LTM4608A Low VIN, 8A DC/DC µModule Regulator with Tracking, Margining, and Frequency Synchronization DESCRIPTION FEATURES Complete Standalone Power Supply n±1.75% Total DC Output Error (–55°C to 125°C) n 2.7V to 5.5V Input Voltage Range n 8A DC, 10A Peak Output Current n 0.6V Up to 5V Output n Output Voltage Tracking and Margining n Power Good Tracks Margining n Multiphase Operation n Parallel Current Sharing n Onboard Frequency Synchronization n Spread Spectrum Frequency Modulation n Overcurrent/Thermal Shutdown Protection n Current Mode Control/Fast Transient Response n Selectable Burst Mode® Operation n Up to 95% Efficiency n Output Overvoltage Protection n Small, Low Profile 9mm × 15mm × 2.8mm LGA Package (0.630mm Pads) The LTM®4608A is a complete 8A switch mode DC/DC power supply with ±1.75% total output voltage error. Included in the package are the switching controller, power FETs, inductor and all support components. Operating over an input voltage range of 2.7V to 5.5V, the LTM4608A supports an output voltage range of 0.6V to 5V, set by a single external resistor. This high efficiency design delivers up to 8A continuous current (10A peak). Only bulk input and output capacitors are needed to complete the design. n The low profile package (2.8mm) enables utilization of unused space on the back side of PC boards for high density point-of-load regulation. The 0.630mm LGA pads with 1.27mm pitch simplify PCB layout by providing standard trace routing and via placement. The high switching frequency and current mode architecture enable a very fast transient response to line and load changes without sacrificing stability. The device supports frequency synchronization, programmable multiphase and/or spread spectrum operation, output voltage tracking for supply rail sequencing and voltage margining. APPLICATIONS Telecom, Networking and Industrial Equipment Storage Systems n Point of Load Regulation n Fault protection features include overvoltage protection, overcurrent protection and thermal shutdown. The power module is offered in a compact and thermally enhanced 9mm × 15mm × 2.8mm surface mount LGA package. The LTM4608A is Pb-free and RoHS compliant. n L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, µModule and PolyPhase 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. TYPICAL APPLICATION Efficiency vs Load Current 100 2.7V to 5.5V Input to 1.8V Output DC/DC µModule® Regulator CLKIN CLKIN VIN 10µF 95 SVIN FB SW RUN VOUT 1.8V VOUT LTM4608A ITH 100µF 4.87k ITHM PLLLPF PGOOD TRACK MGN CLKOUT GND SGND VIN = 3.3V EFFICIENCY (%) VIN 2.7V TO 5.5V VOUT = 1.8V 90 VIN = 5V 85 80 PGOOD VOUT 4608A TA01a 75 70 0 2 4 6 LOAD CURRENT (A) 8 10 4608A TA01b 4608afc 1 LTM4608A ABSOLUTE MAXIMUM RATINGS (Note 1) VIN, SVIN....................................................... –0.3V to 6V CLKOUT........................................................ –0.3V to 2V PGOOD, PLLLPF, CLKIN, PHMODE, MODE.. –0.3V to VIN ITH, ITHM, RUN, FB, TRACK,MGN, BSEL....... –0.3V to VIN VOUT, SW....................................... –0.3V to (VIN + 0.3V) Internal Operating Temperature Range (Note 2)................................................... –55°C to 125°C Storage Temperature Range................... –55°C to 125°C PIN CONFIGURATION 1 VIN GND PHMODE MODE F G GND RUN SGND 2 CLKIN TOP VIEW C D E B A SW CLKOUT 3 PLLLPF 4 SVIN 5 ITHM TRACK PGOOD 6 BSEL 7 MGN 8 ITH FB 9 10 11 GND VOUT LGA PACKAGE 68-LEAD (15mm × 9mm × 2.8mm) TJMAX = 125°C, θJA = 25°C/W, θJCbottom = 7°C/W, θJCtop = 50°C/W, WEIGHT = 1.0g ORDER INFORMATION LEAD FREE FINISH TRAY PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTM4608AEV#PBF LTM4608AEV#PBF LTM4608AV 68-Lead (15mm × 9mm × 2.8mm) LGA –40°C to 125°C LTM4608AIV#PBF LTM4608AIV#PBF LTM4608AV 68-Lead (15mm × 9mm × 2.8mm) LGA –40°C to 125°C LTM4608AMPV#PBF LTM4608AMPV#PBF LTM4608AMPV 68-Lead (15mm × 9mm × 2.8mm) LGA –55°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ This product is only offered in trays. For more information go to: http://www.linear.com/packaging/ ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V unless otherwise noted. See Figure 1. SYMBOL PARAMETER VIN(DC) Input DC Voltage VOUT(DC) Output Voltage, Total Variation with Line and Load CONDITIONS CIN = 10µF × 1, COUT = 100µF Ceramic, 100µF POSCAP, RFB = 6.65k, MODE = 0V VIN = 2.7V to 5.5V, IOUT = IOUT(DC)MIN to IOUT(DC)MAX (Note 3) MIN l 2.7 l 1.472 1.464 2.05 1.85 TYP MAX UNITS 5.5 V 1.49 1.49 1.508 1.516 V V 2.2 2.0 2.35 2.15 V V Input Specifications VIN(UVLO) Undervoltage Lockout Threshold SVIN Rising SVIN Falling 4608afc 2 LTM4608A ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V unless otherwise noted. See Figure 1. SYMBOL PARAMETER CONDITIONS MIN IQ(VIN) Input Supply Bias Current VIN = 3.3V, No Switching, MODE = VIN VIN = 3.3V, No Switching, MODE = 0V VIN = 3.3V, VOUT = 1.5V, Switching Continuous 400 1.15 55 µA mA mA VIN = 5V, No Switching, MODE = VIN VIN = 5V, No Switching, MODE = 0V VIN = 5V, VOUT = 1.5V, Switching Continuous 450 1.3 75 µA mA mA 1 µA 4.5 2.93 A A Shutdown, RUN = 0, VIN = 5V IS(VIN) Input Supply Current VIN = 3.3V, VOUT = 1.5V, IOUT = 8A VIN = 5V, VOUT = 1.5V, IOUT = 8A TYP MAX UNITS Output Specifications IOUT(DC) Output Continuous Current Range VOUT = 1.5V (Note 3) VIN = 3.3V, 5.5V VIN = 2.7V ∆VOUT(LINE) Line Regulation Accuracy VOUT = 1.5V, VIN from 2.7V to 5.5V, IOUT = 0A l 0.1 0.25 %/V Load Regulation Accuracy VOUT = 1.5V (Note 3) VIN = 3.3V, 5.5V, ILOAD = 0A to 8A VIN = 2.7V, ILOAD = 0A to 5A l l 0.3 0.3 0.75 0.75 % % 0 0 8 5 A A VOUT ∆VOUT(LOAD) VOUT VOUT(AC) Output Ripple Voltage IOUT = 0A, COUT = 100µF X5R Ceramic, VIN = 5V, VOUT = 1.5V fS Switching Frequency IOUT = 8A, VIN = 5V, VOUT = 1.5V fSYNC SYNC Capture Range ∆VOUT(START) Turn-On Overshoot COUT = 100µF, VOUT = 1.5V, IOUT = 0A VIN = 3.3V VIN = 5V tSTART Turn-On Time COUT = 100µF, VOUT = 1.5V, VIN = 5V, IOUT = 1A Resistive Load, Track = VIN, ∆VOUT(LS) 10 1.25 1.5 0.75 mVP-P 1.75 MHz 2.25 MHz 10 10 mV mV 100 µs Peak Deviation for Dynamic Load Load: 0% to 50% to 0% of Full Load, COUT = 100µF Ceramic, 100µF POSCAP, VIN = 5V, VOUT = 1.5V 15 mV tSETTLE Settling Time for Dynamic Load Step Load: 0% to 50% to 0% of Full Load, VIN = 5V, VOUT = 1.5V, COUT = 100µF 10 µs IOUT(PK) Output Current Limit COUT = 100µF VIN = 2.7V, VOUT = 1.5V VIN = 3.3V, VOUT = 1.5V VIN = 5V, VOUT = 1.5V 8 11 13 A A A Voltage at FB Pin IOUT = 0A, VOUT = 1.5V, VIN = 2.7V to 5.5V Control Section VFB l SS Delay 0.590 0.587 Internal Soft-Start Delay IFB VRUN RUN Pin On/Off Threshold RUN Rising RUN Falling 1.4 1.3 0.596 0.596 0.602 0.606 V V 90 µs 0.2 µA 1.55 1.4 1.7 1.5 V V 4608afc 3 LTM4608A ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V unless otherwise noted. See Figure 1. SYMBOL PARAMETER CONDITIONS TRACK Tracking Threshold (Rising) Tracking Threshold (Falling) Tracking Disable Threshold RUN = VIN RUN = 0V RFBHI Resistor Between VOUT and FB Pins ∆VPGOOD PGOOD Range %Margining Output Voltage Margining Percentage MIN TYP MAX 0.57 0.18 VIN – 0.5 9.95 10 V V V 10.05 ±10 MGN = VIN, BSEL = 0V MGN = VIN, BSEL = VIN MGN = VIN, BSEL = Float MGN = 0V, BSEL = 0V MGN = 0V, BSEL = VIN MGN = 0V, BSEL = Float Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTM4608A is tested under pulsed load conditions such that TJ ≈ TA. The LTM4608AE is guaranteed to meet specifications from 0°C to 125°C internal temperature. Specifications over the –40°C to 125°C internal operating temperature range are assured by design, characterization and correlation with statistical process controls. UNITS 4 9 14 –4 –9 –14 5 10 15 –5 –10 –15 kΩ % 6 11 16 –6 –11 –16 % % % % % % The LTM4608AI is guaranteed over the –40°C to 125°C internal operating temperature range and the LTM4608AMP is tested and guaranteed over the full –55°C to 125°C internal operating temperature range. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. Note 3: See output current derating curves for different VIN, VOUT and TA. 4608afc 4 LTM4608A TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current Efficiency vs Load Current 100 CONTINUOUS MODE CONTINUOUS MODE 95 90 90 90 85 80 5VIN 1.2VOUT 5VIN 1.5VOUT 5VIN 1.8VOUT 5VIN 2.5VOUT 5VIN 3.3VOUT 70 0 2 4 LOAD CURRENT EFFICIENCY (%) 95 75 85 80 3.3VIN 1.2VOUT 3.3VIN 1.5VOUT 3.3VIN 1.8VOUT 3.3VIN 2.5VOUT 75 6 70 8 0 2 4 LOAD CURRENT 6 70 8 VOUT (V) 80 60 VOUT = 1.5V VOUT = 2.5V VOUT = 3.3V 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 LOAD CURRENT (A) 2.7VIN 1.0VOUT 2.7VIN 1.5VOUT 2.7VIN 1.8VOUT 0 4 3 2 5 LOAD CURRENT (A) 1 VIN to VOUT Step-Down Ratio 4.0 4.0 3.5 3.5 3.0 3.0 2.5 2.5 2.0 1.5 1.0 0.5 0 2 3 4 5 2.0 1.5 1.0 VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V IOUT = 8A VOUT = 1.2V VOUT = 1.5V 6 0 VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V IOUT = 6A VOUT = 1.2V VOUT = 1.5V 0.5 2 3 VIN (V) 4608A G04 4 5 6 VIN (V) 4608A G05 Supply Current vs VIN 7 6 4608A G03 VOUT (V) 90 40 80 VIN to VOUT Step-Down Ratio 100 50 85 4608A G02 Burst Mode Efficiency with 5V Input 70 CONTINUOUS MODE 75 4608A G01 EFFICIENCY (%) Efficiency vs Load Current 100 95 EFFICIENCY (%) EFFICIENCY (%) 100 Load Transient Response 4608A G06 Load Transient Response 1.6 ILOAD 1A/DIV SUPPLY CURRENT (mA) 1.4 1.2 VO = 1.2V PULSE-SKIPPING MODE 1 VOUT 20mV/DIV AC COUPLED VOUT 20mV/DIV AC COUPLED 0.8 0.6 VO = 1.2V BURST MODE 0.4 0.2 0 ILOAD 2A/DIV VIN 2V/DIV 2.5 3 3.5 4 4.5 INPUT VOLTAGE (V) 5 5.5 4608A G08 VIN = 5V 20µs/DIV VOUT = 3.3V, RFB = 2.21k 2A/µs STEP COUT = 100µF X5R C1 = 100pF, C3 = 22pF FROM FIGURE 18 4608A G09 VIN = 5V 20µs/DIV VOUT = 2.5V, RFB = 3.09k 2.5A/µs STEP COUT = 100µF X5R C1 = 120pF, C3 = 47pF FROM FIGURE 18 4608A G07 4608afc 5 LTM4608A TYPICAL PERFORMANCE CHARACTERISTICS Load Transient Response Load Transient Response Load Transient Response ILOAD 2A/DIV ILOAD 2A/DIV ILOAD 2A/DIV VOUT 20mV/DIV AC COUPLED VOUT 20mV/DIV AC COUPLED VOUT 20mV/DIV AC COUPLED 4608A G10 VIN = 5V 20µs/DIV VOUT = 1.8V, RFB = 4.87k 2.5A/µs STEP COUT = 100µF X5R C1 = NONE, C3 = NONE FROM FIGURE 18 4608A G11 VIN = 5V 20µs/DIV VOUT = 1.5V, RFB = 6.65k 2.5A/µs STEP COUT = 100µF X5R C1 = NONE, C3 = NONE FROM FIGURE 18 Start-Up 4608A G12 VIN = 5V 20µs/DIV VOUT = 1.2V, RFB = 10k 2.5A/µs STEP COUT = 2 × 100µF C1 = 100pF, C3 = NONE FROM FIGURE 18 VFB vs Temperature Load Regulation vs Current 602 0 600 VOUT 0.5V/DIV –0.1 VFB (mV) 598 VIN 2V/DIV LOAD REGULATION (%) VIN = 5.5V VIN = 3.3V 596 VIN = 2.7V 594 VIN = 5V 50µs/DIV VOUT = 1.5V COUT = 100µF NO LOAD AND 8A LOAD (DEFAULT 100µs SOFT-START) 4608A G13 592 –0.2 –0.3 –0.4 FC MODE VIN = 3.3V VOUT = 1.5V –0.5 590 –55 –25 5 65 35 TEMPERATURE (°C) 95 125 –0.6 2 0 4608A G14 4 6 LOAD CURRENT (A) 8 4608A G15 Short-Circuit Protection (2.5V Short, No Load) 2.5V Output Current Short-Circuit Protection (2.5V Short, 4A Load) 3.0 2V/DIV OUTPUT VOLTAGE (V) 2.5 2V/DIV 2.0 5A/DIV 1.5 VIN 5V/DIV 5V/DIV VOUT VIN VOUT IOUT LOAD 5A/DIV IOUT 1.0 VIN = 5V VOUT = 2.5V 0.5 0 0 5 10 15 OUTPUT CURRENT (A) 50µs/DIV 4608A G17 VIN = 5V VOUT = 2.5V 50µs/DIV 4608A G18 20 4608A G16 4608afc 6 LTM4608A PIN FUNCTIONS VIN (C1, C8, C9, D1, D3-D5, D7-D9 and E8): Power Input Pins. Apply input voltage between these pins and GND pins. Recommend placing input decoupling capacitance directly between VIN pins and GND pins. VOUT (C10-C11, D10-D11, E9-E11, F9-F11, G9-G11): Power Output Pins. Apply output load between these pins and GND pins. Recommend placing output decoupling capacitance directly between these pins and GND pins. See Table 1. GND (A1-A11, B1, B9-B11, F3, F7-F8, G1-G8): Power Ground Pins for Both Input and Output Returns. SVIN (F4): Signal Input Voltage. This pin is internally connected to VIN through a lowpass filter. SGND (E1): Signal Ground Pin. Return ground path for all analog and low power circuitry. Tie a single connection to GND in the application. MODE (B5): Mode Select Input. Tying this pin high enables Burst Mode operation. Tying this pin low enables forced continuous operation. Floating this pin or tying it to VIN/2 enables pulse-skipping operation. CLKIN (B3): External Synchronization Input to Phase Detector. This pin is internally terminated to SGND with a 50k resistor. The phase locked loop will force the internal top power PMOS turn on to be synchronized with the rising edge of the CLKIN signal. Connect this pin to SVIN to enable spread spectrum modulation. During external synchronization, make sure the PLLLPF pin is not tied to VIN