LTM8073 60VIN, 3A Silent Switcher µModule Regulator Features Description Complete Step-Down Switch Mode Power Supply nn Low Noise Silent Switcher® Architecture nn Wide Input Voltage Range: 3.4V to 60V nn Wide Output Voltage Range: 0.8V to 15V nn 3A Continuous Output Current, 24V , 5V IN OUT, TA = 85°C nn Up to 5A Peak Current nn Parallelable for Increased Output Current nn Selectable Switching Frequency: 200kHz to 3MHz nn Programmable Soft-Start nn 6.25mm × 9mm × 3.32mm BGA Package The LTM®8073 is a 60VIN, 3A (continuous) or 5A (peak) step-down Silent Switcher µModule® (power module) regulator. Included in the package are the switching controller, power switches, inductor, and all support components. Operating over an input voltage range of 3.4V to 60V, the LTM8073 supports an output voltage range of 0.8V to 15V and a switching frequency range of 200kHz to 3MHz, each set by a single resistor. Only the input and output filter capacitors are needed to finish the design. nn The low profile package enables utilization of unused space on the bottom of PC boards for high density point of load regulation. The LTM8073 is packaged in a thermally enhanced, compact over-molded ball grid array (BGA) package suitable for automated assembly by standard surface mount equipment. The LTM8073 is RoHS compliant. Applications Power for Portable Products Distributed Supply Regulation nn Industrial Supplies nn Wall Transformer Regulation nn nn L, LT, LTC, LTM, µModule, Burst Mode, Silent Switcher, Linear Technology and the Linear logo are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. Typical Application 5VOUT from 7VIN to 60VIN Step-Down Converter 95 BIAS AUX RUN 1µF VOUT 5V 3A VOUT RT 32.4k 1.2MHz GND SYNC FB 47.5k 100µF 8073 TA01a PINS NOT USED IN THIS CIRCUIT: TR/SS, PG, SHARE EFFICIENCY (%) LTM8073 VIN VIN 7V TO 60V Efficiency, VOUT = 5V, BIAS = 5V BIAS = 5V VIN = 24V 90 85 80 0 1 2 LOAD CURRENT (A) 3 8073 TA01 8073fa For more information www.linear.com/LTM8073 1 LTM8073 Absolute Maximum Ratings Pin Configuration (Notes 1, 2) VIN, RUN Voltage.......................................................65V PG Voltage.................................................................42V AUX, VOUT, BIAS Voltage...........................................19V FB, TR/SS Voltage.......................................................4V SYNC Voltage...............................................................6V Maximum Internal Temperature (Note 4)............... 125°C Storage Temperature.............................. –55°C to 125°C Peak Solder Reflow (Package Body) Temperature...250°C TOP VIEW BANK 2 VIN RUN GND 6 5 4 AUX BIAS RT TR/SS SHARE SYNC 1 BANK 3 GND VOUT PG 3 2 BANK 1 GND FB A B C D E F G H 48-LEAD (9mm × 6.25mm × 3.32mm) BGA PACKAGE TJMAX = 125°C, θJA = 23.6°C/W, θJCbottom = 4.4°C/W, θJCtop = 11.3°C/W, θJB = 2.8°C/W, WEIGHT = 0.5g θ VALUES DETERMINED PER JEDEC 51-9, 51-12 Order Information http://www.linear.com/product/LTM8073#orderinfo PART MARKING* PART NUMBER LTM8073EY#PBF LTM8073IY#PBF TERMINAL FINISH DEVICE FINISH CODE PACKAGE TYPE MSL RATING TEMPERATURE RANGE (Note 3) SAC305 (RoHS) LTM8073 e1 BGA 3 –40°C to 125°C • Consult Marketing for parts specified with wider operating temperature ranges. *Device temperature grade is indicated by a label on the shipping container. Pad or ball finish code is per IPC/JEDEC J-STD-609. • Terminal Finish Part Marking: www.linear.com/leadfree • Recommended BGA PCB Assembly and Manufacturing Procedures: www.linear.com/umodule/pcbassembly • BGA Package and Tray Drawings: www.linear.com/packaging 8073fa 2 For more information www.linear.com/LTM8073 LTM8073 Electrical Characteristics The l denotes the specifications which apply over the specified operating temperature range, otherwise specifications are at TJ = 25°C. VIN = 12V, RUN = 2V, unless otherwise noted. PARAMETER CONDITIONS MIN Minimum Input Voltage VIN Rising Output DC Voltage RFB Open RFB = 14.3kΩ, VIN = 60V Peak Output DC Current VOUT = 3.3V, fSW = 1MHz Quiescent Current Into VIN RUN = 0V BIAS = 0V, No Load, SYNC = 0V, Not Switching 3 300 µA µA Quiescent Current Into BIAS BIAS = 5V, RUN = 0V BIAS = 5V, No Load, SYNC = 0V, Not Switching BIAS = 5V, VOUT = 3.3V, IOUT = 3A, fSW = 1MHz 1 275 12 µA µA mA Line Regulation 5.5V < VIN < 36V, IOUT = 1A 0.5 % Load Regulation 0.1A < IOUT < 3A 0.5 % Output Voltage Ripple IOUT = 3A 10 mV Switching Frequency RT = 232kΩ RT = 41.2kΩ RT = 10.7kΩ 200 0.95 3 kHz MHz MHz 3.4 772 802 0.9 RUN Current TR/SS = 0V TR/SS Pull-Down PG Threshold Voltage at FB (Upper) V A (Note 5) RUN Threshold Voltage UNITS V V 5 l TR/SS Current MAX 0.8 15 Voltage at FB Minimum BIAS Voltage TYP l 817 mV 3.2 V 1.06 V 1 µA 2 µA TR/SS = 0.1V 200 Ω FB Falling (Note 6) 0.88 V PG Threshold Voltage at FB (Lower) FB Rising (Note 6) 0.73 PG Leakage Current PG = 42V PG Sink Current PG = 0.1V V 1 150 µA µA SYNC Threshold Voltage Synchronization 0.4 1.5 V SYNC Voltage To Enable Spread Spectrum 2.9 4.2 V SYNC Current SYNC = 0V 35 µA 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: Unless otherwise noted, the absolute minimum voltage is zero. Note 3: The LTM8073E is guaranteed to meet performance specifications from 0°C to 125°C internal. Specifications over the full –40°C to 125°C internal operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTM8073I is guaranteed to meet specifications over the full –40°C to 125°C internal operating temperature range. Note that the maximum internal temperature is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. Note 4: The LTM8073 contains overtemperature protection that is intended to protect the device during momentary overload conditions. The internal temperature exceeds the maximum operating junction temperature when the overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 5. Below this specified voltage, internal circuitry will draw power from VIN. Note 6. PG transitions from low to high. 8073fa For more information www.linear.com/LTM8073 3 LTM8073 Typical Performance Characteristics Efficiency, VOUT = 0.8V, BIAS = 5V 12VIN 24VIN 36VIN 48VIN 60 80 70 12VIN 24VIN 36VIN 48VIN 60 0 1 2 3 LOAD CURRENT (A) 50 4 0 1 2 3 LOAD CURRENT (A) 8073 G01 95 50 12VIN 24VIN 36VIN 48VIN 0 1 2 3 LOAD CURRENT (A) 75 55 4 95 12VIN 24VIN 36VIN 48VIN 85 85 0 1 2 3 LOAD CURRENT (A) 0 1 2 3 LOAD CURRENT (A) 8073 G07 75 55 4 12VIN 24VIN 36VIN 48VIN 0 1 2 3 LOAD CURRENT (A) 95 Efficiency, VOUT = 5V, BIAS = 5V 85 75 55 4 8073 G06 Efficiency, VOUT = 3.3V, BIAS = 5V 12VIN 24VIN 36VIN 48VIN 65 4 4 Efficiency, VOUT = 2V, BIAS = 5V 65 EFFICIENCY (%) 95 EFFICIENCY (%) EFFICIENCY (%) Efficiency, VOUT = 2.5V, BIAS = 5V 12VIN 24VIN 36VIN 48VIN 2 3 LOAD CURRENT (A) 8073 G05 95 65 1 85 65 75 0 8073 G03 Efficiency, VOUT = 1.8V, BIAS = 5V 8073 G04 55 50 4 85 EFFICIENCY (%) EFFICIENCY (%) 80 60 12VIN 24VIN 36VIN 48VIN 8073 G02 Efficiency, VOUT = 1.5V, BIAS = 5V 70 70 60 EFFICIENCY (%) 90 Efficiency, VOUT = 1.2V, BIAS = 5V 90 80 70 50 Efficiency, VOUT = 1V, BIAS = 5V EFFICIENCY (%) EFFICIENCY (%) 80 90 EFFICIENCY (%) 90 TA = 25°C, unless otherwise noted. 