3V 32.4k 12V 7.15k 5V 19k 15V 5.62k 6V 15.4k 16V 5.23k
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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.
450 400 OPERATING FREQUENCY (kHz) 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
APPLICATIONS INFORMATION
by accepting a logic input on the FCB pin. Table 2 shows the different operation modes.
Table 2. Different Operating Modes
FCB PIN 0V to 0.75V 0.85V to 5V >5.3V BUCK Force Continuous Mode Skip-Cycle Mode DCM with Constant Freq BOOST Force Continuous Mode Burst Mode Operation DCM with Constant Freq
Figure 2. Frequency vs PLLFLTR Pin Voltage
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.
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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
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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 300F 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. Inductor Selection The inductor is chiefly decided by the required ripple current and the operating frequency. The inductor current ripple IL 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 VIN * VOUT(MAX ) - VIN
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 ) * D * (1- D)
In the above equation, 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 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 = IOUT(MAX ) * VOUT - VIN(MIN) COUT * VOUT * f VOUT * VIN(MAX ) - VOUT
(
)
VOUT(MAX ) * f * IOUT(MAX ) * Ripple% M VOUT * VIN(MAX ) - VOUT
LBUCK where:
(
)
VIN(MAX ) * f * IOUT(MAX ) * Ripple%
(
)
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.
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VRIPPLE,BUCK =
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 = IL(MAX ) * ESR VESR,BOOST = IL(MAX ) * ESR
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RSENSE Selection and Maximum Output Current the internal reference and the output voltage. The total soft-start time can be calculated as: t SOFTSTART = 2.4V * CSS 1.7A
APPLICATIONS INFORMATION
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 IL VIN IOUT(MAX,BOOST) = - * 2 VOUT RSENSE where IL is peak-to-peak inductor ripple current. In buck mode, the allowed maximum average load current is: IOUT(MAX,BUCK ) = 130mV IL + RSENSE 2
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 = Power Good 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. 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
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The maximum current sensing RSENSE value for the boost mode is: RSENSE(MAX,BOOST) = 2 * 160mV * VIN 2 * IOUT(MAX,BOOST) * VOUT + IL * VIN The maximum current sensing RSENSE value for the buck mode is: RSENSE(MAX,BUCK ) = 2 * 130mV 2 * IOUT(MAX,BUCK ) - IL
R + 100k * 1.6 V 100k
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 1.7A current source will charge up the external soft-start capacitor. This will control the ramp of
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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 JA 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 115C maximum. This will allow a safe margin to work at the maximum operating temperature below 125C. 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 JA 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.
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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.
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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 Consider the safety margin about 30%, we can choose the sensing resistor as 8m. 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 10F ceramic input capacitors are selected for their ability to handle the large RMS current into the converter. The 100F 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: VOUT(P-P) = ESR * IL If a total low ESR of about 5m 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. Boost Mode Operation For boost mode operation, use input voltage VIN = 5V to 12V, VOUT = 12V and f = 400kHz. Set the PLLFLTR pin and RFB as in buck mode.
2.5H 0.2 3.3H 4.7H
APPLICATIONS INFORMATION
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 IL to the maximum inductor current IL as follows: IL ( VIN - VOUT ) * VOUT 2 = IL VIN * L * f * P Figure 3 shows the current ripple ratio at different input voltages based on the inductor values: 1.5H, 2.5H, 3.3H and 4.7H. If we need 30% ripple current ratio at all inputs, the 3.3H inductor can be selected.
0.8
CURRENT RIPPLE RATIO
0.6 1.5H 0.4
If the maximum output power P is 60W at boost mode and the module efficiency is about 95%, we can get the current ripple ratio of the current ripple IL to the maximum inductor current IL as follows: IL ( VOUT - VIN ) * VIN2 = IL VOUT * L * f * P Figure 4. shows the current ripple ratio at different input voltages based on the inductor values: 1.5H, 2.5H, 3.3H and 4.7H. If we need 30% ripple current ratio at all inputs, the 3.3H inductor can be selected.
0 12 16 18 14 INPUT VOLTAGE VIN (V) 20
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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 = 2 * 130mV 2 * (P / VOUT ) - IL
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output ripple is as follows:
APPLICATIONS INFORMATION
0.6 1.5H CURRENT RIPPLE RATIO
VOUT(P-P) = ESR * IL(MAX ) If a total low ESR about 5m 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. Wide Input Mode Operation
11 12
0.4 2.5H 3.3H 0.2 4.7H
0 5 6 8 9 10 7 INPUT VOLTAGE VIN (V)
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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* + IL * VIN(MIN)
Consider the safety margin about 30%, we can choose the sensing resistor as 7m. 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 100F capacitor is only needed if the input source impedance is compromised by long inductive leads or traces. 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
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 7m, 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 3.3H inductor is chosen at the wide input mode. The maximum output ripple voltage is still 70mV if the total ESR is about 5m. 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. Safety Considerations 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.
