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LTM4614 Dual 4A per Channel Low VIN DC/DC Module Regulator
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FEATURES
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DESCRIPTION
The LTM(R)4614 is a complete 4A dual output switching mode DC/DC power supply. Included in the package are the switching controllers, power FETs, inductors and all support components. The dual 4A DC/DC converters operate over an input voltage range of 2.375V to 5.5V. The LTM4614 supports output voltages ranging from 0.8V to 5V. The regulator output voltages are set by a single resistor for each output. Only bulk input and output capacitors are needed to complete the design. The low profile package (2.82mm) enables utilization of unused space on the bottom of PC boards for high density point of load regulation. Additional features include overvoltage protection, foldback overcurrent protection, thermal shutdown and programmable soft-start. The power module is offered in a space saving and thermally enhanced 15mm x 15mm x 2.82mm LGA package. The LTM4614 is Pb-free and RoHS compliant.
Different Combinations of Input and Output Voltages
NUMBER OF INPUTS 2 2 (Current Share, Ex. 3.3V and 5V) 1 1 NUMBER OF OUTPUTS 2 1 2 1 IOUT(MAX) 4A, 4A 8A 4A, 4A 8A, see LTM4608A
Dual 4A Output Power Supply Input Voltage Range: 2.375V to 5.5V 4A DC Typical, 5A Peak Output Current Each 0.8V Up to 5V Output Each, Parallelable 2% Total DC Output Error (0C TJ 125C) Output Voltage Tracking Up to 95% Efficiency Programmable Soft-Start Short-Circuit and Overtemperature Protection Power Good Indicators Small and Very Low Profile Package: 15mm x 15mm x 2.82mm
APPLICATIONS
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Telecom and Networking Equipment FPGA Power SERDES and Other Low Noise Applications
L, LT, LTC, LTM, Module, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131, 6724174.
TYPICAL APPLICATION
Dual Output 4A DC/DC Module Regulator
VIN1 3.3V TO 5V 10F LTM4614 VIN2 3.3V TO 5V 10F GND1 VIN2 VOUT2 FB2 5.76k GND2 75
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Efficiency vs Output Current
(R)
91 89
VIN = 3.3V
VIN1
VOUT1 FB1 10k 100F
EFFICIENCY (%)
VOUT1 1.2V/4A
87 85 83 81 79 VOUT 1.2V
VOUT 1.5V
VOUT2 1.5V/4A 100F
77 0 1 2 LOAD CURRENT (A) 3 4
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LTM4614 ABSOLUTE MAXIMUM RATINGS
(Note 1)
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PIN CONFIGURATION
(See Pin Functions, Pin Configuration Table)
TOP VIEW
M L K J H G F E D C B A 1 2 3 4 5 6 7 8 9 10 11 12
VIN1, VIN2, PGOOD1, PGOOD2 ..................... -0.3V to 6V COMP1, COMP2, RUN/SS1, RUN/SS2 FB1, FB2,TRACK1, TRACK2 ........................ -0.3V to VIN SW1, SW2, VOUT1, VOUT2 .............. -0.3V to (VIN + 0.3V) Internal Operating Temperature Range (Note 2)..................................................-40C to 125C Junction Temperature ........................................... 125C Storage Temperature Range................... -55C to 125C Body Temperature, Solder Reflow (Note 3) ........... 245C
LGA PACKAGE 144-LEAD (15mm 15mm
2.8mm)
TJMAX = 125C, JC-BOT = 2-3C/W, JA = 15C/W, JC-TOP = 25C/W, Weight = 1.61g
ORDER INFORMATION
LEAD FREE FINISH LTM4614EV#PBF LTM4614IV#PBF TRAY LTM4614EV#PBF LTM4614IV#PBF PART MARKING* LTM4614V LTM4614V PACKAGE DESCRIPTION 144-Lead (15mm x 15mm x 2.8mm) LGA 144-Lead (15mm x 15mm x 2.8mm) LGA TEMPERATURE RANGE -40C to 125C -40C to 125C
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/
The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25C. VIN = 5V unless otherwise noted. Refer to Figure 1. Specified as each channel (Note 6).
SYMBOL VIN(DC) VOUT(DC) PARAMETER Input DC Voltage Output Voltage CIN = 22F COUT = 100F RFB = 5.76k , , VIN = 2.375V to 5.5V, IOUT = 0A to 4A (Note 5) 0C TJ 125C IOUT = 0A IOUT = 0A, CIN = 22F COUT = 100F VOUT = 1.5V , , VIN = 5.5V VIN = 2.375V, VOUT = 1.5V, Switching Continuous VIN = 5.5V, VOUT = 1.5V, Switching Continuous Shutdown, RUN = 0, VIN = 5V VIN = 2.375V, VOUT = 1.5V, IOUT = 4A VIN = 5.5V, VOUT = 1.5V, IOUT = 4A CONDITIONS
l
ELECTRICAL CHARACTERISTICS
MIN 2.375
TYP
MAX 5.5
UNITS V
l
1.460 1.45 1.6
1.49 1.49 2 0.35 20 35 7 3.15 1.35
1.508 1.512 2.3
V V V A mA mA A A A
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VIN(UVLO) IINRUSH(VIN) IQ(VIN)
Undervoltage Lockout Threshold Input Inrush Current at Start-Up Input Supply Bias Current
12
IS(VIN)
Input Supply Current
2
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LTM4614
ELECTRICAL CHARACTERISTICS
SYMBOL IOUT(DC) VOUT(LINE) VOUT VOUT(LOAD) VOUT VOUT(AC) fs Output Ripple Voltage Output Ripple Voltage Frequency Load Regulation Accuracy PARAMETER Output Continuous Current Range Line Regulation Accuracy
The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25C. VIN = 5V unless otherwise noted. Refer to Figure 1. Specified as each channel (Note 6).