0 1 2 3 LOAD CURRENT (A) 75 12VIN 24VIN 36VIN 48VIN 65 4 8073 G08 55 0 1 2 3 LOAD CURRENT (A) 4 8073 G09 8073fa 4 For more information www.linear.com/LTM8073 LTM8073 Typical Performance Characteristics Efficiency, VOUT = 8V, BIAS = 5V TA = 25°C, unless otherwise noted. Efficiency, VOUT = 12V, BIAS = 5V 90 90 90 80 12VIN 24VIN 36VIN 48VIN 70 60 0 1 2 3 LOAD CURRENT (A) EFFICIENCY (%) 100 EFFICIENCY (%) 100 80 24VIN 36VIN 48VIN 70 60 4 0 1 2 3 LOAD CURRENT (A) 80 80 80 12VIN 24VIN 36VIN 48VIN 0 1 2 3 LOAD CURRENT (A) EFFICIENCY (%) 90 EFFICIENCY (%) EFFICIENCY (%) 90 50 70 12VIN 24VIN 36VIN 48VIN 60 50 4 0 1 2 3 LOAD CURRENT (A) 90 50 EFFICIENCY (%) 1 2 LOAD CURRENT (A) 8073 G16 1 2 LOAD CURRENT (A) 3 0.75 70 12VIN 24VIN 36VIN 60 3 0 Input vs Load Current VOUT = 0.8V 80 0 12VIN 24VIN 36VIN 48VIN 8073 G15 90 80 50 70 Efficiency, VOUT = –15V, BIAS Tied to LTM8073 GND 12VIN 24VIN 36VIN 48VIN 4 8073 G14 Efficiency, VOUT = –12V, BIAS Tied to LTM8073 GND 60 2 3 LOAD CURRENT (A) 60 4 8073 G13 70 1 Efficiency, VOUT = –8V, BIAS Tied to LTM8073 GND 90 60 0 8073 G12 Efficiency, VOUT = –5V, BIAS Tied to LTM8073 GND 70 24VIN 36VIN 48VIN 8073 G11 Efficiency, VOUT = –3.3V, BIAS Tied to LTM8073 GND EFFICIENCY (%) 80 60 4 8073 G10 Efficiency, VOUT = 15V, BIAS 5V 70 INPUT CURRENT (A) EFFICIENCY (%) 100 50 0 1 LOAD CURRENT (A) 2 8073 G17 12VIN 24VIN 36VIN 48VIN 0.50 0.25 0 0 1 2 3 LOAD CURRENT (A) 4 5 8073 G18 8073fa For more information www.linear.com/LTM8073 5 LTM8073 Typical Performance Characteristics Input vs Load Current VOUT = 1.2V Input vs Load Current VOUT = 1V 1.00 1.00 0.25 0 1 2 3 LOAD CURRENT (A) 4 0.75 0.50 0.25 0 5 0 1 8073 G19 Input vs Load Current VOUT = 1.8V 1.5 12VIN 24VIN 36VIN 48VIN 1.0 0.5 0 0 1 2 3 LOAD CURRENT (A) 4 2 3 LOAD CURRENT (A) 4 0.5 0 0 1 2 3 LOAD CURRENT (A) 4 5 8073 G25 0 1 2 3 LOAD CURRENT (A) 4 0 1 2 3 LOAD CURRENT (A) 4 Input vs Load Current VOUT = 3.3V 12VIN 24VIN 36VIN 48VIN 1.5 1.0 0.5 0 5 0 1 3.0 3 1.0 0 1 2 3 LOAD CURRENT (A) 4 5 Input vs Load Current VOUT = 12V 24VIN 36VIN 48VIN 2.0 0 2 3 LOAD CURRENT (A) 8073 G24 Input vs Load Current VOUT = 8V 12VIN 24VIN 36VIN 48VIN 5 8073 G21 INPUT CURRENT (A) INPUT CURRENT (A) INPUT CURRENT (A) 1.0 0 2.0 0.5 4.0 1.5 0.25 8073 G23 Input vs Load Current VOUT = 5V 2.0 0.50 5 12VIN 24VIN 36VIN 48VIN 1.0 0 5 12VIN 24VIN 36VIN 48VIN 12VIN 24VIN 36VIN 48VIN 0.75 Input vs Load Current VOUT = 2.5V 8073 G22 2.5 Input vs Load Current VOUT = 1.5V 8073 G20 INPUT CURRENT (A) INPUT CURRENT (A) 1.5 INPUT CURRENT (A) 0.50 12VIN 24VIN 36VIN 48VIN INPUT CURRENT (A) 12VIN 24VIN 36VIN 48VIN INPUT CURRENT (A) INPUT CURRENT (A) 0.75 0 TA = 25°C, unless otherwise noted. 4 5 8073 G26 2 1 0 0 1 2 3 LOAD CURRENT (A) 4 5 8073 G27 8073fa 6 For more information www.linear.com/LTM8073 LTM8073 Typical Performance Characteristics 1.50 Input vs Load Current VOUT = –3.3V INPUT CURRENT (A) INPUT CURRENT (A) 2 1 0 0 1 2 3 LOAD CURRENT (A) 4 2.0 12VIN 24VIN 36VIN 48VIN 24VIN 36VIN 48VIN 1.00 INPUT CURRENT (A) 3 Input vs Load Current VOUT = 15V 0.50 0 5 0 1 2 3 LOAD CURRENT (A) 4 1.5 0.5 0 Input vs Load Current VOUT = –12V 1 2 LOAD CURRENT (A) 1.5 1.0 0 3 0 1 2 LOAD CURRENT (A) DROPOUT VOLTAGE (mV) BIAS