LTM4614 Dual 4A per Channel Low VIN DC/DC Module Regulator Features n n n n n n n n n n n Description 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% Max 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 n n 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 RoHS compliant with Pb-free finish. Applications n The LTM(R)4614 is a complete 4A dual output switching mode step-down Module(R) regulator. 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. 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 and LTpowerCAD is a trademark 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. Different Combinations of Input and Output Voltages NUMBER OF INPUTS NUMBER OF OUTPUTS IOUT(MAX) 2 2 4A, 4A 2 (Current Share, Ex. 3.3V and 5V) 1 8A 1 2 4A, 4A 1 1 8A, see LTM4608A Typical Application Efficiency vs Output Current Dual Output 4A DC/DC Module Regulator 91 VIN = 3.3V 89 VIN1 FB1 10F 10k LTM4614 VIN2 3.3V TO 5V VOUT1 1.2V/4A VOUT1 VIN2 VOUT2 1.5V/4A VOUT2 FB2 10F 5.76k GND1 100F 100F 87 EFFICIENCY (%) VIN1 3.3V TO 5V VOUT 1.5V 85 VOUT 1.2V 83 81 79 77 GND2 75 4614 F01a 0 1 2 LOAD CURRENT (A) 3 4 4614 TA01b 4614fb 1 LTM4614 Absolute Maximum Ratings Pin Configuration (See Pin Functions, Pin Configuration Table) (Note 1) 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 (Notes 2, 3)............................................. -40C to 125C Storage Temperature Range................... -55C to 125C Body Temperature, Solder Reflow.......................... 245C RUN/SS1 TOP VIEW PGOOD1 TRACK1 COMP1 FB1 M L VIN1 SW1 VOUT1 K J H GND1 G F E VIN2 VOUT2 D C SW2 B GND2 A 1 2 RUN/SS2 3 4 5 6 7 PGOOD2 TRACK2 COMP2 8 9 10 11 12 FB2 LGA PACKAGE 144-LEAD (15mm x 15mm x 2.82mm) TJMAX = 125C, JCbottom = 2-3C/W, JA = 15C/W, JCtop = 25C/W, Values Determined Using a 4-Layer 95mm x 76mm PCB, Weight = 1.7g Order Information LEAD FREE FINISH TRAY PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE (Note 2) LTM4614EV#PBF LTM4614EV#PBF LTM4614V 144-Lead (15mm x 15mm x 2.82mm) LGA -40C to 125C LTM4614IV#PBF LTM4614IV#PBF LTM4614V 144-Lead (15mm x 15mm x 2.82mm) LGA -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/ Electrical Characteristics The l denotes the specifications which apply over the full internal operating temperature range (Note 2), otherwise specifications are at TA = 25C. VIN = 5V unless otherwise noted. Refer to Figure 1. Specified as each channel (Note 5). SYMBOL PARAMETER VIN(DC) Input DC Voltage VOUT(DC) Output Voltage CONDITIONS MIN l 2.375 l 1.460 1.45 1.6 CIN = 22F, COUT = 100F, RFB = 5.76k VIN = 2.375V to 5.5V, IOUT = 0A to 4A (Note 4) 0C TJ 125C TYP MAX UNITS 5.5 V 1.49 1.49 1.508 1.512 V V 2 2.3 V 12 mA mA A VIN(UVLO) Undervoltage Lockout Threshold IOUT = 0A IINRUSH(VIN) Input Inrush Current at Start-Up IOUT = 0A, CIN = 22F, COUT = 100F, VOUT = 1.5V VIN = 5.5V 0.35 IQ(VIN) Input Supply Bias Current VIN = 2.375V, VOUT = 1.5V, Switching Continuous VIN = 5.5V, VOUT = 1.5V, Switching Continuous Shutdown, RUN = 0, VIN = 5V 20 35 7 A 4614fb 2 LTM4614 Electrical Characteristics The l denotes the specifications which apply over the full internal operating temperature range (Note 2), otherwise specifications are at TA = 25C. VIN = 5V unless otherwise noted. Refer to Figure 1. Specified as each channel (Note 5). SYMBOL PARAMETER CONDITIONS MIN IS(VIN) Input Supply Current VIN = 2.375V, VOUT = 1.5V, IOUT = 4A VIN = 5.5V, VOUT = 1.5V, IOUT = 4A IOUT(DC) Output Continuous Current Range VIN = 3.3V, VOUT = 1.5V (Note 4) VOUT(LINE) Line Regulation Accuracy VOUT = 1.5V, VIN from 2.375V to 5.5V, IOUT = 0A Load Regulation Accuracy VOUT = 1.5V, 0A to 4A (Note 4), VIN = 2.375V to 5.5V 0C TJ 125C TYP MAX 3.15 1.35 0 UNITS A A 4 A l 0.1 0.3 % l 0.7 1.2 1.25 1.5 % % VOUT VOUT(LOAD) VOUT VOUT(AC) Output Ripple Voltage IOUT = 0A, COUT = 100F (X5R) VIN = 5V, VOUT = 1.5V 12 fs Output Ripple Voltage Frequency IOUT = 4A, VIN = 5V, VOUT = 1.5V 1.25 MHz COUT = 100F, VOUT = 1.5V, RUN/SS = 10nF, IOUT = 0A VIN = 3.3V VIN = 5V 20 20 mV mV COUT = 100F, VOUT = 1.5V, IOUT = 1A Resistive Load, TRACK = VIN and RUN/SS = Float VIN = 5V 0.5 ms VOUT(START) Turn-On Overshoot tSTART Turn-On Time mVP-P VOUT(LS) Peak Deviation for Dynamic Load Load: 0% to 50% to 0% of Full Load, COUT = 100F, VIN = 5V, VOUT = 1.5V 25 mV tSETTLE Settling Time for Dynamic Load Step Load: 0% to 50% to 0% of Full Load, VIN = 5V, VOUT = 1.5V 10 s IOUT(PK) Output Current Limit COUT = 100F VIN = 5V, VOUT = 1.5V 8 A VFB Voltage at FB Pin IOUT = 0A, VOUT = 1.5V l 0.792 0.788 0.8 0.8 0.808 0.810 0.2 IFB VRUN RUN Pin On/Off Threshold ITRACK TRACK Pin Current VTRACK(OFFSET) Offset Voltage 0.6 TRACK = 0.4V VTRACK(RANGE) Tracking Input Range RFBHI Resistor Between VOUT and FB Pins VPGOOD PGOOD Range RPGOOD PGOOD Resistance 0.75 A 0.9 A 30 mV 0.8 4.99 5.025 7.5 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 LTM4614 is tested under pulsed load conditions such that TJ TA. 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 V 0.2 0 4.96 V V 90 V k % 150 temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. Note 3: 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 4: See output current derating curves for different VIN, VOUT and TA. Note 5: Two channels are tested separately and the specified test conditions are applied to each channel. 4614fb 3 LTM4614 Typical Performance Characteristics Efficiency vs Output Current VIN = 2.5V Efficiency vs Output Current VIN = 3.3V Efficiency vs Output Current VIN = 5V 95 95 90 90 90 85 80 75 65 0 1 85 80 VOUT = 2.5V VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V 75 VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V 70 70 2 3 OUTPUT CURRENT (A) 4 EFFICIENCY (%) 95 EFFICIENCY (%) 100 EFFICIENCY (%) 100 65 0 1 2 3 OUTPUT CURRENT (A) VOUT (V) 2.5 4 65 VOUT 20mV/DIV 1.0 20s/DIV VIN = 5V VOUT = 1.2V COUT = 100F, 6.3V CERAMICS 0.5 0 4 ILOAD 2A/DIV VOUT 20mV/DIV 1.5 1 2 3 OUTPUT CURRENT (A) Load Transient Response ILOAD 2A/DIV 2.0 0 4614 G03 Load Transient Response