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Table 3. Typical Components (f = 400kHz)
COUT1 VENDORS TDK INDUCTOR VENDORS Toko Sumida PART NUMBER C4532X7R1E226M (22F 25V) , PART NUMBER FDA1254 CDEP134, CDEP145 COUT2 VENDORS Sanyo RSENSE VENDORS Vishay Panasonic PART NUMBER 16SVP180MX (180F 16V) , PART NUMBER Power Metal Strip Resistors WSL1206-18 Thick Film Chip Resistors ERJ12
APPLICATIONS INFORMATION
VIN (V) 5 12 5 12 12 20 5 12 20 5 15 20 6 16 20 5 8 12 20
VOUT (V) 2.5 2.5 3.3 3.3 5 5 8 8 8 10 10 10 12 12 12 16 16 16 16
RSENSE (0.5W RATING) 2x 16m 0.5W 2x 18m 0.5W 2x 18m 0.5W 2x 18m 0.5W 2x 18m 0.5W 2x 18m 0.5W 2x 14m 0.5W 2x 18m 0.5W 2x 18m 0.5W 2x 16m 0.5W 2x 18m 0.5W 2x 18m 0.5W 2x 14m 0.5W 2x 16m 0.5W 2x 18m 0.5W 2x 15m 0.5W 2x 14m 0.5W 2x 12m 0.5W 2x 18m 0.5W
Inductor (H) 1 1.5 1 1.5 2.2 2.5 1.5 2.2 3.3 2.2 2.2 3.3 2.2 2.2 3.3 3.3 3.3 2.2 2.2
CIN (CERAMIC) 3x 10F 25V 2x 10F 25V 3x 10F 25V 2x 10F 25V 3x 10F 25V 2x 10F 25V None 3x 10F 25V 3x 10F 25V None 3x 10F 25V 3x 10F 25V None 2x 10F 25V 3x 10F 25V None None None 2x 10F 25V
CIN (BULK) 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V
COUT1 (CERAMIC) 2x 22F 25V 2x 22F 25V 2x 22F 25V 2x 22F 25V 2x 22F 25V 2x 22F 25V 4x 22F 25V 2x 22F 25V 2x 22F 25V 4x 22F 25V 2x 22F 25V 2x 22F 25V 4x 22F 25V 2x 22F 25V 2x 22F 25V 4x 22F 25V 4x 22F 25V 4x 22F 25V 2x 22F 25V
COUT2 (BULK) 1x 180F 16V 1x 180F 16V 1x 180F 16V 1x 180F 16V 1x 180F 16V 1x 180F 16V 2x 180F 16V 2x 180F 16V 2x 180F 16V 2x 180F 16V 2x 180F 16V 2x 180F 16V 2x 180F 16V 2x 180F 16V 2x 180F 16V 2x 150F 20V 2x 150F 20V 2x 150F 20V 2x 150F 20V
IOUT(MAX)* (A) 12 12 12 12 12 12 8 12 12 6 12 12 6 12 12 3.5 6 10 12
INDUCTOR MANUFACTURER Sumida Toko
WEBSITE www.sumida.com www.toko.com
PHONE NUMBER 408-321-9660 847-297-0070
SENSING RESISTOR MANUFACTURER Panasonic KOA Vishay
WEBSITE www.panasonic.com/industrial/components www.koaspeer.com www.vishay.com
PHONE NUMBER 949-462-1816 814-362-5536 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.