or GND. PLLLPF (E3): Phase Locked Loop Lowpass Filter. An internal lowpass filter is tied to this pin. In spread spectrum mode, placing a capacitor here to SGND controls the slew rate from one frequency to the next. Alternatively, floating this pin allows normal running frequency at 1.5MHz, tying this pin to SVIN forces the part to run at 1.33 times its normal frequency (2MHz), tying it to ground forces the frequency to run at 0.67 times its normal frequency (1MHz). PHMODE (B4): Phase Selector Input. This pin determines the phase relationship between the internal oscillator and CLKOUT. Tie it high for 2-phase operation, tie it low for 3-phase operation, and float or tie it to VIN/2 for 4-phase operation. MGN (B8): Margining Pin. Increases or decreases the output voltage by the amount specified by the BSEL pin. To disable margining, tie the MGN pin to a voltage divider with 50k resistors from VIN to ground. See the Applications Information section and Figure 20. BSEL (B7): Margining Bit Select Pin. Tying BSEL low selects ±5%, tying it high selects ±10%. Floating it or tying it to VIN/2 selects ±15%. TRACK (E5): Output Voltage Tracking Pin. Voltage tracking is enabled when the TRACK voltage is below 0.57V. If tracking is not desired, then connect the TRACK pin to SVIN. If TRACK is not tied to SVIN, then the TRACK pin’s voltage needs to be below 0.18V before the chip shuts down even though RUN is already low. Do not float this pin. A resistor divider and capacitor can be applied to the TRACK pin to increase the soft-start time of the regulator. See the Applications Information section. Can tie together for parallel operation and tracking. Load current needs to be present during track down. 4608afc 7 LTM4608A PIN FUNCTIONS FB (E7): The Negative Input of the Error Amplifier. Internally, this pin is connected to VOUT with a 10k precision resistor. Different output voltages can be programmed with an additional resistor between FB and GND pins. In PolyPhase® operation, tie FB pins together for parallel operation. See the Applications Information section for details. ITH (F6): Current Control Threshold and Error Amplifier Compensation Point. The current comparator threshold increases with this control voltage. Tie together in parallel operation. ITHM (F5): Negative Input to the Internal ITH Differential Amplifier. Tie this pin to SGND for single phase operation. For PolyPhase operation, tie the master’s ITHM to SGND while connecting all of the ITHM pins together. PGOOD (C7): Output Voltage Power Good Indicator. Open-drain logic output that is pulled to ground when the output voltage is not within ±10% of the regulation point. Disabled during margining. RUN (F1): Run Control Pin. A voltage above 1.5V will turn on the module. SW (C3-C5): Switching Node of the Circuit is Used for Testing Purposes. This can be connected to an electrically open circuit copper pad on the board for improved thermal performance. CLKOUT (F2): Output Clock Signal for PolyPhase Operation. The phase of CLKOUT is determined by the state of the PHMODE pin. 4608afc 8 LTM4608A SIMPLIFIED BLOCK DIAGRAM SVIN VIN INTERNAL FILTER TRACK 10µF 10µF VIN 2.7 TO 5.5V + 10µF CIN MGN BSEL SW M1 PGOOD MODE 0.22µH POWER CONTROL RUN VOUT VOUT 1.5V CLKIN CLKOUT M2 PHMODE 22pF 22µF COUT GND ITH PLLLPF 10k INTERNAL COMP FB RFB 6.65k INTERNAL FILTER ITHM SGND 4608A BD Figure 1. Simplified LTM4608A Block Diagram Table 1. Decoupling Requirements. TA = 25°C, Block Diagram Configuration SYMBOL PARAMETER CONDITIONS CIN External Input Capacitor Requirement (VIN = 2.7V to 5.5V, VOUT = 1.5V) IOUT = 8A COUT External Output Capacitor Requirement (VIN = 2.7V to 5.5V, VOUT = 1.5V) IOUT = 8A MIN TYP 10 MAX UNITS µF 100 µF OPERATION The LTM4608A is a standalone nonisolated switch mode DC/DC power supply. It can deliver up to 8A of DC output current with few external input and output capacitors. This module provides precisely regulated output voltage programmable via one external resistor from 0.6V DC to 5.0V DC over a 2.7V to 5.5V input voltage. The typical application schematic is shown in Figure 18. The LTM4608A has an integrated constant frequency current mode regulator and built-in power MOSFET devices with fast switching speed. The typical switching frequency is 1.5MHz. For switching noise sensitive applications, it can be externally synchronized from 0.75MHz to 2.25MHz. Even spread spectrum switching can be implemented in the design to reduce noise. 4608afc 9 LTM4608A OPERATION With current mode control and internal feedback loop compensation, the LTM4608A module has sufficient stability margins and good transient performance with a wide range of output capacitors, even with all ceramic output capacitors. conditions. The Linear Technology µModule Power Design Tool is provided for transient and stability analysis. The FB pin is used to program the output voltage with a single external resistor to ground. Current mode control provides cycle-by-cycle fast current limit and thermal shutdown in an overcurrent condition. Internal overvoltage and undervoltage comparators pull the open-drain PGOOD output low if the output feedback voltage exits a ±10% window around the regulation point. Multiphase operation can be easily employed with the synchronization and phase mode controls. Up to 12 phases can be cascaded to run simultaneously with respect to each other by programming the PHMODE pin to different levels. The LTM4608A has clock in and clock out for poly phasing multiple devices or frequency synchronization. Pulling the RUN pin below 1.3V forces the controller into its shutdown state, by turning off both M1 and M2 at low load current. The TRACK pin is used for programming the output voltage ramp and voltage tracking during start-up. See Applications Information. High efficiency at light loads can be accomplished with selectable Burst Mode operation using the MODE pin. These light load features will accommodate battery operation. Efficiency graphs are provided for light load operation in the Typical Performance Characteristics. The LTM4608A is internally compensated to be stable over all operating conditions. Table 3 provides a guideline for input and output capacitances