VOUT = 3.3V VOUT = 2.5V VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V VOUT = 3.3V VOUT = 2.5V VOUT = 1.8V VOUT = 1.5V VOUT = 1.2V VOUT = 0.8V 75 4614 G02 Minimum Input Voltage at 4A Load 3.0 80 70 4614 G01 3.5 85 20s/DIV VIN = 5V VOUT = 1.5V COUT = 100F, 6.3V CERAMICS 4614 G05 4614 G06 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 VIN (V) 4614 G04 Load Transient Response Load Transient Response Load Transient Response ILOAD 2A/DIV ILOAD 2A/DIV VOUT 20mV/DIV ILOAD 2A/DIV VOUT 20mV/DIV VOUT 20mV/DIV 20s/DIV VIN = 5V VOUT = 1.8V COUT = 100F, 6.3V CERAMICS 4614 G07 20s/DIV VIN = 5V VOUT = 2.5V COUT = 100F, 6.3V CERAMICS 4614 G08 20s/DIV VIN = 5V VOUT = 3.3V COUT = 100F, 6.3V CERAMICS 4614 G09 4614fb 4 LTM4614 Typical Performance Characteristics Start-Up Start-Up 806 VOUT 1V/DIV VFB vs Temperature 804 VOUT 1V/DIV VFB (mV) 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) 4614 G10 VIN = 5V 200s/DIV VOUT = 2.5V COUT = 100F 4A LOAD (0.01F SOFT-START CAPACITOR) 4614 G11 796 794 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 4614 G12 Short-Circuit Protection 1.5V Short, No Load Current Limit Foldback Short-Circuit Protection 1.5V Short, 4A Load 1.6 1.4 1.2 VOUT 0.5V/DIV VOUT 0.5V/DIV IIN 1A/DIV IIN 1A/DIV VOUT (V) 1.0 0.8 0.6 VOUT = 1.5V VIN = 5V 0.2 VIN = 3.3V VIN = 2.5V 0 4 5 3 0.4 7 6 OUTPUT CURRENT (A) 20s/DIV 4614 G14 100s/DIV 4614 G15 8 4614 G13 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. 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. VOUT1, VOUT2 (J9-J12, K9-K12, 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. 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. 4614fb 5 LTM4614 Pin Functions 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 the Applications Information section. 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 externally connected 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 the 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 the 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 Pins. A voltage above 0.9V will turn on the module, and below 0.6V will turn off the module. This pin has a 1M resistor to VIN and a 1000pF capacitor to GND. The voltage on the RUN/SS pin clamps the control loop's current comparator threshold. A RUN/SS pin voltage of 2.375V upon completion of soft-start guarantees the regulator can deliver full output current. To turn off the module while VIN remains active, the RUN/SS pin should be pulled low with a falling edge 1s to ensure the device does not transition slowly through the internal undervoltage lockout threshold. See Applications Information section for softstart 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. Simplified Block Diagram VIN PGOOD RUN/SS CSSEXT TRACK SUPPLY 4.99k TRACK 5.76k 4.7F 6.3V RSS 1M CSS 1000pF CONTROL, DRIVE POWER FETS COMP M1 0.47H M2 C2 470pF VOUT 1.5V 4A VOUT 4.7F 6.3V R1 4.99k INTERNAL COMP VIN 22F 2.375V TO 5.5V 6.3V 100F X5R GND FB RFB 5.76k SW 4614 F01 Figure 1. Simplified LTM4614 Block Diagram of Each Switching Regulator Channel 4614fb 6 LTM4614 Decoupling Requirements TA = 25C. Use Figure 1 configuration for each channel. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS CIN External Input Capacitor Requirement (VIN = 2.375V to 5.5V, VOUT = 1.5V) IOUT = 4A 22 F COUT External Output Capacitor Requirement (VIN = 2.375V to 5.5V, VOUT = 1.5V) IOUT = 4A 100 F 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 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 and RUN/SS pins are used for power supply tracking and soft-start programming for each specific regulator. See the 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 LTpowerCADTM GUI is available for transient and stability analysis. The FB pins are used to program the specific output voltage with a single externally connected resistor to ground. 4614fb 7 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 capable, but the VIN to VOUT minimum dropout will be a function the load current. A typical 0.5V minimum is sufficient. See Typical Performance Characteristics. 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 externally applied 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 aluminum electrolytic OS-CON or polymer capacitor. 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 worstcase ripple current for the 4A maximum current is 2A or less. An additional 10F or 22F local ceramic capacitor can be used to supplement the internal capacitor with an additional 1A to 2A ripple current rating. See Figure 11 for recommended PCB layout. Output Capacitors Table 1. FB Resistor Table vs Various Output Voltages VOUT 0.8V 1.0V 1.2V 1.5V 1.8V 2.5V 3.3V RFB Open 20k 10k 5.76k 3.92k 2.37k 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. 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 low ESR tantalum capacitors, low ESR polymer capacitors or ceramic capacitors. 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 spikes 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. See Figure 11 for recommended PCB layout. 4614fb 8 LTM4614 Applications Information Fault Conditions: Current Limit and Overcurrent Foldback 0.01F. Soft-start time is approximately given by: 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 0.6V, the LTM4614 will be in a low quiescent current state. At least a 0.9V level applied to the enable pins will turn on the LTM4614 regulators. The voltage on the RUN/SS pins clamp the control loop's current comparator threshold. A RUN/SS pin voltage of 2.375V upon completion of soft-start guarantees the regulator can deliver full output current. These pins can be used to sequence the regulator channels. Soft-start control is provided by a 1M pull-up resistor (RSS) and a 1000pF capacitor (CSS) as shown in the Block Diagram for each channel. Optionally, an external capacitor (CSSEXT) can be applied to the RUN/SS pin to increase soft-start time. A typical value is VIN t SOFTSTART =In *RSS * (CSS +CSSEXT ) VIN - 1.8V where RSS and CSS are shown in the Block Diagram of Figure 1, and 1.8V is the soft-start upper range. The softstart function can also be used to control the output rampup time, so that another regulator can be easily tracked to it. To turn off the module while VIN remains active, the RUN/SS pin should be pulled low with a falling edge 1s to ensure the device does not transition slowly through the internal undervoltage lockout threshold. 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 * TRACK1 Slave = 1+ RFB1 VIN 3V TO 5.5V C1 22F 6.3V PGOOD1 R3 10k 1.2V 4A PGOOD1 C2 22F 6.3V VIN1 VIN2 C3 100F 6.3V RFB1 10k FB1 RTB 4.99k RTA 10k PGOOD2 1.5V 4A VOUT2 VOUT1 C4 22F 6.3V 1.5V PGOOD2 R4 10k LTM4614 FB2 COMP1 COMP2 TRACK1 TRACK2 RUN/SS1 GND1 RUN/SS2 GND2 VIN OR CONTROL RAMP C7 100F 6.3V RFB2 5.76k C9 22F 6.3V CSSEXT1 4614 F02 Figure 2. Dual Outputs (1.5V and 1.2V) with Tracking 4614fb 9 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 where VFB is the feedback voltage reference of the regulator, and VTRACK is 0.8V. Since RTB is equal to the 4.99k top 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 LTpowerCAD GUI is available for other control loop optimization. OUTPUT VOLTAGE (V) MASTER OUTPUT SLAVE OUTPUT TIME 4614 F03 Figure 3. Output Voltage Coincident Tracking 4614fb 10 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 derating curves in Figures 7 to 10 for calculating an approximate JA thermal resistance for the LTM4614 with various heat sinking 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 combined 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) POWER LOSS (W) 2.0 1.5 1.0 0.5 0 2.0 1.5 1.0 0.5 VIN = 5V 0 1 2 LOAD CURRENT (A) 4 3 4614 F05 Figure 5. 1.2V Power Loss 0 VIN = 5V 0 1 2 3 LOAD CURRENT (A) 4 4614 F06 Figure 6. 3.3V Power Loss 4614fb 11 LTM4614 Applications Information heat sinking. The combined 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 lists the JA (junction to ambient) and JC (junction to case) thermal resistances under the Pin Configuration diagram. 4.5 4.5 4.0 4.0 3.5 3.5 200LFM NO HEAT SINK 3.0 2.5 LOAD CURRENT (A) LOAD CURRENT (A) module temperature rise can be allowed. As an example, in Figure 7 the load current is derated to 3A for each channel with 0LFM at ~ 90C and the total combined power loss for both channels at 5V to 1.2V at 3A output is ~1.5 watts. If the 90C ambient temperature is subtracted from the 120C maximum junction temperature, then the difference of 30C divided by 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 400LFM NO HEAT SINK 2.0 1.5 0LFM NO HEAT SINK 1.0 1.5 40 50 60 70 80 90 0 100 110 120 0LFM HEAT SINK 4.0 3.5 3.5 LOAD CURRENT (A) 4.5 200LFM NO HEAT SINK 400LFM NO HEAT SINK 2.0 1.5 0LFM NO HEAT SINK 1.0 60 70 80 90 100 110 120 4614 F08 Figure 8. 1.2V Heat Sink (VIN = 5V) 4.0 2.5 50 4614 F07 4.5 3.0 40 AMBIENT TEMPERATURE (C) Figure 7. 