CURRENT (mA) 8 0 1 2 SWITCHING FREQUENCY (MHz) 3 8073 G34 Input vs Load Current VOUT = –15V 12VIN 24VIN 36VIN 1.0 0 1 LOAD CURRENT (A) 2.0 1000 500 0 0 1 2 3 LOAD CURRENT (A) 4 5 8073 G35 2 8073 G33 Dropout Voltage vs Load Current VOUT = 5V, BIAS Open 4 0 4 1.5 0 3 INPUT CURRENT (A) 1500 12 2 3 LOAD CURRENT (A) 8073 G32 IBIAS vs Switching Frequency VBIAS = 5V, VIN = 24V 16 1 0.5 8073 G31 20 0 2.0 0.5 0 0.5 2.5 12VIN 24VIN 36VIN 48VIN 2.0 1.0 1.0 8073 G30 INPUT CURRENT (A) 2.5 INPUT CURRENT (A) INPUT CURRENT (A) Input vs Load Current VOUT = –8V 12VIN 24VIN 36VIN 48VIN 12VIN 24VIN 36VIN 48VIN 1.5 0 5 Input vs Load Current VOUT = –5V 8073 G29 8073 G28 2.0 TA = 25°C, unless otherwise noted. Input Current vs VIN VOUT Shorted, DC2389A Eval Board 1.5 1.0 0.5 0 0 10 20 30 INPUT VOLTAGE (V) 40 8073 G36 8073fa For more information www.linear.com/LTM8073 7 LTM8073 Typical Performance Characteristics Maximum Load Current vs VIN BIAS Tied to LTM8073 GND TA = 25°C, unless otherwise noted. Maximum Load Current vs VIN BIAS Tied to LTM8073 GND Derating, VOUT = 0.8V, BIAS = 5V, DC2389A Demo Board 5 3 5 4 3 2 –3.3VOUT –5VOUT –8VOUT 1 0 20 40 INPUT VOLTAGE (V) 2 1 –12VOUT –15VOUT 0 60 0 20 40 INPUT VOLTAGE (V) MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) 2 12VIN 24VIN 36VIN 48VIN 25 50 75 100 AMBIENT TEMPERATURE (°C) 3 2 12VIN 24VIN 36VIN 48VIN 1 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 12VIN 24VIN 36VIN 48VIN 1 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 4 3 2 12VIN 24VIN 36VIN 48VIN 125 Derating, VOUT = 3.3V, BIAS = 5V, DC2389A Demo Board 5 8073 G43 0 LFM 4 3 2 12VIN 24VIN 36VIN 48VIN 1 0 125 8073 G42 0 LFM MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) 2 0 125 5 0 LFM 25 50 75 100 AMBIENT TEMPERATURE (°C) 3 Derating, VOUT = 2.5V, BIAS = 5V, DC2389A Demo Board 5 0 4 8073 G41 Derating, VOUT = 1.8V, BIAS = 5V, DC2389A Demo Board 0 0 LFM 4 0 125 125 5 8073 G40 1 25 50 75 100 AMBIENT TEMPERATURE (oC) 0 LFM 3 0 0 Derating, VOUT = 1.5V, BIAS = 5V, DC2389A Demo Board 5 4 0 12VIN 24VIN 36VIN 48VIN 1 Derating, VOUT = 1.2V, BIAS = 5V, DC2389A Demo Board 0 LFM 1 2 8073 G39 MAXIMUM LOAD CURRENT (A) 5 3 8073 G38 8073 G37 Derating, VOUT = 1V, BIAS = 5V, DC2389A Demo Board 4 0 60 MAXIMUM LOAD CURRENT (A) 0 MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) 0 LFM 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 125 8073 G44 4 3 2 12VIN 24VIN 36VIN 48VIN 1 0 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 125 8073 G45 8073fa 8 For more information www.linear.com/LTM8073 LTM8073 Typical Performance Characteristics Derating, VOUT = 5V, BIAS = 5V, DC2389A Demo Board 5 5 Derating, VOUT = 8V, BIAS = 5V, DC2389A Demo Board 3 2 12VIN 24VIN 36VIN 48VIN 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 4 3 2 0 125 12VIN 24VIN 36VIN 48VIN 1 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 8073 G46 24VIN 36VIN 48VIN 2 1 12VIN 24VIN 36VIN 48VIN 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 2 1 0 125 12VIN 24VIN 36VIN 48VIN 0 8073 G50 25 50 75 100 AMBIENT TEMPERATURE (°C) 2.0 2.0 Derating, I-Grade VOUT = –15V, BIAS Tied to LTM8073 GND, DC2389A Demo Board 0 LFM MAXIMUM LOAD CURRENT (A) 2 1 12VIN 24VIN 36VIN 48VIN 125 8073 G52 MAXIMUM LOAD CURRENT (A) 0 LFM 0 LFM 1.5 1.0 0.5 0 12VIN 24VIN 36VIN 48VIN 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 125 8073 G51 Derating, I-Grade VOUT = –12V, BIAS Tied to LTM8073 GND, DC2389A