CONDITIONS VIN = 3.3V, VOUT = 1.5V (Note 5) VOUT = 1.5V, VIN from 2.375V to 5.5V, IOUT = 0A VOUT = 1.5V, 0A to 4A (Note 5), VIN = 2.375V to 5.5V 0C TJ 125C IOUT = 0A, COUT = 100F (X5R) VIN = 5V, VOUT = 1.5V IOUT = 4A, VIN = 5V, VOUT = 1.5V COUT = 100F VOUT = 1.5V, RUN/SS = 10nF , , IOUT = 0A VIN = 3.3V VIN = 5V COUT = 100F VOUT = 1.5V, IOUT = 1A Resistive Load, , TRACK = VIN and RUN/SS = Float VIN = 5V Load: 0% to 50% to 0% of Full Load, COUT = 100F VIN = 5V, VOUT = 1.5V , Load: 0% to 50% to 0% of Full Load, VIN = 5V, VOUT = 1.5V COUT = 100F VIN = 5V, VOUT = 1.5V IOUT = 0A, VOUT = 1.5V
l l
MIN 0
TYP 0.1
MAX 4 0.3
UNITS A %
l
0.7 1.2 12 1.25
1.25 1.5
% % mVP-P MHz
VOUT(START) Turn-On Overshoot
20 20
mV mV
tSTART
Turn-On Time
0.5 25 10
ms mV s
VOUT(LS) tSETTLE IOUT(PK) VFB IFB VRUN ITRACK
Peak Deviation for Dynamic Load Settling Time for Dynamic Load Step Output Current Limit Voltage at FB Pin
8 0.792 0.788 0.6 0.8 0.8 0.2 0.75 0.2 30 0 4.96 4.99 7.5 90 0.8 5.025 150 0.808 0.810 0.9
A V V A V A mV V k %
RUN Pin On/Off Threshold TRACK Pin Current TRACK = 0.4V
VTRACK(OFFSET) Offset Voltage VTRACK(RANGE) Tracking Input Range RFBHI VPGOOD RPGOOD Resistor Between VOUT and FB Pins PGOOD Range PGOOD Resistance
Open-Drain Pull-Down
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 LTM4614E is guaranteed to meet performance specifications over the 0C to 125C internal operating temperature range. Specifications over the -40C to 125C internal operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTM4614I is guaranteed to meet specifications over the full internal operating temperature range. Note that the maximum ambient temperature is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors.
Note 3: See Application Note 100. Note 4: The IC has overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperatures will exceed 125C when overtemperature is activated. Continuous overtemperature activation can impair long-term reliability. Note 5: See output current derating curves for different VIN, VOUT and TA. Note 6: Two channels are tested separately and the specified test conditions are applied to each channel.
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LTM4614 TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Output Current VIN = 2.5V
100 95 90 EFFICIENCY (%) EFFICIENCY (%) 85 80 75 70 65 0 100 95 90 85 80 75 70 65 2 4
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Efficiency vs Output Current VIN = 3.3V
95 90 EFFICIENCY (%) 85 80 75 70 65
Efficiency vs Output Current VIN = 5V
VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V 1 3 OUTPUT CURRENT (A)
VOUT = 2.5V VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V 0 1 3 OUTPUT CURRENT (A) 2 4
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VOUT = 3.3V VOUT = 2.5V VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V 0 1 2 3 OUTPUT CURRENT (A) 4
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Minimum Input Voltage at 4A Load
3.5 3.0 2.5 VOUT (V) 2.0 1.5 1.0 0.5 0 VOUT = 3.3V VOUT = 2.5V VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V
Load Transient Response
Load Transient Response
ILOAD 2A/DIV VOUT 20mV/DIV
ILOAD 2A/DIV VOUT 20mV/DIV
VIN = 5V 20s/DIV VOUT = 1.2V COUT = 100F, 6.3V CERAMICS 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 VIN (V)
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VIN = 5V 20s/DIV VOUT = 1.5V COUT = 100F, 6.3V CERAMICS
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Load Transient Response
Load Transient Response
Load Transient Response
ILOAD 2A/DIV VOUT 20mV/DIV
ILOAD 2A/DIV
ILOAD 2A/DIV VOUT 20mV/DIV
VOUT 20mV/DIV
20s/DIV VIN = 5V VOUT = 1.8V COUT = 100F, 6.3V CERAMICS
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VIN = 5V 20s/DIV VOUT = 2.5V COUT = 100F, 6.3V CERAMICS
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VIN = 5V 20s/DIV VOUT = 3.3V COUT = 100F, 6.3V CERAMICS
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LTM4614
TYPICAL PERFORMANCE CHARACTERISTICS
Start-Up Start-Up
806 VOUT 1V/DIV VOUT 1V/DIV VFB (mV) VIN = 5V 200s/DIV VOUT = 2.5V COUT = 100F 4A LOAD (0.01F SOFT-START CAPACITOR)
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VFB vs Temperature
804 802
IIN 1A/DIV
IIN 1A/DIV
800 798
VIN = 5V 200s/DIV VOUT = 2.5V COUT = 100F NO LOAD (0.01F SOFT-START CAPACITOR)
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796 794 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
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Current Limit Foldback
1.6 1.4 1.2 1.0 VOUT (V) 0.8 0.6 0.4 VOUT = 1.5V VIN = 5V 0.2 VIN = 3.3V VIN = 2.5V 0 4 5 3 IIN 4A/DIV VOUT 0.5V/DIV
Short-Circuit Protection 1.5V Short, No Load
Short-Circuit Protection 1.5V Short, 4A Load
VOUT 0.5V/DIV
IIN 1A/DIV
20s/DIV
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100s/DIV
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7 6 OUTPUT CURRENT (A)
8
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LTM4614 PIN FUNCTIONS