for several operating Output voltage margining is supported, and can be programed from ±5% to ±15% using the MGN and BSEL pins. The PGOOD pin is disabled during margining APPLICATIONS INFORMATION The typical LTM4608A application circuit is shown in Figure 18. External component selection is primarily determined by the maximum load current and output voltage. Refer to Table 3 for specific external capacitor requirements for a particular application. no feedback resistor. Adding a resistor RFB from FB pin to GND programs the output voltage: VIN to VOUT Step-Down Ratios Table 2. RFB Resistor vs Output Voltage There are restrictions in the maximum VIN to VOUT stepdown ratio that can be achieved for a given input voltage. The LTM4608A is 100% duty cycle, but the VIN to VOUT minimum dropout is a function of its load current. Please refer to the curves in the Typical Performance Characteristics section of this data sheet for more information. Output Voltage Programming The PWM controller has an internal 0.596V reference voltage. As shown in the Block Diagram, a 10k 0.5% internal feedback resistor connects VOUT and FB pins together. The output voltage will default to 0.596V with VOUT = 0.596V • 10k + RFB RFB VOUT 0.596V 1.2V 1.5V 1.8V 2.5V 3.3V RFB Open 10k 6.65k 4.87k 3.09k 2.21k Input Capacitors The LTM4608A module should be connected to a low AC impedance DC source. Three 10µF ceramic capacitors are included inside the module. Additional input capacitors are only needed if a large load step is required up to the 4A level. A 47µF to 100µF surface mount aluminum electrolytic bulk capacitor can be used for more input bulk capacitance. This bulk input capacitor is only needed if the input source impedance is compromised by long inductive leads, traces or not enough source capacitance. 4608afc 10 LTM4608A APPLICATIONS INFORMATION If low impedance power planes are used, then this 47µF capacitor is not needed. For a buck converter, the switching duty-cycle can be estimated as: D= VOUT VIN Burst Mode Operation Without considering the inductor current ripple, the RMS current of the input capacitor can be estimated as: ICIN(RMS) = a function of stability and transient response. The Linear Technology LTpowerCAD Design Tool will calculate the output ripple reduction as the number phases implemented increases by N times. IOUT(MAX) η% • D • (1– D) In the above equation, η% is the estimated efficiency of the power module. The bulk capacitor can be a switcherrated electrolytic aluminum capacitor, polymer capacitor for bulk input capacitance due to high inductance traces or leads. If a low inductance plane is used to power the device, then only one 10µF ceramic is required. The three internal 10µF ceramics are typically rated for 2A of RMS ripple current, so the ripple current at the worse case for 8A maximum current is 4A or less. Output Capacitors The LTM4608A is designed for low output voltage ripple noise. The bulk output capacitors defined as COUT are chosen with low enough effective series resistance (ESR) to meet the output voltage ripple and transient requirements. COUT can be a low ESR tantalum capacitor, a low ESR polymer capacitor or ceramic capacitor. The typical output capacitance range is from 47µF to 220µF. Additional output filtering may be required by the system designer, if further reduction of output ripple or dynamic transient spikes is desired. Table 3 shows a matrix of different output voltages and output capacitors to minimize the voltage droop and overshoot during a 3A/µs transient. The table optimizes total equivalent ESR and total bulk capacitance to optimize the transient performance. Stability criteria are considered in the Table 3 matrix, and the Linear Technology LTpowerCAD™ Design Tool is available for stability analysis. Multiphase operation will reduce effective output ripple as a function of the number of phases. Application Note 77 discusses this noise reduction versus output ripple current cancellation, but the output capacitance will be more The LTM4608A is capable of Burst Mode operation in which the power MOSFETs operate intermittently based on load demand, thus saving quiescent current. For applications where maximizing the efficiency at very light loads is a high priority, Burst Mode operation should be applied. To enable Burst Mode operation, simply tie the MODE pin to VIN. During this operation, the peak current of the inductor is set to approximately 20% of the maximum peak current value in normal operation even though the voltage at the ITH pin indicates a lower value. The voltage at the ITH pin drops when the inductor’s average current is greater than the load requirement. As the ITH voltage drops below 0.2V, the BURST comparator trips, causing the internal sleep line to go high and turn off both power MOSFETs. In sleep mode, the internal circuitry is partially turned off, reducing the quiescent current to about 450µA. The load current is now being supplied from the output capacitor. When the output voltage drops, causing ITH to rise above 0.25V, the internal sleep line goes low, and the LTM4608A resumes normal operation. The next oscillator cycle will turn on the top power MOSFET and the switching cycle repeats. Pulse-Skipping Mode Operation In applications where low output ripple and high efficiency at intermediate currents are desired, pulse-skipping mode should be used. Pulse-skipping operation allows the LTM4608A to skip cycles at low output loads, thus increasing efficiency by reducing switching loss. Floating the MODE pin or tying it to VIN/2 enables pulse-skipping operation. This allows discontinuous conduction mode (DCM) operation down to near the limit defined by the chip’s minimum on-time (about 100ns). Below this output current level, the converter will begin to skip cycles in order to maintain output regulation. Increasing the output load current slightly, above the minimum required for discontinuous conduction mode, allows constant frequency PWM. 4608afc 11 LTM4608A APPLICATIONS INFORMATION Table 3. Output Voltage Response Versus Component Matrix (Refer to Figure 18) 0A to 3A Load Step TYPICAL MEASURED VALUES VALUE COUT1 VENDORS TDK 22µF, 6.3V