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Power loss includes all external components
8 7 5VIN TO 16VOUT 6 POWER LOSS (W) 5
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TYPICAL APPLICATIONS
9 8 7 POWER LOSS (W) 6 5 4 3 2 1 0 0 1 2 3 4 OUTPUT CURRENT (A)
20VIN TO 12VOUT
5 4 3 2
5VIN TO 12VOUT
1 0 0 2 4 6 8 OUTPUT CURRENT (A) 10 12
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Figure 5. 5VIN Power Loss
Figure 6. 20VIN Power Loss
5
5
MAXIMUM LOAD CURRENT (A)
4
MAXIMUM LOAD CURRENT (A)
4
3
3
2
2
1
0 25 35
5VIN TO 12VOUT WITH 0LFM 5VIN TO 12VOUT WITH 200LFM 5VIN TO 12VOUT WITH 400LFM 45 55 65 75 85 95 105 115 AMBIENT TEMPERATURE (C)
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1
0 25
5VIN TO 12VOUT WITH 0LFM 5VIN TO 12VOUT WITH 200LFM 5VIN TO 12VOUT WITH 400LFM 45 65 85 105 AMBIENT TEMPERATURE (C) 125
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Figure 7. 5VIN to 12VOUT without Heatsink
Figure 8. 5VIN to 12VOUT with Heatsink
4.0 3.5 MAXIMUM LOAD CURRENT (A) 3.0 2.5 2.0 1.5 1.0 0.5 0 25 35 5VIN TO 16VOUT WITH 0LFM 5VIN TO 16VOUT WITH 200LFM 5VIN TO 16VOUT WITH 400LFM 45 55 65 75 85 95 AMBIENT TEMPERATURE (C) 105 MAXIMUM LOAD CURRENT (A)
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 25 35 5VIN TO 16VOUT WITH 0LFM 5VIN TO 16VOUT WITH 200LFM 5VIN TO 16VOUT WITH 400LFM 45 55 65 75 85 95 AMBIENT TEMPERATURE (C) 105
4605 F09
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Figure 9. 5VIN to 16VOUT without Heatsink
Figure 10. 5VIN to 16VOUT with Heatsink
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LTM4605 TYPICAL APPLICATIONS
No Heat Sink
12 10 8 6 4 2 0 35 45 55 65 75 85 95 AMBIENT TEMPERATURE (C) 105 12 10 8 6 4 2 0 35 45 55 65 75 85 95 AMBIENT TEMPERATURE (C) 105
Power loss includes all external components BGA Heat Sink
MAXIMUM LOAD CURRENT (A)
20VIN TO 12VOUT WITH 0LFM 20VIN TO 12VOUT WITH 200LFM 20VIN TO 12VOUT WITH 400LFM
MAXIMUM LOAD CURRENT (A)
4605 F11
20VIN TO 12VOUT WITH 0LFM 20VIN TO 12VOUT WITH 200LFM 20VIN TO 12VOUT WITH 400LFM
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Figure 11. 20VIN to 12VOUT without Heatsink
Figure 12. 20VIN to 12VOUT with Heatsink
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APPLICATIONS INFORMATION
Table 4. 5V Output
DERATING CURVE Figure 7, 9 Figure 7, 9 Figure 7, 9 Figure 8, 10 Figure 8, 10 Figure 8, 10 VIN (V) 12, 16 12, 16 12, 16 12, 16 12, 16 12, 16 POWER LOSS CURVE Figure 5 Figure 5 Figure 5 Figure 5 Figure 5 Figure 5 AIR FLOW (LFM) 0 200 400 0 200 400 HEATSINK none none none BGA Heatsink BGA Heatsink BGA Heatsink JA (C/W)* 11.2 8.3 7.2 10.7 7.7 6.6
Table 5. 20V Input and 12V Output
DERATING CURVE Figure 11 Figure 11 Figure 11 Figure 12 Figure 12 Figure 12 VIN (V) 20 20 20 20 20 20 POWER LOSS CURVE Figure 6 Figure 6 Figure 6 Figure 6 Figure 6 Figure 6 AIR FLOW (LFM) 0 200 400 0 200 400 HEATSINK none none none BGA Heatsink BGA Heatsink BGA Heatsink JA (C/W)* 8.2 5.8 5.3 7.6 5.3 4.8
HEATSINK MANUFACTURER Wakefield Engineering
PART NUMBER LTN20069
PHONE NUMBER 603-635-2600
*The results of thermal resistance from junction to ambient JA are based on the demo board of DC1198A. Thus, the maximum temperature on board is treated as the junction temperature (which is in the Module 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 JA.
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Layout Checklist/Example 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. * 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. * Use a separated SGND ground copper area for components connected to signal pins. Connect the SGND to PGND underneath the unit. Figure 13. gives a good example of the recommended layout.
SW1 SW2 VIN
APPLICATIONS INFORMATION
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. * 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 the top layer and other power layers * Do not put vias directly on pads, unless the vias are capped.