VIN1, VIN2 (J1-J6, K1-K6); (C1-C6, D1-D6): Power Input Pins. Apply input voltage between these pins and GND pins. Recommend placing input decoupling capacitance directly between VIN pins and GND pins. VOUT1, VOUT2 (K9-K12, J9-J12, L9-L12, M9-M12); (C9-C12, D9-D12, E9-E12, F9-F12): Power Output Pins. Apply output load between these pins and GND pins. Recommend placing output decoupling capacitance directly between these pins and GND pins. Review Table 4. GND1, GND2, (G1-G12, H1, H7-H12, J7-J8, K7-K8, L1, L7-L8, M1-M8); (A1-A12, B1, B7-B12, C7-C8, D7-D8, E1, E7-E8, F1-F8): Power Ground Pins for Both Input and Output Returns. TRACK1, TRACK2 (L3, E3): Output Voltage Tracking Pins. When the module is configured as a master output, then a soft-start capacitor is placed on the RUN/SS pin to ground to control the master ramp rate, or an external ramp can be applied to the master regulator's track pin to control it. Slave operation is performed by putting a resistor divider from the master output to the ground, and connecting the center point of the divider to this pin on the slave regulator. If tracking is not desired, then connect the TRACK pin to VIN. Load current must be present for tracking. See Applications Information section.
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FB1, FB2 (L6, E6): The Negative Input of the Switching Regulators' Error Amplifier. Internally, these pins are connected to VOUT with a 4.99k precision resistor. Different output voltages can be programmed with an additional resistor between the FB and GND pins. Two power modules can current share when this pin is connected in parallel with the adjacent module's FB pin. See Applications Information section. COMP1, COMP2 (L5, E5): Current Control Threshold and Error Amplifier Compensation Point. The current comparator threshold increases with this control voltage. Two power modules can current share when this pin is connected in parallel with the adjacent module's COMP pin. Each channel has been internally compensated. See Applications Information section. PGOOD1, PGOOD2 (L4, E4): Output Voltage Power Good Indicator. Open-drain logic output that is pulled to ground when the output voltage is not within 7.5% of the regulation point. RUN/SS1, RUN/SS2 (L2, E2): Run Control and Soft-Start Pin. A voltage above 0.8V will turn on the module, and below 0.5V will turn off the module. This pin has a 1M resistor to VIN and a 1000pF capacitor to GND. See Applications Information section for soft-start information. SW1, SW2 (H2-H6, B2-B6): The switching node of the circuit is used for testing purposes. This can be connected to copper on the board for improved thermal performance.
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LTM4614
SIMPLIFIED BLOCK DIAGRAM
PGOOD 4.7F 6.3V VIN VIN 22F 2.375V TO 5.5V 6.3V
RUN/SS CSSEXT TRACK SUPPLY 4.99k 5.76k TRACK COMP
RSS 1M CSS 1000pF
M1 CONTROL, DRIVE POWER FETS M2
L C2 470pF R1 4.99k
VOUT 4.7F 6.3V
VOUT 1.5V 4A 100F X5R
INTERNAL COMP
GND
FB RFB 5.76k
SW
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Figure 1. Simplified LTM4614 Block Diagram of Each Switching Regulator Channel
DECOUPLING REQUIREMENTS
SYMBOL CIN COUT PARAMETER External Input Capacitor Requirement (VIN = 2.375V to 5.5V, VOUT = 1.5V) External Output Capacitor Requirement (VIN = 2.375V to 5.5V, VOUT = 1.5V)
TA = 25C. Use Figure 1 configuration for each channel.
MIN 22 66 100 TYP MAX UNITS F F
CONDITIONS IOUT = 4A IOUT = 4A
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LTM4614 OPERATION
LTM4614 POWER MODULE DESCRIPTION The LTM4614 is a standalone dual nonisolated switching mode DC/DC power supply. It can deliver up to 4A of DC output current for each channel with few external input and output capacitors. This module provides two precisely regulated output voltages programmable via one external resistor for each channel from 0.8V DC to 5V DC over a 2.375V to 5.5V input voltage. The typical application schematic is shown in Figure 12. The LTM4614 has two integrated constant frequency current mode regulators, with built-in power MOSFETs with fast switching speed. The typical switching frequency is 1.25MHz. With current mode control and internal feedback loop compensation, these switching regulators have sufficient stability margins and good transient performance under a wide range of operating conditions, and with a wide range of output capacitors, even all ceramic output capacitors. Current mode control provides cycle-by-cycle fast current limit. Besides, current limiting is provided in an overcurrent condition with thermal shutdown. In addition, internal overvoltage and undervoltage comparators pull the
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open-drain PGOOD outputs low if the particular output feedback voltage exits a 7.5% window around the regulation point. Furthermore, in an overvoltage condition, internal top FET, M1, is turned off and bottom FET, M2, is turned on and held on until the overvoltage condition clears, or current limit is exceeded. Pulling each specific RUN pin below 0.8V forces the specific regulator controller into its shutdown state, turning off both M1 and M2 for each power stage. At low load current, each regulator works in continuous current mode by default to achieve minimum output voltage ripple. The TRACK/SS pins are used for power supply tracking and soft-start programming for each specific regulator. See Applications Information section. The LTM4614 is internally compensated to be stable over the operating conditions. Table 4 provides a guideline for input and output capacitance for several operating conditions. The Linear Technology Module Power Design Tool will be provided for transient and stability analysis. The FB pins are used to program the specific output voltage with a single resistor to ground.