Murata 22µF, 16V TDK 100µF, 6.3V Murata 100µF, 6.3V VOUT (V) 1.0 1.0 1.0 1.0 1.0 1.0 1.2 1.2 1.2 1.2 1.2 1.2 1.5 1.5 1.5 1.5 1.5 1.5 1.8 1.8 CIN (CERAMIC) 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF 10µF CIN (BULK)* 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF 100µF PART NUMBER C3216X7S0J226M GRM31CR61C226KE15L C4532X5R0J107MZ GRM32ER60J107M COUT1 (CERAMIC) 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 2 22µF × 1 100µF × 1 22µF × 1 COUT2 (BULK) COUT2 VENDORS Sanyo POSCAP CIN (BULK) VENDORS Sanyo VALUE 150µF, 10V VALUE 100µF, 10V PART NUMBER 10TPD150M PART NUMBER 10CE100FH ITH None None None None None None None None None None None None None None None None None None None None C1 68pF None 68pF None 68pF None 100pF None 100pF None 100pF 47pF 100pF None 100pF None 100pF None 47pF None C3 None 100pF None 100pF None 100pF None 100pF None 100pF None None None 47pF None 47pF None None None 47pF VIN (V) 5 5 3.3 3.3 2.7 2.7 5 5 3.3 3.3 2.7 2.7 5 5 3.3 3.3 2.7 2.7 5 5 DROOP (mV) 13 17 13 17 13 17 16 20 16 20 16 16 18 20 16 20 18 20 22 21 PEAK-TO- PEAK DEVIATION (mV) 26 34 26 34 26 34 32 41 32 41 32 32 36 41 32 41 36 41 42 42 RECOVERY TIME (µs) 7 8 7 10 7 8 8 10 8 10 10 8 8 12 10 12 10 12 8 12 LOAD STEP (A/µs) 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 RFB (kΩ) 14.7 14.7 14.7 14.7 14.7 14.7 10 10 10 10 10 10 6.65 6.65 6.65 6.65 6.65 6.65 4.87 4.87 1.8 10µF 100µF 100µF × 2 None 1.8 10µF 100µF 22µF × 1 150µF × 2 None 1.8 10µF 100µF 100µF × 2 None 1.8 10µF 100µF 22µF × 1 150µF × 2 None 2.5 10µF 100µF 100µF × 1 None 2.5 10µF 100µF 22µF × 1 150µF × 1 None 2.5 10µF 100µF 100µF × 1 None 2.5 10µF 100µF 22µF × 1 150µF × 1 None 3.3 10µF 100µF 100µF × 1 100pF 3.3 10µF 100µF 22µF × 1 150µF × 1 None *Bulk capacitance is optional if VIN has very low input impedance. 120pF None 120pF None 100pF 22pF 100pF 22pF 22pF None None 47pF None None None None None None None None 3.3 3.3 2.7 2.7 5 5 3.3 3.3 5 5 21 21 22 21 28 33 30 21 38 39 43 41 44 42 42 60 60 41 74 75 12 12 12 14 10 10 10 10 10 12 3 3 3 3 3 3 3 3 3 3 4.87 4.87 4.87 4.87 3.09 3.09 3.09 3.09 2.21 2.21 150µF × 2 150µF × 2 150µF × 2 150µF × 2 150µF × 2 150µF × 2 150µF × 2 150µF × 2 150µF × 2 150µF × 2 Forced Continuous Operation In applications where fixed frequency operation is more critical than low current efficiency, and where the lowest output ripple is desired, forced continuous operation should be used. Forced continuous operation can be enabled by tying the MODE pin to GND. In this mode, inductor current is allowed to reverse during low output loads, the ITH voltage is in control of the current comparator threshold throughout, and the top MOSFET always turns on with each oscillator pulse. During start-up, forced continuous mode is disabled and inductor current is prevented from reversing until the LTM4608A’s output voltage is in regulation. Multiphase Operation For output loads that demand more than 8A of current, multiple LTM4608As can be cascaded to run out of phase to 4608afc 12 LTM4608A APPLICATIONS INFORMATION provide more output current without increasing input and output voltage ripple. The CLKIN pin allows the LTM4608A to synchronize to an external clock (between 0.75MHz and 2.25MHz) and the internal phase locked loop allows the LTM4608A to lock onto CLKIN’s phase as well. The CLKOUT signal can be connected to the CLKIN pin of the following LTM4608A stage to line up both the frequency and the phase of the entire system. Tying the PHMODE pin to SVIN, SGND or SVIN/2 (floating) generates a phase difference (between CLKIN and CLKOUT) of 180°, 120° or 90° respectively, which corresponds to a 2-phase, 3-phase or 4-phase operation. A total of 6 phases can be cascaded to run simultaneously with respect to each other by programming the PHMODE pin of each LTM4608A to different levels. For a 6-phase example in Figure 2, the 2nd stage that is 120° out of phase from the 1st stage can generate a 240° (PHMODE = 0) CLKOUT signal for 0 CLKIN CLKOUT 120 +120 PHMODE PHASE 1 A multiphase power supply significantly reduces the amount of ripple current in both the input and output capacitors. The RMS input ripple current is reduced by, and the effective ripple frequency is multiplied by, the number of phases used (assuming that the input voltage is greater than the number of phases used times the output voltage). The output ripple amplitude is also reduced by the number of phases used. (420) 60 240 CLKIN CLKOUT PHMODE the 3rd stage, which then can generate a CLKOUT signal that’s 420°, or 60° (PHMODE = SVIN) for the 4th stage. With the 60° CLKIN input, the next two stages can shift 120° (PHMODE = 0) for each to generate a 300° signal for the 6th stage. Finally, the signal with a 60° phase shift on the 6th stage (PHMODE is floating) goes back to the 1st stage. Figure 3 shows the configuration for 12-phase operation. +120 SVIN CLKIN CLKOUT +180 PHMODE CLKIN CLKOUT PHMODE PHASE 5 PHASE 3 180 +120 300 CLKIN CLKOUT +120 PHMODE PHMODE PHASE 4 PHASE 2 CLKIN CLKOUT 4608A F02 PHASE 6 Figure 2. 6-Phase Operation 0 CLKIN CLKOUT 120 +120 PHMODE V+ OUT1 (420) 60 240 CLKIN CLKOUT PHMODE +120 SVIN CLKIN CLKOUT +180 PHMODE CLKIN CLKOUT PHMODE CLKIN CLKOUT 300 +120 PHMODE CLKIN CLKOUT PHMODE 4608 F02 PHASE 1 PHASE 5 PHASE 9 PHASE 3 PHASE 7 PHASE 11 90 210 330 (510) 150 270 (390) 30 LTC6908-2 OUT2 180 +120 CLKIN CLKOUT PHMODE PHASE 4 +120 CLKIN CLKOUT PHMODE PHASE 8 +120 SVIN CLKIN CLKOUT PHMODE +180 CLKIN CLKOUT PHMODE PHASE 12 PHASE 6 +120 CLKIN CLKOUT PHMODE PHASE 10 +120 CLKIN CLKOUT PHMODE 4608A F03 PHASE 2 Figure 3. 