Demo Board 3 MAXIMUM LOAD CURRENT (A) 0 LFM 3 0 125 125 3 Derating, I-Grade VOUT = –8V, BIAS Tied to LTM8073 GND, DC2389A Demo Board 25 50 75 100 AMBIENT TEMPERATURE (°C) 25 50 75 100 AMBIENT TEMPERATURE (°C) Derating, VOUT = –5V, BIAS Tied to LTM8073 GND, DC2389A Demo Board 8073 G49 0 0 8073 G48 MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) 2 0 24VIN 36VIN 48VIN 0 LFM 3 25 50 75 100 AMBIENT TEMPERATURE (°C) 1 0 125 4 0 LFM 0 2 Derating, VOUT = –3.3V, BIAS Tied to LTM8073 GND, DC2389A Demo Board 4 1 3 8073 G47 Derating, VOUT = 15V, BIAS = 5V, DC2389A Demo Board 0 0 LFM MAXIMUM LOAD CURRENT (A) 4 0 4 Derating, VOUT = 12V, BIAS = 5V, DC2389A Demo Board 0 LFM MAXIMUM LOAD CURRENT (A) MAXIMUM LOAD CURRENT (A) 0 LFM 1 TA = 25°C, unless otherwise noted. 125 8073 G53 1.5 1.0 0.5 0 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE (°C) 125 8073 G54 8073fa For more information www.linear.com/LTM8073 9 LTM8073 Typical Performance Characteristics 50 CISPR22 Class B Radiated DC2389A Demo Board, VOUT = 5V No Filter (FB1 Short, C8, C9 Open) 50 fSW = 1.2MHz, VIN = 28V, IOUT = 3.5A 40 AMPLITUDE (dBuV/m) AMPLITUDE (dBuV/m) CISPR22 Class B Radiated DC2389A Demo Board, VOUT = 5V No Filter (FB1 Short, C8, C9 Open) fSW = 1.2MHz, VIN = 14V, I OUT = 3.5A 40 30 20 10 CLASS B LIMIT HORIZONTAL VERTICAL 0 –10 TA = 25°C, unless otherwise noted. 0 200 400 600 FREQUENCY (MHz) 800 1000 30 20 10 CLASS B LIMIT HORIZONTAL VERTICAL 0 –10 0 8073 G55 200 400 600 FREQUENCY (MHz) 800 1000 8073 G56 Pin Functions GND (Bank 1, A1, A6, B3): Tie these GND pins to a local ground plane below the LTM8073 and the circuit components. In most applications, the bulk of the heat flow out of the LTM8073 is through these pads, so the printed circuit design has a large impact on the thermal performance of the part. See the PCB Layout and Thermal Considerations sections for more details. VIN (Bank 2): VIN supplies current to the LTM8073’s internal regulator and to the internal power switch. These pins must be locally bypassed with an external, low ESR capacitor; see Table 1 for recommended values. VOUT (Bank 3): Power Output Pins. Apply the output filter capacitor and the output load between these pins and GND pins. BIAS (Pin A2): The BIAS pin connects to the internal power bus. Connect to a power source greater than 3.2V. If VOUT is greater than 3.2V, connect this pin to AUX. Decouple this pin with at least 1µF if the voltage source for BIAS is remote. PG (Pin A3): The PG pin is the open-collector output of an internal comparator. PG remains low until the FB pin voltage is between 0.73V and 0.88V typical. The PG signal is valid when VIN is above 3.4V. If VIN is above 3.4V and RUN is low, PG will drive low. If this function is not used, leave this pin floating. SHARE (Pin A4): Tie this to the SHARE pin of another LTM8073 to load share. Otherwise leave floating. Do not drive this pin. RT (Pin A5): The RT pin is used to program the switching frequency of the LTM8073 by connecting a resistor from this pin to ground. The Applications Information section of the data sheet includes a table to determine the resistance value based on the desired switching frequency. Minimize capacitance at this pin. Do not drive this pin. FB (Pin B1): The LTM8073 regulates its FB pin to 0.8V. Connect the adjust resistor from this pin to ground. The value of RFB is given by the equation RFB = 199.7/(VOUT – 0.8), where RFB is