CIN
VOUT
RSENSE
COUT
+ PGND
-
SGND PGND RSENSE
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KELVIN CONNECTIONS TO RSENSE
Figure 13. Recommended PCB Layout
TYPICAL APPLICATIONS
VIN 12V TO 20V CLOCK SYNC 10F 35V x2 ON/OFF PGOOD VIN RUN COMP INTVCC R1 1.5k R3 1k C3 0.1F PLLFLTR EXTVCC STBYMD SS SGND PGND LTM4605 SW1 SW2 RSENSE SENSE+ R2 8m SENSE- VFB RFB 7.15k
4605 TA02
PLLIN V OUT FCB L1 3.3H
+
100F 25V
VOUT 12V 12A
Figure 14. Buck Mode Operation with 12V to 20V Input
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TYPICAL APPLICATIONS
VIN 4.5V TO 12V CLOCK SYNC 4.7F 35V ON/OFF PGOOD VIN RUN COMP INTVCC R1 1.5k R3 1k PLLFLTR EXTVCC C3 0.1F STBYMD SS SGND PGND PLLIN V OUT FCB 2 SW1 SW2 RSENSE SENSE+ SENSE- VFB RFB 7.15k
4605 TA03
LTM4605
2200pF
22F 25V x2
+
330F 25V
VOUT 12V 5A
L1 3.3H
OPTIONAL FOR LOW SWITCHING NOISE R2 7m
Figure 15. Boost Mode Operation with 4.5V to 12V Input
VIN 4.5V TO 20V
CLOCK SYNC 10F 35V x2 PGOOD VIN ON/OFF RUN COMP INTVCC R1 1.5k R3 1k C3 0.1F PLLFLTR EXTVCC STBYMD SS SGND PGND LTM4605 SW1 SW2 RSENSE SENSE+ R2 7m SENSE- VFB RFB 7.15k
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PLLIN V OUT FCB L1 3.3H 22F 25V x2
+
330F 25V
VOUT 12V 5A
Figure 16. Wide Input Mode with 4.5V to 20V Input, 12V at 5A Output
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LTM4605 TYPICAL APPLICATIONS
VIN 4.5V TO 20V CLOCK SYNC 10F 35V x2 ON/OFF PGOOD VIN RUN COMP INTVCC R1 1.5k C3 R3 1k 0.1F PLLFLTR EXTVCC STBYMD SS SGND PGND LTM4605 SW1 SW2 RSENSE SENSE+ R2 8m SENSE- VFB RFB 19k
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PLLIN V OUT FCB L1 2.5H
+
100F 25V
VOUT 5V 12A
2
2200pF
OPTIONAL
Figure 17. 5V at 12A Design with Low Switching Noise (Optional)
VIN 4.5V TO 20V CLOCK SYNC 0 PHASE 10F 35V R5 100k PGOOD VIN RUN LTM4605 COMP INTVCC C1 0.1F R4 324k LTC6908-1 V+ GND SET OUT1 OUT2 MOD C3 0.1F SGND PGND 5.1V PLLFLTR EXTVCC STBYMD SS SENSE- VFB RFB 3.57k SW1 SW2 RSENSE SENSE+ R2 7m PLLIN V OUT FCB L1 3.3H C2 22F x2 VOUT 12V 10A
+
330F 25V
2-PHASE OSCILLATOR
CLOCK SYNC 180 PHASE 10F 35V PGOOD VIN RUN COMP INTVCC PLLFLTR EXTVCC STBYMD SS SGND SENSE- PGND VFB
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PLLIN V OUT FCB L2 3.3H C4 22F x2
+
LTM4605 SW1 SW2 RSENSE SENSE+
330F 25V
R3 7m
Figure 18. Two-Phase Parallel, 12V at 10A Design
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LGA Package 141-Lead (15mm x 15mm x 2.82mm)
(Reference LTC DWG # 05-08-1815 Rev A)
DETAIL A X Y M L K J H 15 BSC MOLD CAP SUBSTRATE 13.97 BSC G F E D C B A PADS SEE NOTES 12 3 DETAIL B 1.9050 3.1750 4.4450 5.7150 6.9850 0.630 0.025 SQ. 141x eee S X Y 11 10 9 8 7 6 5 4 3 2 1 PAD 1 2.72 - 2.92 0.12 - 0.28 13.97 BSC
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PACKAGE DESCRIPTION
aaa Z
15 BSC
0.27 - 0.37 2.45 - 2.55 DETAIL B bbb Z Z
PAD 1 CORNER
1.27 BSC
4
aaa Z
PACKAGE TOP VIEW
PACKAGE BOTTOM VIEW
6.9850
5.7150
4.4450
3.1750
1.9050
6.9850
5.7150
4.4450 DETAIL A
3.1750
1.9050
0.6350 0.0000 0.6350
NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 2. ALL DIMENSIONS ARE IN MILLIMETERS 3 4 LAND DESIGNATION PER JESD MO-222, SPP-010
LTMXXXXXX Module
COMPONENT PIN "A1"
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.