12-Phase Operation 4608afc 13 LTM4608A APPLICATIONS INFORMATION The LTM4608A device is an inherently current mode controlled device. Parallel modules will have very good current sharing. This will balance the thermals on the design. Tie the ITH pins of each LTM4608A together to share the current evenly. To reduce ground potential noise, tie the ITHM pins of all LTM4608As together and then connect to the SGND at only one point. Figure 19 shows a schematic of the parallel design. The FB pins of the parallel module are tied together. With parallel operation, input and output capacitors may be reduced in part according to the operating duty cycle. Input RMS Ripple Current Cancellation Application Note 77 provides a detailed explanation of multiphase operation. The input RMS ripple current cancellation mathematical derivations are presented, and a graph is displayed representing the RMS ripple current reduction as a function of the number of interleaved phases. Figure 4 shows this graph. Spread Spectrum Operation Switching regulators can be particularly troublesome where electromagnetic interference (EMI) is concerned. Switching regulators operate on a cycle-by-cycle basis to transfer power to an output. In most cases, the frequency of operation is fixed based on the output load. This method of conversion creates large components of noise at the frequency of operation (fundamental) and multiples of the operating frequency (harmonics). To reduce this noise, the LTM4608A can run in spread spectrum operation by tying the CLKIN pin to SVIN. In spread spectrum operation, the LTM4608A’s internal oscillator is designed to produce a clock pulse whose period is random on a cycle-by-cycle basis but fixed between 70% and 130% of the nominal frequency. This has the benefit of spreading the switching noise over a range of frequencies, thus significantly reducing the peak noise. Spread spectrum operation is disabled if 0.60 1-PHASE 2-PHASE 3-PHASE 4-PHASE 6-PHASE 0.55 0.50 RMS INPUT RIPPLE CURRENT DC LOAD CURRENT 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 DUTY FACTOR (VO/VIN) 4608A F04 Figure 4. Normalized Input RMS Ripple Current vs Duty Factor for One to Six Phases 4608afc 14 LTM4608A APPLICATIONS INFORMATION CLKIN is tied to ground or if it’s driven by an external frequency synchronization signal. A capacitor value of 0.01µF must be placed from the PLLLPF pin to ground to control the slew rate of the spread spectrum frequency change. Add a control ramp on the TRACK pin with RSR and CSR referenced to VIN. Figure 21 shows an example for spread spectrum operation. 1 RSR ≥ 0.592 − ln 1− • 500 • C SR VIN Output Voltage Tracking Output voltage tracking can be programmed externally using the TRACK pin. The output can be tracked up and down with another regulator. The master regulator’s output is divided down with an external resistor divider that is the VIN 5V same as the slave regulator’s feedback divider to implement coincident tracking. The LTM4608A uses an accurate 10k resistor internally for the top feedback resistor. Figure 5 shows an example of coincident tracking: 10k Slave = 1+ • VTRACK R FB4 VTRACK is the track ramp applied to the slave’s track pin. VTRACK has a control range of 0V to 0.596V, or the internal reference voltage. When the master’s output is divided down with the same resistor values used to set the slave’s output, this resistor divider is connected to the slave’s track pin. The slave will then coincident track with the master until it reaches its final value. The master will continue to its final value from the slave’s regulation point. Voltage tracking is disabled when VTRACK is more than 0.596V. CLKIN VIN VOUT SVIN TIE TO VIN FOR DISABLE AND DEFAULT 100µs SOFT-START RSR SW RUN TRACK CSR RUN LTM4608A C2 100pF FB ITH PLLLPF ITHM TRACK PGOOD MODE BSEL RFB1 2.21k 100µF C3 22pF VIN 50k PHMODE MGN APPLY A CONTROL CLKOUT GND SGND RAMP WITH RSR AND CSR TIED TO VIN WHERE t = –(ln (1 – 0.596/VIN) • RSR • CSR) OR APPLY AN EXTERNAL TRACKING RAMP CLKIN VIN 50k VOUT C1 100µF SVIN MASTER 3.3V RFB3 10k RFB4 6.65k SW RUN TRACK RUN LTM4608A MASTER 3.3V 7A + C4 100µF SLAVE 1.5V 8A FB ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN RFB2 6.65k CLKOUT GND SGND 4608A F05 Figure 5. Dual Outputs (3.3V and 1.5V) with Tracking 4608afc 15 LTM4608A APPLICATIONS INFORMATION 0.596V t = – ln 1– • RSR • CSR VIN Ratiometric tracking can be achieved by a few simple calculations and the slew rate value applied to the master’s track pin. As mentioned above, the TRACK pin has a control range from 0V to 0.596V. The master’s TRACK pin slew rate is directly equal to the master’s output slew rate in Volts/Time: MR • 10k = RFB3 SR where MR is the master’s output slew rate and SR is the slave’s output slew rate in Volts/Time. When coincident tracking is desired, then MR and SR are equal, thus RFB3 is equal the 10k. RFB4 is derived from equation: RFB4 = 0.596V VFB VFB VTRACK + – 10k RFB2 RFB3 where VFB is the feedback voltage reference of the regulator and VTRACK is 0.596V. Since RFB3 is equal to the 10k top feedback resistor of the slave regulator in equal slew rate or coincident tracking, then RFB4 is equal to RFB2 with VFB = VTRACK. Therefore RFB3 = 10k and RFB4 = 6.65k in Figure 5. In ratiometric tracking, a different slew rate maybe desired for the slave regulator. RFB3 can be solved for when SR is slower than MR. Make sure that the slave supply slew rate is chosen to be fast enough so that the slave output voltage will reach it final value before the master output. MASTER OUTPUT OUTPUT VOLTAGE (V) The track pin of the master can be controlled by an external ramp or by RSR and CSR in Figure 5 referenced to VIN. The RC ramp time can be programmed using equation: SLAVE OUTPUT TIME 4608A F06 Figure 6. Output Voltage Coincident Tracking For example: MR = 3.3V/ms and SR = 1.5V/ms. Then RFB3 = 22.1k. Solve for RFB4 to equal to 4.87k. For applications that do not require tracking or sequencing, simply tie the TRACK pin to SVIN to let RUN control the turn on/off. Connecting TRACK to SVIN also enables the ~100µs of internal soft-start during start-up. Load current needs to be present during track down. Power Good The PGOOD pin is an open-drain pin that can be used to monitor valid output voltage regulation. This pin monitors a ±10% window around the regulation point. As shown in Figure 20, the sequencing function can be realized in a dual output application by controlling the RUN pins and the PGOOD signals from each other. The 1.5V output begins its soft starting after the PGOOD signal of 3.3V output becomes high, and 3.3V output starts its shut down after the PGOOD signal of 1.5V output becomes low. This can be applied to systems that require voltage sequencing between the core and sub-power supplies. 