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LTM4614
APPLICATIONS INFORMATION
Dual Switching Regulator A typical LTM4614 application circuit is shown in Figure 12. External component selection is primarily determined by the maximum load current and output voltage. Refer to Table 4 for specific external capacitor requirements for a particular application. VIN to VOUT Step-Down Ratios There are restrictions in the maximum VIN and VOUT stepdown ratio than can be achieved for a given input voltage on the two switching regulators. The LTM4614 is 100% duty cycle, but the VIN to VOUT minimum dropout will be a function the load current. A typical 0.5V minimum is sufficient. Output Voltage Programming Each regulator channel has an internal 0.8V reference voltage. As shown in the Block Diagram, a 4.99k internal feedback resistor connects the VOUT and FB pins together. The output voltage will default to 0.8V with no feedback resistor. Adding a resistor RFB from the FB pin to GND programs the output voltage: VOUT = 0.8V * 4.99k + RFB RFB 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. The bulk capacitor can be a switcherrated electrolytic aluminum OS-CON capacitor for bulk input capacitance due to high inductance traces or leads. If a low inductance plane is used to power the device, then no input capacitance is required. The internal 4.7F ceramics on each channel input are typically rated for 1A of RMS ripple current up to 85C operation. The worst-case ripple current for the 4A maximum current is 2A or less. An additional 10F or 22F ceramic capacitor can be used to supplement the internal capacitor with an additional 1A to 2A ripple current rating. Output Capacitors The LTM4614 switchers are designed for low output voltage ripple on each channel. The bulk output capacitors are chosen with low enough effective series resistance (ESR) to meet the output voltage ripple and transient requirements. The output capacitors can be a low ESR tantalum capacitor, low ESR polymer capacitor or ceramic capacitor. The typical output capacitance range is 66F to 100F . Additional output filtering may be required by the system designer, if further reduction of output ripple or dynamic transient spike is required. Table 4 shows a matrix of different output voltages and output capacitors to minimize the voltage droop and overshoot during a 2A/s transient. The table optimizes total equivalent ESR and total bulk capacitance to maximize transient performance.
Table 1. FB Resistor Table vs Various Output Voltages
VOUT RFB 0.8V Open 1.2V 10k 1.5V 5.76k 1.8V 3.92k 2.5V 2.37k 3.3V 1.62k
Input Capacitors The LTM4614 module should be connected to a low AC impedance DC source. One 4.7F ceramic capacitor is included inside the module for each regulator channel. Additional input capacitors are needed if a large load step is required up to the full 4A level and for RMS ripple current requirements. A 47F bulk capacitor can be used for more input bulk capacitance. This 47F capacitor is only needed if the input source impedance is compromised by long inductive leads or traces.
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LTM4614 APPLICATIONS INFORMATION
Fault Conditions: Current Limit and Overcurrent Foldback The LTM4614 has current mode control, which inherently limits the cycle-by-cycle inductor current not only in steady-state operation, but also in transient. Along with foldback current limiting in the event of an overload condition, the LTM4614 has overtemperature shutdown protection that inhibits switching operation around 150C for each channel. Run Enable and Soft-Start The RUN/SS pins provide a dual function of enable and soft-start control for each channel. The RUN/SS pins are used to control turn on of the LTM4614. While each enable pin is below 0.5V, the LTM4614 will be in a low quiescent current state. At least a 0.8V level applied to the enable pins will turn on the LTM4614 regulators. This pin can be used to sequence the regulator channels. The soft-start control is provided by a 1M pull-up resistor (RSS) and a 1000pF capacitor (CSS) as drawn in the Block Diagram for each channel. An external capacitor can be applied to the RUN/SS pin to increase the soft-start time. A typical value is 0.01F. The approximate equation for soft-start: VIN t SOFTSTART =In * RSS * CSS VIN - 1.8V
VIN 3V TO 5.5V C1 22F 6.3V PGOOD1 R3 10k PGOOD1 VOUT1 C4 22F 6.3V 1.5V RFB1 10k RTB 4.99k FB1 COMP1 TRACK1 RTA 10k RUN/SS1 GND1 LTM4614 VIN1 VIN2 PGOOD2 VOUT2 FB2 COMP2 TRACK2 RUN/SS2 GND2 VIN OR CONTROL RAMP CSSEXT1 C2 22F 6.3V PGOOD2 R4 10k
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where RSS and CSS are shown in the Block Diagram of Figure 1, and 1.8V is the soft-start upper range. The soft-start function can also be used to control the output ramp-up time, so that another regulator can be easily tracked to it. Output Voltage Tracking Output voltage tracking can be programmed externally using the TRACK pins. Either output can be tracked up or down with another regulator. The master regulator's output is divided down with an external resistor divider that is the same as the slave regulator's feedback divider to implement coincident tracking. The LTM4614 uses a very accurate 4.99k resistor for the internal top feedback resistor. Figure 2 shows an example of coincident tracking. Equations: RFB1 * Master TRACK1= 4.99k + RFB1 4.99k Slave = 1+ * TRACK1 RFB1
1.2V 4A
1.5V 4A C7 100F 6.3V RFB2 5.76k
C3 100F 6.3V
C9 22F 6.3V
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Figure 2. Dual Outputs (1.5V and 1.2V) with Tracking
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LTM4614
APPLICATIONS INFORMATION