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 5. PRIMARY DATUM -Z- IS SEATING PLANE 6. THE TOTAL NUMBER OF PADS: 141 SYMBOL TOLERANCE 0.10 aaa 0.10 bbb 0.05 eee
TRAY PIN 1 BEVEL
0.6350 0.0000 0.6350
1.9050
3.1750
4.4450
5.7150
6.9850
PACKAGE IN TRAY LOADING ORIENTATION
LGA 141 1007 REV A
SUGGESTED PCB LAYOUT TOP VIEW
LTM4605
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Pin Assignment Table 6 (Arranged by Pin Number)
PIN NAME A1 A2 A3 A4 A5 A6 A7 A8 A9 PGND PGND PGND SENSE+ SENSE- SS SGND RUN FCB PIN NAME C1 C2 C3 C4 C5 C6 C7 C8 C9 PGND PGND PGND PGND PGND PGND PGND PGND PGND PIN NAME E1 E2 E3 E4 E5 E6 E7 E8 E9 VOUT VOUT PGND PGND PGND PGND PGND PGND PGND PIN NAME G1 G2 G3 G4 G5 G6 G7 G8 G9 VOUT VOUT VOUT VOUT RSENSE RSENSE RSENSE RSENSE RSENSE PIN NAME J1 J2 J3 J4 J5 J6 J7 J8 J9 SW1 SW1 SW1 SW1 RSENSE RSENSE RSENSE SW2 SW2 PIN NAME L1 L2 L3 L4 L5 L6 L7 L8 L9 SW1 SW1 SW1 SW1 RSENSE RSENSE SW2 SW2 SW2
PACKAGE DESCRIPTION
A10 STBYMD C10 PGND A11 PGND A12 PGND B1 B2 B3 B4 B5 B6 B7 B8 B9 PGND PGND PGND PGND PGOOD VFB COMP PLLIN C11 PGND C12 PGND D1 D2 D3 D4 D5 D6 D7 D9 PGND PGND PGND PGND PGND PGND PGND PGND PGND
E10 PGND E11 PGND E12 PGND F1 F2 F3 F4 F5 F6 F7 F8 F9 VOUT VOUT VOUT VOUT INTVCC EXTVCC - - -
G10 RSENSE G11 RSENSE G12 RSENSE H1 H2 H3 H4 H5 H6 H7 H8 H9 VOUT VOUT VOUT VOUT RSENSE RSENSE RSENSE RSENSE RSENSE
J10 VIN J11 VIN J12 VIN K1 K2 K3 K4 K5 K6 K7 K8 K9 SW1 SW1 SW1 SW1 RSENSE RSENSE SW2 SW2 SW2
L10 VIN L11 VIN M1 M2 M3 M4 M5 M6 M7 M8 M9 L12 VIN SW1 SW1 SW1 SW1 RSENSE RSENSE SW2 SW2 SW2
PLLFLTR D8
B10 PGND B11 PGND B12 PGND
D10 PGND D11 PGND D12 PGND
F10 RSENSE F11 RSENSE F12 RSENSE
H10 RSENSE H11 RSENSE H12 RSENSE
K10 VIN K11 VIN K12 VIN
M10 VIN M11 VIN M12 VIN
RELATED PARTS
PART NUMBER LTC2900 LTC2923 LTC3780 LTC3785 LT3825/LT3837 LTM4600 LTM4601/ LTM4601A LTM4602 LTM4603 LTM4604 DESCRIPTION Quad Supply Monitor with Adjustable Reset Timer Power Supply Tracking Controller 36V Buck-Boost Controller 10V Buck-Boost Controller Synchronous Isolated Flyback Controllers 10A DC/DC Module 12A DC/DC Module with PLL, Output Tracking/ Margining and Remote Sensing 6A DC/DC Module 6A DC/DC Module with PLL and Output Tracking/ Margining and Remote Sensing 4A Low Voltage DC/DC Module COMMENTS Monitors Four Supplies; Adjustable Reset Timer Tracks Both Up and Down; Power Supply Sequencing Synchronous Operation, Single Inductor Synchronous Operation, No RSENSETM, 2.7V VIN 10V, 2.7V VOUT 10V No Optocoupler Required; 3.3V, 12A Output; Simple Design Basic 10A DC/DC Module Synchronizable, PolyPhase Operation to 48A, LTM4601-1 Version has no Remote Sensing Pin Compatible with the LTM4600 Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote Sensing, Pin Compatible with the LTM4601 2.375 VIN 5V, 0.8V VOUT 5V, 9mm x 15mm x 2.3mm Package
No RSENSE is a Trademark of Linear Technology Corporation.
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24 Linear Technology Corporation
(408) 432-1900
LT 0108 REV A * PRINTED IN USA
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Price & Availability of LTM4605

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