4608afc 16 LTM4608A APPLICATIONS INFORMATION Slope Compensation The module has already been internally compensated for all output voltages. Table 3 is provided for most application requirements. A spice model will be provided for other control loop optimization. For single module operation, connect ITHM pin to SGND. For parallel operation, tie ITHM pins together and then connect to SGND at one point. Tie ITH pins together to share currents evenly for all phases. Output Margining Thermal Considerations and Output Current Derating The power loss curves in Figures 7 and 8 can be used in coordination with the load current derating curves in Figures 9 to 16 for calculating an approximate θJA for the module with various heat sinking methods. Thermal models are derived from several temperature measurements at the bench, and thermal modeling analysis. Thermal Application Note 103 provides a detailed explanation of the analysis for the thermal models and the derating curves. Tables 4 and 5 provide a summary of the equivalent θJA for the noted conditions. These equivalent θJA parameters are correlated to the measured values and improve with air flow. The junction temperature is maintained at 125°C or below for the derating curves. 4.0 4.0 3.5 3.5 3.0 3.0 POWER LOSS (W) POWER LOSS (W) For a convenient system stress test on the LTM4608A’s output, the user can program the LTM4608A’s output to ±5%, ±10% or ±15% of its normal operational voltage. The margin pin with a voltage divider is driven with a small three-state gate as shown in Figure 18, for the three margin states (high, low, no margin). When the MGN pin is < 0.3V, it forces negative margining in which the output voltage is below the regulation point. When MGN is >VIN – 0.3V, the output voltage is forced above the regulation point. The amount of output voltage margining is determined by the BSEL pin. When BSEL is low, it is 5%. When BSEL is high, it is 10%. When BSEL is floating, it is 15%. When margining is active, the internal output overvoltage and undervoltage comparators are disabled and PGOOD remains high. Margining is disabled by tying the MGN pin to a voltage divider as shown in Figure 20. 2.5 2.0 1.5 2.0 1.5 1.0 1.0 0.5 0 2.5 0.5 3.3VIN 1.5VOUT 3.3VIN 2.5VOUT 0 2 4 6 8 0 5VIN 1.5VOUT 5VIN 3.3VOUT 0 2 4 6 8 LOAD CURRENT (A) LOAD CURRENT (A) 4608A F07 Figure 7. 3.3VIN, 2.5V and 1.5VOUT Power Loss 4608A F08 Figure 8. 5VIN, 3.3V and 1.5VOUT Power Loss 4608afc 17 LTM4608A 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) APPLICATIONS INFORMATION 6 5 4 3 2 0 40 50 5 4 3 2 400LFM 200LFM 0LFM 1 6 400LFM 200LFM 0LFM 1 0 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608A F10 4608A F09 Figure 10. BGA Heat Sink with 3.3VIN to 1.5VOUT 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) Figure 9. No Heat Sink with 3.3VIN to 1.5VOUT 6 5 4 3 2 0 40 50 5 4 3 2 400LFM 200LFM 0LFM 1 6 400LFM 200LFM 0LFM 1 0 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608A F12 4608A F11 Figure 12. BGA Heat Sink with 5VIN to 1.5VOUT 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) Figure 11. No Heat Sink with 5VIN to 1.5VOUT 6 5 4 3 2 0 40 50 5 4 3 2 400LFM 200LFM 0LFM 1 6 400LFM 200LFM 0LFM 1 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608A F13 Figure 13. No Heat Sink with 3.3VIN to 2.5VOUT 0 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608A F14 Figure 14. BGA Heat Sink with 3.3VIN to 2.5VOUT 4608afc 18 LTM4608A 9 9 8 8 7 7 LOAD CURRENT (A) LOAD CURRENT (A) APPLICATIONS INFORMATION 6 5 4 3 2 0 40 50 5 4 3 2 400LFM 200LFM 0LFM 1 6 400LFM 200LFM 0LFM 1 0 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 40 50 60 70 80 90 100 110 120 AMBIENT TEMPERATURE (°C) 4608A F15 4608A F16 Figure 15. No Heat Sink with 5VIN to 3.3VOUT Figure 16. BGA Heat Sink with 5VIN to 3.3VOUT Table 4. 1.5V Output DERATING CURVE VIN (V) POWER LOSS CURVE AIR FLOW (LFM) HEAT SINK qJA (°C/W) Figures 9, 11 3.3, 5 Figures 9, 11 3.3, 5 Figures 7, 8 0 None 25 Figures 7, 8 200 None 21 Figures 9, 11 3.3, 5 Figures 7, 8 400 None 20 Figures 10, 12 3.3, 5 Figures 7, 8 0 BGA Heat Sink 23.5 Figures 10, 12 3.3, 5 Figures 7, 8 200 BGA Heat Sink 22 Figures 10, 12 3.3, 5 Figures 7, 8 400 BGA Heat Sink 22 DERATING CURVE VIN (V) POWER LOSS CURVE AIR FLOW (LFM) HEAT SINK qJA (°C/W) Figure 15 5 Figure 8 0 None 25 Figure 15 5 Figure 8 200 None 21 Table 5. 3.3V Output Figure 15 5 Figure 8 400 None 20 Figure 16 5 Figure 8 0 BGA Heat Sink 23.5 Figure 16 5 Figure 8 200 BGA Heat Sink 22 Figure 16 5 Figure 8 400 BGA Heat Sink 22 4608afc 19 LTM4608A APPLICATIONS INFORMATION Safety Considerations The LTM4608A 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 LTM4608A 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 top layer and other power layers. • Do not put vias directly on the pads, unless they are capped. • Use a separated SGND ground copper area for components connected to signal pins. Connect the SGND to GND underneath the unit. Figure 17 gives a good example of the recommended layout. GND VOUT COUT COUT COUT GND CIN VIN CIN GND 4608A F17 Figure 17. Recommended PCB Layout 4608afc 20 LTM4608A TYPICAL APPLICATIONS CLKIN VIN 3V TO 5.5V CLKIN VIN CIN 10µF VOUT C1 220pF SVIN SW RUN MODE PHMODE FB LTM4608A RFB 3.09k ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN VOUT 2.5V 8A 8A AT 5V INPUT 6A AT 3.3V INPUT COUT 100µF C3 47pF VIN 100k PGOOD VIN (HIGH = 10%) (FLOAT = 15%) (LOW = 5%) 1 50k YOUT 4 5 2 U1 U1: PERICOM PI74ST1G126CEX 3 OR TOSHIBA TC7SZ126AFE BSEL CLKOUT GND SGND 50k OE AIN 4608A F18 OE AIN YOUT MGN H H L H L X MARGIN VALUE H + OF BSEL SELECTION L – OF BSEL SELECTION NO MARGIN VIN/2 H L Z Figure 18. Typical 3V to 5.5VIN, 2.5V at 8A Design VIN 3V TO 5.5V CLKIN VIN 10µF TRACK C4 100pF SVIN SW RUN VOUT RUN LTM4608A 100µF 6.3V X5R FB 3.32k ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN C3 100µF 6.3V X5R CLKOUT GND SGND C2 10µF CLKIN VIN VOUT C1 100µF 6.3V X5R SVIN SW RUN LTM4608A FB ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN VOUT 1.5V 16A VIN 50k 50k CLKOUT GND SGND 4608A F19 Figure 19. Two LTM4608As in Parallel, 1.5V at 16A Design. See Also Dual 8A per Channel LTM4616 4608afc 21 LTM4608A TYPICAL APPLICATIONS CLKIN VIN 5V CLKIN VIN VOUT SW SHDN RUN LTM4608A FB C3 22pF ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN 100k CLKOUT GND SGND R1 100k 100µF 6.3V X5R C2 100pF SVIN D1 MMSD4148 R2 100k RFB1 2.21k VIN SHDN 50k 3.3V 50k CLKIN VIN VOUT SVIN D2 MMSD4148 SW SHDN RUN FB LTM4608A RFB2 6.65k ITH ITHM PLLLPF VOUT2 3.3V 7A C1 100µF 6.3V X5R 1.5V + C4 100µF SANYO POSCAP 10mΩ VOUT1 1.5V 8A 100k TRACK PGOOD MODE BSEL PHMODE MGN CLKOUT GND SGND 4608A F20 Figure 20. Dual LTM4608A Output Sequencing Application. See Also Dual 8A per Channel LTM4616 SVIN VIN 2.7V TO 5.5V 0.01µF CLKIN VIN CSR 0.22µF 10µF SVIN RSR 180k SW MODE PHMODE RUN VOUT 100pF LTM4608A FB 10k ITH PLLLPF ITHM TRACK PGOOD MODE BSEL PHMODE MGN CLKOUT GND SGND PGOOD BSEL 4608A F21 C2 100µF 6.3V X5R C1 100µF 6.3V X5R VOUT 1.2V/8A 5A AT 2.7V INPUT VIN 50k 50k Figure 21. 