TRACK1 is the track ramp applied to the slave's track pin. TRACK1 applies the track reference for the slave output up to the point of the programmed value at which TRACK1 proceeds beyond the 0.8V reference value. The TRACK1 pin must go beyond the 0.8V to ensure the slave output has reached its final value. Ratiometric tracking can be achieved by a few simple calculations and the slew rate value applied to the master's TRACK pin. As mentioned above, the TRACK pin has a control range from 0V to 0.8V. The control ramp slew rate applied to the master's TRACK pin is directly equal to the master's output slew rate in Volts/Time. The equation: MR * 4.99k = R TB SR where MR is the master's output slew rate and SR is the slave's output slew rate in Volts/Time. When coincident tracking is desired, then MR and SR are equal, thus RTB is equal to 4.99k. RTA is derived from equation: R TA = 0.8V V VFB V + FB - TRACK 4.99k RFB R TB feedback resistor of the slave regulator in equal slew rate or coincident tracking, then RTA is equal to RFB with VFB = VTRACK. Therefore RTB = 4.99k and RTA = 10k in Figure 2. Figure 3 shows the output voltage tracking waveform for coincident tracking. In ratiometric tracking, a different slew rate maybe desired for the slave regulator. RTB can be solved for when SR is slower than MR. Make sure that the slave supply slew rate is chosen to be fast enough so that the slave output voltage will reach it final value before the master output. For example, MR = 2.5V/ms and SR = 1.8V/1ms. Then RTB = 6.98k. Solve for RTA to equal to 3.24k. The master output must be greater than the slave output for the tracking to work. Output load current must be present for tracking to operate properly during power down. Power Good PGOOD1 and PGOOD2 are open-drain pins that can be used to monitor valid output voltage regulation. These pins monitor a 7.5% window around the regulation point. COMP Pin This pin is the external compensation pin. The module has already been internally compensated for all output voltages. Table 4 is provided for most application requirements. The Linear Technology Module Power Design Tool will be provided for other control loop optimization.
where VFB is the feedback voltage reference of the regulator, and VTRACK is 0.8V. Since RTB is equal to the 4.99k top
MASTER OUTPUT OUTPUT VOLTAGE (V)
SLAVE OUTPUT
TIME
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Figure 3. Output Voltage Coincident Tracking
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LTM4614 APPLICATIONS INFORMATION
Parallel Switching Regulator Operation The LTM4614 switching regulators are inherently current mode control. Paralleling will have very good current sharing. This will balance the thermals on the design. Figure 13 shows a schematic of a parallel design. The voltage feedback equation changes with the variable N as channels are paralleled. The equation: 4.99k + RFB VOUT = 0.8V * N RFB N is the number of paralleled channels. Thermal Considerations and Output Current Derating The power loss curves in Figures 5 and 6 can be used in coordination with the load current de-rating curves in Figures 7 to 10 for calculating an approximate JA thermal resistance for the LTM4614 with various heat sinking
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and airflow conditions. Both of the LTM4614 outputs are at full 4A load current, and the power loss curves in Figures 5 and 6 are combine power losses plotted for both output voltages up to 4A each. The 4A output voltages are 1.2V and 3.3V. These voltages are chosen to include the lower and higher output voltage ranges for correlating the thermal resistance. Thermal models are derived from several temperature measurements in a controlled temperature chamber along with thermal modeling analysis. The junction temperatures are monitored while ambient temperature is increased with and without airflow. The junctions are maintained at ~120C while lowering output current or power while increasing ambient temperature. The 120C is chosen to allow for a 5C margin window relative to the maximum 125C. The decreased output current will decrease the internal module loss as ambient temperature is increased. The power loss curves in Figures 5 and 6 show this amount of power loss as a function of load current that is specified for both channels The monitored junction temperature of 120C minus the ambient operating temperature specifies how much
2.5
3.0 2.5 POWER LOSS (W) VIN = 5V 0 1 2 LOAD CURRENT (A) 3 4
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2.0 POWER LOSS (W)
2.0 1.5 1.0 0.5 0 VIN = 5V 0 1 2 3 LOAD CURRENT (A) 4
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1.5
1.0
0.5
0
Figure 5. 1.2V Power Loss
Figure 6. 3.3V Power Loss
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LTM4614
APPLICATIONS INFORMATION
module temperature rise can be allowed. As an example in Figure 7 the load current is de-rated to 3A for each channel with 0LFM at ~ 90C and the power loss for both channels at 5V to 1.2V at 3A output are ~1.5 watts. If the 90C ambient temperature is subtracted from the 120C maximum junction temperature, then the difference of 30C divided 1.5W equals a 20C/W thermal resistance. Table 2 specifies a 15C/W value which is close. Table 2 and Table 3 provide equivalent thermal resistances for 1.2V and 3.3V outputs with and without air flow and heat sinking. The combine power loss for the two 4A outputs can be summed together and multiplied by the thermal resistance values in Tables 2 and 3 for module temperature rise under the specified conditions. The printed circuit board is a 1.6mm thick four layer board with 2 ounce copper for the two outer layers and 1 ounce copper for the two inner layers. The PCB dimensions are 95mm x 76mm. The data sheet list the JP (junction to pin) and JC (junction to case) thermal resistances under the Pin Configuration diagram.