in kΩ. 8073fa 10 For more information www.linear.com/LTM8073 LTM8073 Pin Functions AUX (Pin B2): Low Current Voltage Source for BIAS. In many designs, the BIAS pin is simply connected to VOUT. The AUX pin is internally connected to VOUT and is placed adjacent to the BIAS pin to ease printed circuit board routing. Also, some applications require a feed-forward capacitor; it can be connected from AUX to FB for convenient PCB routing. Although this pin is internally connected to VOUT, it is not intended to deliver a high current, so do not draw current from this pin to the load. pulse-skipping mode with spread spectrum modulation. 4) Synchronization mode. Drive this pin with a clock source to synchronize to an external frequency. During synchronization the part will operate in pulse-skipping mode. TR/SS (Pin B5): The TR/SS pin is used to provide a soft-start or tracking function. The internal 2μA pull-up current in combination with an external capacitor tied to this pin creates a voltage ramp. If TR/SS is less than 0.8V, the FB voltage tracks to this value. For tracking, tie a resistor divider to this pin from the tracked output. This pin is pulled to ground with an internal MOSFET during shutdown and fault conditions; use a series resistor if driving from a low impedance output. This pin may be left floating if the tracking function is not needed. SYNC (Pin B4): External clock synchronization input and operational mode. This pin programs four different operating modes: 1) Burst Mode®. Tie this pin to ground for Burst Mode operation at low output loads—this will result in low quiescent current. 2) Pulse-skipping mode. Float this pin for pulse-skipping mode. This mode offers full frequency operation down to low output loads before pulse-skipping mode occurs. 3) Spread spectrum mode. Tie this pin high (between 2.9V and 4.2V) for RUN (Pin B6): Pull the RUN pin below 0.9V to shut down the LTM8073. Tie to 1.06V or more for normal operation. If the shutdown feature is not used, tie this pin to the VIN pin. Block Diagram BIAS VIN AUX 0.2µF 2.2µH CURRENT MODE CONTROLLER VOUT 249k 10pF 0.1µF GND FB RUN SHARE TR/SS SYNC RT PG 8073 BD 8073fa For more information www.linear.com/LTM8073 11 LTM8073 Operation The LTM8073 is a standalone nonisolated step-down switching DC/DC power supply that can deliver up to 5A. The continuous current is determined by the internal operating temperature. It provides a precisely regulated output voltage programmable via one external resistor from 0.8V to 15V. The input voltage range is 3.4V to 60V. Given that the LTM8073 is a step-down converter, make sure that the input voltage is high enough to support the desired output voltage and load current. A simplified Block Diagram is given on the previous page. The LTM8073 contains a current mode controller, power switching elements, power inductor and a modest amount of input and output capacitance. The LTM8073 is a fixed frequency PWM regulator. The switching frequency is set by simply connecting the appropriate resistor value from the RT pin to GND. An internal regulator provides power to the control circuitry. This bias regulator normally draws power from the VIN pin, but if the BIAS pin is connected to an external voltage higher than 3.2V, bias power is drawn from the external source (typically the regulated output voltage). This improves efficiency. The RUN pin is used to place the LTM8073 in