1.2V No Heat Sink (VIN = 5V) LOAD CURRENT (A) 400LFM HEAT SINK 2.0 0.5 AMBIENT TEMPERATURE (C) 3.0 400LFM HEAT SINK 2.5 200LFM HEAT SINK 2.0 0LFM HEAT SINK 1.5 1.0 0.5 0 200LFM HEAT SINK 2.5 1.0 0.5 0 3.0 0.5 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (C) 4614 F09 Figure 9. 3.3V No Heat Sink (VIN = 5V) 0 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (C) 4614 F10 Figure 10. 3.3V Heat Sink (VIN = 5V) 4614fb 12 LTM4614 Applications Information Table 2. 1.2V Output VIN (V) POWER LOSS CURVE AIRFLOW (LFM) HEAT SINK JA (C/W) Figure 7 DERATING CURVE 5 Figure 5 0 None 15 Figure 7 5 Figure 5 200 None 12 Figure 7 5 Figure 5 400 None 10 Figure 8 5 Figure 5 0 BGA Heat Sink 12 Figure 8 5 Figure 5 200 BGA Heat Sink 9 Figure 8 5 Figure 5 400 BGA Heat Sink 7 Table 3. 3.3V Output VIN (V) POWER LOSS CURVE AIRFLOW (LFM) HEAT SINK JA (C/W) Figure 9 DERATING CURVE 5 Figure 6 0 None 15 Figure 9 5 Figure 6 200 None 12 Figure 9 5 Figure 6 400 None 10 Figure 10 5 Figure 6 0 BGA Heat Sink 12 Figure 10 5 Figure 6 200 BGA Heat Sink 9 Figure 10 5 Figure 6 400 BGA Heat Sink 7 HEAT SINK MANUFACTURER PART NUMBER WEBSITE Aavid Thermalloy 375424b00034G www.aavid.com 4614fb 13 LTM4614 Applications Information Safety Considerations * Use large PCB copper areas for high current paths, including VIN, GND and VOUT. It helps to minimize the PCB conduction loss and thermal stress. The LTM4614 modules do not provide galvanic 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. * 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. 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. * 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 they are capped. * Refer to http://www.linear.com/docs/29812 for device land pattern and stencil design. I/O PINS GND1 GND1 Figure 11 gives a good example of the recommended layout. VOUT1 M VOUT1 CIN1 L VIN1 GND1 GND2 VIN2 COUT1 COUT2 K J H GND1 G F CIN2 E COUT3 COUT4 VOUT2 D C B GND2 A 1 2 3 4 GND2 5 6 7 I/O PINS 8 9 GND2 10 11 12 GND2 4614 F11 Figure 11. Recommended PCB Layout 4614fb 14 LTM4614 Applications Information VIN 2.375V TO 5.5V C2 22F 6.3V X5R OR X7R C1 22F 6.3V PGOOD1 1V 4A VIN2 VIN1 VOUT1 + C3 470F FB1 C4 100F 6.3V R1 20k VIN PGOOD2 1.2V 4A VOUT2 FB2 LTM4614 COMP1 COMP2 TRACK1 TRACK2 RUN/SS1 GND1 R2 10k VIN RUN/SS2 GND2 C5 100F 6.3V C6 22F 6.3V CSSEXT1 0.1F 4614 F12 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 VALUE PART NUMBER COUT1 AND COUT2 BULK VENDORS VALUE PART NUMBER TDK 22F 6.3V C3216X7SOJ226M Sanyo POSCAP 150F 10V 10TPD150M Murata 22F 16V GRM31CR61C226KE15L Sanyo POSCAP 220F 4V 4TPE220MF TDK 100F 6.3V C4532X5R0J107MZ CIN BULK VENDORS VALUE PART NUMBER Murata 100F 6.3V GRM32ER60J107M SUNCON 100F 10V 10CE100FH VOUT CIN CIN COUT1 AND COUT2 COUT1 AND COUT2 (V) (CERAMIC) (BULK)* (CER) EACH (POSCAP) EACH 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 2.5 None None 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 2.37 2.37 2.37 1.62 4614fb 15 LTM4614 Applications Information VIN 3V TO 5.5V C2 22F 6.3V X5R OR X7R C1 22F 6.3V R2 5k PGOOD PGOOD1 VIN1 VIN2 PGOOD2 VOUT1 