4.5 4.0 3.5 LOAD CURRENT (A) 3.0 2.5 400LFM NO HEAT SINK 2.0 1.5 1.0 0.5 0 40 50 60 70 80 90 100 110 120
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4.5 4.0 3.5 200LFM NO HEAT SINK LOAD CURRENT (A) 3.0 2.5 400LFM HEAT SINK 2.0 1.5 1.0 0.5 0 AMBIENT TEMPERATURE (C) 40 50 60 70 80 90 100 110 120
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200LFM HEAT SINK
0LFM NO HEAT SINK
0LFM HEAT SINK
AMBIENT TEMPERATURE (C)
Figure 7. 1.2V No Heat Sink (VIN = 5V)
Figure 8. 1.2V Heat Sink (VIN = 5V)
4.5 4.0 3.5 LOAD CURRENT (A) 3.0 200LFM NO HEAT SINK 2.5 2.0 1.5 1.0 0.5 0 40 50 60 70 80 90 100 110 120
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4.5 4.0 3.5 LOAD CURRENT (A) 3.0 2.5 2.0 1.5 1.0 0.5 0 40 50 60 70 80 90 100 110 120
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400LFM HEAT SINK 200LFM HEAT SINK 0LFM HEAT SINK
400LFM NO HEAT SINK
0LFM NO HEAT SINK
AMBIENT TEMPERATURE (C)
AMBIENT TEMPERATURE (C)
Figure 9. 3.3V No Heat Sink (VIN = 5V)
Figure 10. 3.3V Heat Sink (VIN = 5V)
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LTM4614 APPLICATIONS INFORMATION
Table 2. 1.2V Output
DERATING CURVE Figure 7 Figure 7 Figure 7 Figure 8 Figure 8 Figure 8 VIN (V) 5 5 5 5 5 5 POWER LOSS CURVE Figure 5 Figure 5 Figure 5 Figure 5 Figure 5 Figure 5 AIRFLOW (LFM) 0 200 400 0 200 400 HEAT SINK None None None
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JA (C/W) 15 12 10 12 9 7
BGA Heat Sink BGA Heat Sink BGA Heat Sink
Table 3. 3.3V Output
DERATING CURVE Figure 9 Figure 9 Figure 9 Figure 10 Figure 10 Figure 10 VIN (V) 5 5 5 5 5 5 POWER LOSS CURVE Figure 6 Figure 6 Figure 6 Figure 6 Figure 6 Figure 6 AIRFLOW (LFM) 0 200 400 0 200 400 HEAT SINK None None None BGA Heat Sink BGA Heat Sink BGA Heat Sink JA (C/W) 15 12 10 12 9 7
HEAT SINK MANUFACTURER Aavid
PART NUMBER 375424b00034G
PHONE NUMBER
603-635-2800
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LTM4614
APPLICATIONS INFORMATION
Safety Considerations The LTM4614 modules do not provide isolation from VIN to VOUT. There is no internal fuse. If required, a slow blow fuse with a rating twice the maximum input current needs to be provided to protect each unit from catastrophic failure. Layout Checklist/Example The high integration of LTM4614 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, GND and VOUT. It helps to minimize the PCB conduction loss and thermal stress. * Place high frequency ceramic input and output capacitors next to the VIN, GND and VOUT pins to minimize high frequency noise. * Place a dedicated power ground layer underneath the unit. * To minimize the via conduction loss and reduce module thermal stress, use multiple vias for interconnection between the top layer and other power layers. * Do not put via directly on pads unless the via is capped. Figure 11 gives a good example of the recommended layout.