2.7V to 5.5VIN, 1.2VOUT Design in Spread Spectrum Operation 4608afc 22 VIN 5V R5 3.09k R4 10k 3.3V TRACK OR RAMP CONTROL BSEL MGN MODE PHMODE MGN PHMODE C8 47pF C4 22pF R2 3.09k C7 220pF 50k 50k VIN R10 2.21k C2 100pF C1 100µF 6.3V X5R VOUT2 2.5V 8A VOUT1 3.3V 100µF 7A 6.3V X5R R7 6.65k R6 10k 3.3V R9 4.87k R8 10k 3.3V MGN PHMODE MGN BSEL PGOOD ITHM ITH FB VOUT CLKOUT GND SGND PHMODE MODE TRACK CLKIN LTM4608A PLLLPF RUN SW SVIN VIN CLKOUT GND SGND BSEL MODE ITHM PGOOD ITH FB VOUT TRACK LTM4608A CLKIN PLLLPF RUN SW SVIN VIN Figure 22. 4-Phase, Four Outputs (3.3V, 2.5V, 1.8V and 1.5V) with Tracking BSEL MODE CLKOUT GND SGND PGOOD TRACK ITH FB VOUT ITHM LTM4608A CLKIN PLLLPF RUN SW SVIN VIN CLKOUT GND SGND ITHM PGOOD ITH FB VOUT TRACK LTM4608A CLKIN PLLLPF RUN SW SVIN VIN CLKIN 4608A F22 R8 6.65k R1 4.87k C8 100pF C5 100µF 6.3V X5R + C3 100µF 6.3V X5R C9 100µF 6.3V SANYO POSCAP 10mΩ VOUT4 1.5V 8A VOUT3 1.8V 8A LTM4608A TYPICAL APPLICATIONS 4608afc 23 LTM4608A PACKAGE DESCRIPTION LGA Package 68-Lead (15mm × 9mm × 2.82mm) (Reference LTC DWG # 05-08-1821 Rev Ø) DETAIL A 2.72 – 2.92 G aaa Z F E D C B PAD 1 A 1 PAD “A1” CORNER 2 4 3 4 5 15.00 BSC MOLD CAP 12.70 BSC SUBSTRATE 6 7 0.290 – 0.350 2.200 – 2.600 8 9 Z // bbb Z DETAIL B 10 11 9.00 BSC aaa Z 0.630 ±0.025 SQ. 68x X eee S X Y Y DETAIL B PADS SEE NOTES 3 PACKAGE BOTTOM VIEW 3.810 2.540 1.270 0.000 1.270 2.540 PACKAGE TOP VIEW 3.810 7.620 BSC 1.27 BSC DETAIL A 6.350 5.080 3.810 2.540 1.270 0.000 1.270 2.540 3.810 5.080 6.350 NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 2. ALL DIMENSIONS ARE IN MILLIMETERS 3 LAND DESIGNATION PER JESD MO-222 4 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: 68 SYMBOL TOLERANCE aaa 0.15 bbb 0.10 eee 0.05 COMPONENT PIN “A1” TRAY PIN 1 BEVEL LTMXXXXXX µModule PACKAGE IN TRAY LOADING ORIENTATION LGA 68 1207 REV Ø SUGGESTED PCB LAYOUT TOP VIEW PACKAGE PHOTO 4608afc 24 LTM4608A REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 12/10 Voltage changed in the Typical Application drawing. 1 Changes made to the Absolute Maximum Ratings section. 2 Updated the Pin Configuration package dimensions. 2 Changes made to the VOUT conditions in the Electrical Characteristics section. 2 Updated Note 2 in the Electrical Characteristics section. 4 Replaced graphs G05 and G06 in the Typical Performance Characteristics section. 5 Updated MGN (B8) in the Pin Functions section. C 3/11 7 Text changes made to the Applications Information section. 10, 11, 14, 19 Changes made to Figures 5, 18, 20, 21, 23. 15, 21, 22, 23 Updated the Related Parts table. 26 Updated Pin Configuration drawing 2 Removed Pin Configuration drawing from Pin Functions 8 Added value of 0.22µH to Inductor in Figure 1 9 Updated Figure 3 13 Updated Figure 17 20 Added Package Photo 24 4608afc 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. 25 LTM4608A PACKAGE DESCRIPTION Pin Assignment Table (Arranged by Pin Number) PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME A1GND B1GND C1VIN D1VIN E1SGND F1RUN G1GND A2GND B2– C2– D2– E2– F2CLKOUT G2GND A3GND B3CLKIN C3SW D3VIN E3PLLLPF F3GND G3GND A4GND B4PHMODE C4SW D4VIN E4– F4SVIN G4GND A5GND B5MODE C5SW D5VIN E5TRACK F5ITHM G5GND A6GND B6– C6– D6– E6– F6ITH G6GND A7GND B7BSEL C7PGOOD D7VIN E7FB F7GND G7GND A8GND B8MGN C8VIN D8VIN E8VIN F8GND G8GND A9GND B9GND C9VIN D9VIN E9VOUT F9VOUT G9VOUT A10GND B10GND C10VOUT D10VOUT E10VOUT F10VOUT G10VOUT A11GND B11GND C11VOUT D11VOUT E11VOUT F11VOUT G11VOUT RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC2900 Quad Supply Monitor with Adjustable Reset Timer Monitors Four Supplies; Adjustable Reset Timer LTC2923 Power Supply Tracking Controller Tracks Both Up and Down; Power Supply Sequencing LTM4600HV 10A DC/DC µModule Regulator 4.5V ≤ VIN ≤ 28V; 0.6V ≤ VOUT ≤ 5V, LGA Package LTM4600HVMP Military Plastic 10A DC/DC µModule Regulator Guaranteed Operation from –55°C to 125°C Ambient, LGA Package LTM4601/ LTM4601A 12A DC/DC µModule Regulator with PLL, Output Tracking/ Margining and Remote Sensing Synchronizable, PolyPhase Operation, LTM4601-1/LTM4601A-1 Version Has No Remote Sensing, LGA Package, MP Version Available LTM4602 6A DC/DC µModule Regulator Pin Compatible with the LTM4600, LGA Package LTM4618 6A DC/DC µModule Regulator with PLL and Output Tracking/Margining and Remote Sensing Synchronizable, PolyPhase Operation LTM4604A Low VIN 4A DC/DC µModule Regulator 2.375V ≤ VIN ≤ 5.5V, 0.8V ≤ VOUT ≤ 5V, 9mm × 15mm × 2.3mm LGA Package LTM4605 5A to 12A Buck-Boost µModule Regulator 4.5V ≤ VIN ≤ 20V; 0.8V ≤ VOUT ≤ 16V, 15mm × 15mm × 2.8mm LGA Package LTM4607 5A to 12A Buck-Boost µModule Regulator 4.5V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 25V, 15mm × 15mm × 2.8mm LGA Package LTM8020 High VIN 0.2A DC/DC Step-Down µModule Regulator 4V ≤ VIN ≤ 36V; 1.25V ≤ VOUT ≤ 5V, 6.25mm × 6.25mm × 2.3mm LGA Package LTM8021 High VIN 0.5A DC/DC Step-Down µModule Regulator 3V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 5V, 6.25mm × 11.25mm × 2.8mm LGA Package LTM8022 High VIN 1A DC/DC Step-Down µModule Regulator 3.6V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 10V, 11.25mm × 9mm × 2.8mm LGA Package LTM8023 High VIN 2A DC/DC Step-Down µModule Regulator 3.6V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 10V, 11.25mm × 9mm × 2.8mm LGA Package 4608afc 26 Linear Technology Corporation LT 0311 REV C • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear.com LINEAR TECHNOLOGY CORPORATION 2008