C4 100F 6.3V FB1 VIN C5 100F 6.3V X5R OR X7R COMP2 TRACK1 VIN TRACK2 RUN/SS1 GND1 CSSEXT1 0.01F FB2 LTM4614 COMP1 R1 4.99k 1.2V 8A VOUT2 RUN/SS2 GND2 4614 F13 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 C2 22F 6.3V X5R OR X7R PGOOD1 1.8V 4A VIN1 VIN2 VOUT1 C3 100F 6.3V FB1 C4 22F 6.3V R1 4.02k X5R OR X7R REFER TO TABLE 4 VIN CSSEXT 0.01F R4 10k PGOOD2 1.5V 4A VOUT2 LTM4614 FB2 COMP2 TRACK1 TRACK2 4.99k RUN/SS2 GND2 5.76k RUN/SS1 GND1 C5 22F 6.3V 1.8V COMP1 C6 100F 6.3V R2 5.76k X5R OR X7R REFER TO TABLE 4 4614 F14 Figure 14. 1.8V and 1.5V at 4A with Output Voltage Tracking Design 4614fb 16 4 3.1750 1.9050 3.1750 SUGGESTED PCB LAYOUT TOP VIEW 0.6350 0.0000 0.6350 PACKAGE TOP VIEW E 1.9050 PIN "A1" CORNER 6.9850 5.7150 4.4450 4.4450 5.7150 6.9850 aaa Z Y 6.9850 5.7150 4.4450 3.1750 1.9050 0.6350 0.0000 0.6350 1.9050 3.1750 4.4450 5.7150 6.9850 X D aaa Z bbb Z 0.27 2.45 MIN 2.72 0.60 NOM 2.82 0.63 15.00 15.00 1.27 13.97 13.97 0.32 2.50 DIMENSIONS eee S X Y H1 SUBSTRATE 0.37 2.55 0.15 0.10 0.05 MAX 2.92 0.66 NOTES DETAIL B PACKAGE SIDE VIEW A TOTAL NUMBER OF LGA PADS: 144 SYMBOL A b D E e F G H1 H2 aaa bbb eee DETAIL A 0.630 0.025 SQ. 143x DETAIL B H2 MOLD CAP Z (Reference LTC DWG # 05-08-1816 Rev B) LGA Package 144-Lead (15mm x 15mm x 2.82mm) e b 11 10 9 3x, C (0.22 x45) 7 G 6 e 5 PACKAGE BOTTOM VIEW 8 4 3 1 DETAIL A 2 DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE 4 TRAY PIN 1 BEVEL LGA 144 1111 REV B PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX Module 5. PRIMARY DATUM -Z- IS SEATING PLANE BALL DESIGNATION PER JESD MS-028 AND JEP95 3 2. ALL DIMENSIONS ARE IN MILLIMETERS NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 COMPONENT PIN "A1" 3 SEE NOTES F b 12 A B C D E F G H J K L M DIA 0.630 PAD 1 LTM4614 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. 4614fb 17 LTM4614 Package Description LTM4614 Component LGA Pinout PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION A1 GND2 B1 GND2 C1 VIN2 D1 VIN2 E1 GND2 F1 GND2 A2 GND2 B2 SW2 C2 VIN2 D2 VIN2 E2 RUN/SS2 F2 GND2 A3 GND2 B3 SW2 C3 VIN2 D3 VIN2 E3 TRACK2 F3 GND2 A4 GND2 B4 SW2 C4 VIN2 D4 VIN2 E4 PGOOD2 F4 GND2 A5 GND2 B5 SW2 C5 VIN2 D5 VIN2 E5 COMP2 F5 GND2 A6 GND2 B6 SW2 C6 VIN2 D6 VIN2 E6 FB2 F6 GND2 A7 GND2 B7 GND2 C7 GND2 D7 GND2 E7 GND2 F7 GND2 A8 GND2 B8 GND2 C8 GND2 D8 GND2 E8 GND2 F8 GND2 A9 GND2 B9 GND2 C9 VOUT2 D9 VOUT2 E9 VOUT2 F9 VOUT2 A10 GND2 B10 GND2 C10 VOUT2 D10 VOUT2 E10 VOUT2 F10 VOUT2 A11 GND2 B11 GND2 C11 VOUT2 D11 VOUT2 E11 VOUT2 F11 VOUT2 A12 GND2 B12 GND2 C12 VOUT2 D12 VOUT2 E12 VOUT2 F12 VOUT2 PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION G1 GND1 H1 GND1 J1 VIN1 K1 VIN1 L1 GND1 M1 GND1 G2 GND1 H2 SW1 J2 VIN1 K2 VIN1 L2 RUN/SS1 M2 GND1 G3 GND1 H3 SW1 J3 VIN1 K3 VIN1 L3 TRACK1 M3 GND1 G4 GND1 H4 SW1 J4 VIN1 K4 VIN1 L4 PGOOD1 M4 GND1 G5 GND1 H5 SW1 J5 VIN1 K5 VIN1 L5 COMP1 M5 GND1 G6 GND1 H6 SW1 J6 VIN1 K6 VIN1 L6 FB1 M6 GND1 G7 GND1 H7 GND1 J7 GND1 K7 GND1 L7 GND1 M7 GND1 G8 GND1 H8 GND1 J8 GND1 K8 