GND1
I/O PINS
VOUT1
GND1
M CIN1 L COUT1 COUT2
VOUT1
VIN1
K J H G F GND1
GND1
GND2
CIN2 E D C B
VOUT2 COUT3 COUT4
VIN2
GND2
A 1 2 3 4 5 6 7 8 9 10 11 12 GND2
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GND2
GND2
I/O PINS
Figure 11. Recommended PCB Layout
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LTM4614 APPLICATIONS INFORMATION
VIN 2.375V TO 5.5V C1 22F 6.3V VIN1 PGOOD1 1V 4A C4 100F 6.3V R1 20k VOUT1 FB1 COMP1 VIN TRACK1 RUN/SS1 GND1 LTM4614 VIN2 PGOOD2 VOUT2 FB2 COMP2 TRACK2 RUN/SS2 GND2 VIN CSSEXT1 0.1F R2 10k C2 22F 6.3V X5R OR X7R
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1.2V 4A C5 100F 6.3V
+
C3 470F
C6 22F 6.3V
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Figure 12. Typical 2.375VIN to 5.5VIN, 1.2V and 1V at 4A Table 4. Output Voltage Response vs Component Matrix (Refer to Figure 12) 0A to 2.5A Load Step Typical Measured Values
COUT1 AND COUT2 CERAMIC VENDORS TDK Murata TDK Murata VALUE 22F 6.3V 22F 16V 100F 6.3V 100F 6.3V PART NUMBER C3216X7SOJ226M GRM31CR61C226KE15L C4532X5R0J107MZ GRM32ER60J107M COUT1 AND COUT2 BULK VENDORS VALUE Sanyo POSCAP Sanyo POSCAP CIN BULK VENDORS Sanyo POSCAP 150F 10V 220F 4V VALUE 100F 10V PART NUMBER 10TPD150M 4TPE220MF PART NUMBER 10CE100FH
VOUT CIN CIN COUT1 AND COUT2 COUT1 AND COUT2 (V) (CER) EACH (POSCAP) EACH (CERAMIC) (BULK)* 1.2 100F None 10F x2 100F 22F x2 , 1.2 100F 220F 10F x2 22F x1 1.2 100F None 10F x2 100F 22F x2 , 1.2 100F 220F 10F x2 22F x1 1.5 100F None 10F x2 100F 22F x2 , 1.5 100F 220F 10F x2 22F x1 1.5 100F None 10F x2 100F 22F x2 , 1.5 100F 220F 10F x2 22F x1 1.8 100F None 10F x2 100F 22F x2 , 1.8 100F 220F 10F x2 22F x1 1.8 100F 220F 10F x2 22F x1 None None 2.5 10F x2 22F x1 2.5 100F 150F 10F x2 22F x1 2.5 100F 150F 10F x2 22F x1 3.3 100F 150F 10F x2 22F x1 *Bulk capacitance is optional if VIN has very low input impedance.
ITH None None None None None None None None None None None None None None None
VIN (V) 5 5 3.3 3.3 5 5 3.3 3.3 5 5 3.3 5 5 3.3 5
DROOP PEAK-TO-PEAK (mV) DEVIATION 33 68 25 50 33 68 25 50 30 60 28 60 30 60 27 56 34 68 30 60 30 60 50 90 33 60 50 95 50 90
RECOVERY TIME (s) 11 9 8 10 11 11 10 10 12 12 12 10 10 12 12
LOAD STEP (A/s) 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5
RFB (k) 10 10 10 10 5.76 5.76 5.76 5.76 3.92 3.92 3.92 3.09 3.09 3.09 1.62
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LTM4614
APPLICATIONS INFORMATION
VIN 3V TO 5.5V C1 22F 6.3V VIN1 PGOOD PGOOD1 VOUT1 C4 100F 6.3V R1 4.99k VIN CSSEXT1 0.01F FB1 COMP1 TRACK1 RUN/SS1 GND1 LTM4614 VIN2 PGOOD2 VOUT2 FB2 COMP2 TRACK2 RUN/SS2 GND2 VIN 1.2V 8A C5 100F 6.3V X5R OR X7R C2 22F 6.3V X5R OR X7R
R2 5k
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Figure 13. LTM4614 Parallel 1.2V at 8A Design (Also, See the LTM4608A)
VIN 2.375V TO 5.5V C1 22F 6.3V X5R OR X7R R3 10k PGOOD1 1.8V 4A C4 22F 6.3V C3 100F 6.3V R1 4.02k VOUT1 FB1 COMP1 VIN CSSEXT 0.01F TRACK1 RUN/SS1 GND1 LTM4614 VIN1 VIN2 PGOOD2 VOUT2 FB2 COMP2 TRACK2 RUN/SS2 GND2 4.99k R2 5.76k 5.76k 1.8V C5 22F 6.3V 1.5V 4A C2 22F 6.3V X5R OR X7R R4 10k
C6 100F 6.3V
X5R OR X7R REFER TO TABLE 4
X5R OR X7R REFER TO TABLE 4
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Figure 14. 1.8V and 1.5V at 4A with Output Voltage Tracking Design
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LGA Package 144-Lead (15mm x 15mm x 2.82mm)
(Reference LTC DWG # 05-08-1816 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 11 3 DETAIL B 1.9050 3.1750 4.4450 5.7150 6.9850 0.630 0.025 SQ. 143x eee S X Y 10 9 8 7 6 5 4 3 2 1 DIA 0.630 PAD 1 2.72 - 2.92 0.12 - 0.28 13.97 BSC 3x, C (0.22 x45)
LTM4614
PACKAGE DESCRIPTION
aaa Z
PACKAGE TOP VIEW
bbb Z
4
Z
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
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0.27 - 0.37 2.45 - 2.55 DETAIL B 1.27 BSC
aaa Z
15 BSC
PAD 1 CORNER
PACKAGE BOTTOM VIEW
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 mModule
COMPONENT PIN "A1"
0.6350 0.0000 0.6350
1.9050
3.1750
4.4450
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
5.7150
5. PRIMARY DATUM -Z- IS SEATING PLANE 6. THE TOTAL NUMBER OF PADS: 144 SYMBOL TOLERANCE 0.10 aaa 0.10 bbb eee 0.05
TRAY PIN 1 BEVEL PACKAGE IN TRAY LOADING ORIENTATION
LGA 144 0308 REV A
6.9850