shutdown, disconnecting the output and reducing the input current to a few μA. To enhance efficiency, the LTM8073 automatically switches to Burst Mode operation in light or no load situations. Between bursts, all circuitry associated with controlling the output switch is shut down reducing the input supply current. The oscillator reduces the LTM8073’s operating frequency when the voltage at the FB pin is low. This frequency foldback helps to control the output current during start-up and overload. The TR/SS node acts as an auxiliary input to the error amplifier. The voltage at FB servos to the TR/SS voltage until TR/SS goes above about 0.8V. Soft-start is implemented by generating a voltage ramp at the TR/SS pin using an external capacitor which is charged by an internal constant current. Alternatively, driving the TR/SS pin with a signal source or resistive network provides a tracking function. Do not drive the TR/SS pin with a low impedance voltage source. See the Applications Information section for more details. The LTM8073 contains a power good comparator which trips when the FB pin is between 0.73V and 0.88V, typical. The PG output is an open-drain transistor that is off when the output is in regulation, allowing an external resistor to pull the PG pin high. The PG signal is valid when VIN is above 3.4V. If VIN is above 3.4V and RUN is low, PG will drive low. The LTM8073 is equipped with a thermal shutdown that inhibits power switching at high junction temperatures. The activation threshold of this function is above 125°C to avoid interfering with normal operation, so prolonged or repetitive operation under a condition in which the thermal shutdown activates may damage or impair the reliability of the device. 8073fa 12 For more information www.linear.com/LTM8073 LTM8073 Applications Information For most applications, the design process is straightforward, summarized as follows: 1. Look at Table 1 and find the row that has the desired input range and output voltage. 2. Apply the recommended CIN, COUT, RFB and RT values. 3. Apply the CFF (from AUX to FB) capacitor as required. 4. Connect BIAS as indicated. While these component combinations have been tested for proper operation, it is incumbent upon the user to verify proper operation over the intended system’s line, load and environmental conditions. Bear in mind that the maximum output current is limited by junction temperature, the relationship between the input and output voltage magnitude and polarity and other factors. Please refer to the graphs in the Typical Performance Characteristics section for guidance. The maximum frequency (and attendant RT value) at which the LTM8073 should be allowed to switch is given in Table 1 in the Maximum fSW column, while the recommended frequency (and RT value) for optimal efficiency over the given input condition is given in the fSW column. There are additional conditions that must be satisfied if the synchronization function is used. Please refer to the Synchronization section for details. Table 1. Recommended Component Values and Configuration (TA = 25°C) VIN (Note 1) VOUT RFB CIN (Note 2) COUT CFF BIAS fSW RT MAX fSW MIN RT 3.4V to 60V 0.8V Open 1µF 100V 1206 X7R 2× 100µF 4V 0805 X5R 47pF 5V 450kHz 95.3k 475kHz 90.9k 3.4V to 60V 1V 1M 1µF 100V 1206 X7R 2× 100µF 4V 0805 X5R 47pF 5V 450kHz 95.3k 550kHz 76.8k 3.4V to 60V 1.2V 499k 1µF 100V 1206 X7R 2× 100µF 4V 