GND1 L8 GND1 M8 GND1 G9 GND1 H9 GND1 J9 VOUT1 K9 VOUT1 L9 VOUT1 M9 VOUT1 G10 GND1 H10 GND1 J10 VOUT1 K10 VOUT1 L10 VOUT1 M10 VOUT1 G11 GND1 H11 GND1 J11 VOUT1 K11 VOUT1 L11 VOUT1 M11 VOUT1 G12 GND1 H12 GND1 J12 VOUT1 K12 VOUT1 L12 VOUT1 M12 VOUT1 4614fb 18 LTM4614 Revision History (Revision history begins at Rev B) REV DATE DESCRIPTION B 08/12 Update Pin Configuration drawing. PAGE NUMBER Remove reference to obsolete Application Note. Correct typical performance curves. 2 3 4 and 5 Clarify RUN/SS and FB Pin Function information. 6 Update Block Diagram. 6 Clarify RUN/SS Applications Information. 9 Correct feedback resistor value. 15 4614fb 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. 19 LTM4614 Package Photograph Related Parts PART NUMBER DESCRIPTION COMMENTS LTC(R)2900 Quad Supply Monitor with Adjustable Reset Timer Monitors Four Supplies, Adjustable Reset Timer LTC2923 Power Supply Tracking Controller Tracks Both Up and Down, Power Supply Sequencing LTM4600HV 10A DC/DC Module Regulator 4.5V VIN 28V, 0.6V VOUT 5V, LGA Package LTM4600HVMP Wide Temperature Range 10A DC/DC Module Regulator Guaranteed Operation from -55C to 125C Ambient, LGA Package LTM4601A 12A DC/DC Module Regulator with PLL, Output Tracking/Margining and Remote Sensing Synchronizable PolyPhase(R) Operation, LTM4601-1/LTM4601A-1 Version Has No Remote Sensing, LGA Package LTM4602 6A DC/DC Module Regulator Pin Compatible with the LTM4600, LGA Package LTM4603 6A DC/DC Module Regulator with PLL and Output Tracking/Margining and Remote Sensing Synchronizable, PolyPhase Operation, LTM4603-1 Version Has No Remote Sensing, Pin Compatible with the LTM4601, LGA Package LTM4604A Low VIN 4A DC/DC Module Regulator 2.375V VIN 5.5V, 0.8V VOUT 5V, 9mm x 15mm x 2.32mm LGA Package LTM4605 5A to 12A Buck-Boost Module Regulator 4.5V VIN 20V, 0.8V VOUT 16V, 15mm x 15mm x 2.82mm LGA Package LTM4607 5A to 12A Buck-Boost Module Regulator 4.5V VIN 36V, 0.8V VOUT 25V, 15mm x 15mm x 2.82mm LGA Package LTM4608A Low VIN 8A DC/DC Step-Down Module Regulator 2.7V VIN 5.5V, 0.6V VOUT 5V, 9mm x 15mm x 2.82mm LGA Package LTM4615 Triple Low VIN DC/DC Module Regulator Two 4A Outputs and One 1.5A Output; 15mm x 15mm x 2.82mm LTM4616 Dual 8A DC/DC Module Regulator Current Share Inputs or Outputs; 15mm x 15mm x 2.82mm LTM8020 High VIN 0.2A DC/DC Step-Down Module Regulator 4V VIN 36V, 1.25V VOUT 5V, 6.25mm x 6.25mm x 2.32mm LGA Package LTM8021 High VIN 0.5A DC/DC Step-Down Module Regulator 3V VIN 36V, 0.4V VOUT 5V, 6.25mm x 11.25mm x 2.82mm LGA Package LTM8022 High VIN 1A DC/DC Step-Down Module Regulator 3.6V VIN 36V, 0.8V VOUT 10V, 11.25mm x 9mm x 2.82mm LGA Package LTM8023 High VIN 2A DC/DC Step-Down Module Regulator 3.6V VIN 36V, 0.8V VOUT 10V, 11.25mm x 9mm x 2.82mm LGA Package PolyPhase is a registered trademark of Linear Technology Corporation. 4614fb 20 Linear Technology Corporation LT 0812 REV B * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com LINEAR TECHNOLOGY CORPORATION 2009