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SUGGESTED PCB LAYOUT TOP VIEW
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LTM4614
PACKAGE DESCRIPTION
LTM4614 Component LGA Pinout
PIN ID A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 PIN ID G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 FUNCTION GND2 GND2 GND2 GND2 GND2 GND2 GND2 GND2 GND2 GND2 GND2 GND2 FUNCTION GND1 GND1 GND1 GND1 GND1 GND1 GND1 GND1 GND1 GND1 GND1 GND1 PIN ID B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 PIN ID H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 FUNCTION GND2 SW2 SW2 SW2 SW2 SW2 GND2 GND2 GND2 GND2 GND2 GND2 FUNCTION GND1 SW1 SW1 SW1 SW1 SW1 GND1 GND1 GND1 GND1 GND1 GND1 PIN ID C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 PIN ID J1 J2 J3 J4 J5 J6 J7 J8 J9 J10 J11 J12 FUNCTION VIN2 VIN2 VIN2 VIN2 VIN2 VIN2 GND2 GND2 VOUT2 VOUT2 VOUT2 VOUT2 FUNCTION VIN1 VIN1 VIN1 VIN1 VIN1 VIN1 GND1 GND1 VOUT1 VOUT1 VOUT1 VOUT1 PIN ID D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 PIN ID K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 K11 K12 FUNCTION VIN2 VIN2 VIN2 VIN2 VIN2 VIN2 GND2 GND2 VOUT2 VOUT2 VOUT2 VOUT2 FUNCTION VIN1 VIN1 VIN1 VIN1 VIN1 VIN1 GND1 GND1 VOUT1 VOUT1 VOUT1 VOUT1 PIN ID E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 E11 E12 PIN ID L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 FUNCTION GND2 RUN/SS2 TRACK2 PGOOD2 COMP2 FB2 GND2 GND2 VOUT2 VOUT2 VOUT2 VOUT2 FUNCTION GND1 RUN/SS1 TRACK1 PGOOD1 COMP1 FB1 GND1 GND1 VOUT1 VOUT1 VOUT1 VOUT1 PIN ID F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 PIN ID M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 FUNCTION GND2 GND2 GND2 GND2 GND2 GND2 GND2 GND2 VOUT2 VOUT2 VOUT2 VOUT2 FUNCTION GND1 GND1 GND1 GND1 GND1 GND1 GND1 GND1 VOUT1 VOUT1 VOUT1 VOUT1
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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.
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LTM4614 PACKAGE PHOTOGRAPH
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RELATED PARTS
PART NUMBER LTC(R)2900 LTC2923 LTM4600HV LTM4600HVMP LTM4601A LTM4602 LTM4603 LTM4604A LTM4605 LTM4607 LTM4608A LTM4615 LTM4616 LTM8020 LTM8021 LTM8022 LTM8023 DESCRIPTION Quad Supply Monitor with Adjustable Reset Timer Power Supply Tracking Controller 10A DC/DC Module Wide Temperature Range 10A DC/DC Module COMMENTS Monitors Four Supplies, Adjustable Reset Timer Tracks Both Up and Down, Power Supply Sequencing 4.5V VIN 28V, 0.6V VOUT 5V, LGA Package Guaranteed Operation from -55C to 125C Ambient, LGA Package
12A DC/DC Module with PLL, Output Tracking/Margining Synchronizable PolyPhase(R) Operation, LTM4601-1/LTM4601A-1 Version Has No Remote Sensing, LGA Package and Remote Sensing 6A DC/DC Module 6A DC/DC Module with PLL and Output Tracking/ Margining and Remote Sensing Low VIN 4A DC/DC Module 5A to 12A Buck-Boost Module 5A to 12A Buck-Boost Module Low VIN 8A DC/DC Step-Down Module Triple Low VIN DC/DC Module Dual 8A DC/DC Module High VIN 0.2A DC/DC Step-Down Module High VIN 0.5A DC/DC Step-Down Module High VIN 1A DC/DC Step-Down Module High VIN 2A DC/DC Step-Down Module Pin Compatible with the LTM4600, LGA Package Synchronizable, PolyPhase Operation, LTM4603-1 Version Has No Remote Sensing, Pin Compatible with the LTM4601, LGA Package 2.375V VIN 5.5V, 0.8V VOUT 5V, 9mm x 15mm x 2.3mm LGA Package 4.5V VIN 20V, 0.8V VOUT 16V, 15mm x 15mm x 2.8mm LGA Package 4.5V VIN 36V, 0.8V VOUT 25V, 15mm x 15mm x 2.8mm LGA Package 2.7V VIN 5.5V, 0.6V VOUT 5V, 9mm x 15mm x 2.8mm LGA Package Two 4A Outputs and One 1.5A Output; 15mm x 15mm x 2.8mm Current Share Inputs or Outputs; 15mm x 15mm x 2.8mm 4V VIN 36V, 1.25V VOUT 5V, 6.25mm x 6.25mm x 2.3mm LGA Package 3V VIN 36V, 0.4V VOUT 5V, 6.25mm x 11.25mm x 2.8mm LGA Package 3.6V VIN 36V, 0.8V VOUT 10V, 11.25mm x 9mm x 2.8mm LGA Package 3.6V VIN 36V, 0.8V VOUT 10V, 11.25mm x 9mm x 2.8mm LGA Package
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PolyPhase is a registered trademark of Linear Technology Corporation.
20 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0809 REV A * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2009

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