0805 X5R 47pF 5V 500kHz 84.5k 650kHz 63.4k 3.4V to 60V 1.5V 287k 1µF 100V 1206 X7R 100µF 4V 0805 X5R 27pF 5V 500kHz 84.5k 750kHz 54.9k 3.4V to 60V 1.8V 200k 1µF 100V 1206 X7R 100µF 4V 0805 X5R 10pF 5V 500kHz 84.5k 900kHz 45.6k 2V 169k 1µF 100V 1206 X7R 100µF 4V 0805 X5R 5V 600kHz 64.8k 950kHz 42.2k 4V to 60V 3.4V to 60V 2.5V 118k 1µF 100V 1206 X7R 100µF 4V 0805 X5R 5V 800kHz 51.1k 1.2MHz 32.4K 5V to 60V 3.3V 80.6k 1µF 100V 1206 X7R 100µF 4V 0805 X5R 5V 850kHz 47.5k 1.5MHz 24.3k 7V to 60V 5V 47.5k 1µF 100V 1206 X7R 100µF 6.3V 1206 X5R 5V 1.2MHz 32.4k 2.2MHz 16.9k 11V to 60V 8V 28k 1µF 100V 1206 X7R 47µF 16V 1210 X7R 5V 1.4MHz 26.7k 3MHZ 10k 16V to 60V 12V 17.8k 1µF 100V 1206 X7R 22µF 25V 1210 X5R 5V 1.4MHz 26.7k 3MHZ 10k 19.5V to 60V 15V 14.3k 1µF 100V 1206 X7R 22µF 25V 1210 X5R 5V 1.4MHz 26.7k 3MHZ 10k 3.4V to 56V –3.3V 80.6k 1µF 100V 1206 X7R 100µF 4V 0805 X5R LTM8073 GND 850kHz 47.5k 1.5MHz 24.3k 3.4V to 55V –5V 47.5k 1µF 100V 1206 X7R 100µF 6.3V 1206 X5R LTM8073 GND 1.2MHz 32.4k 2.2MHz 16.9k 3.4V to 52V –8V 28k 1µF 100V 1206 X7R 47µF 16V 1210 X7R LTM8073 GND 1.4MHz 26.7k 3MHZ 10k 3.4V to 48V –12V 17.8k 1µF 100V 1206 X7R 22µF 25V 1210 X5R LTM8073 GND 1.4MHz 26.7k 3MHZ 10k 3.4V to 45V –15V 14.3k 1µF 100V 1206 X7R 22µF 25V 1210 X5R LTM8073 GND 1.4MHz 26.7k 3MHZ 10k Note 1: The LTM8073 may be capable of lower input voltages but may skip switching cycles. Note 2: An input bulk capacitor is required. 8073fa For more information www.linear.com/LTM8073 13 LTM8073 Applications Information Capacitor Selection Considerations Frequency Selection The CIN and COUT capacitor values in Table 1 are the minimum recommended values for the associated operating conditions. Applying capacitor values below those indicated in Table 1 is not recommended, and may result in undesirable operation. Using larger values is generally acceptable, and can yield improved dynamic response, if it is necessary. Again, it is incumbent upon the user to verify proper operation over the intended system’s line, load and environmental conditions. The LTM8073 uses a constant frequency PWM architecture that can be programmed to switch from 200kHz to 3MHz by using a resistor tied from the RT pin to ground. Table 2 provides a list of RT resistor values and their resultant frequencies. Ceramic capacitors are small, robust and have very low ESR. However, not all ceramic capacitors are suitable. X5R and X7R types are stable over temperature and applied voltage and give dependable service. Other types, including Y5V and Z5U have very large temperature and voltage coefficients of capacitance. In an application circuit they may have only a small fraction of their nominal capacitance resulting in much higher output voltage ripple than expected. Ceramic capacitors are also piezoelectric. In Burst Mode operation, the LTM8073’s switching frequency depends on the load current, and can excite a ceramic capacitor at audio frequencies, generating audible noise. Since the LTM8073 operates at a lower current limit during Burst Mode operation, the noise is typically very quiet to a casual ear. If this audible noise is unacceptable, use a high performance electrolytic capacitor at the output. It may also be a parallel combination of a ceramic capacitor and a low cost electrolytic capacitor. A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LTM8073. A ceramic input capacitor combined with trace or cable inductance forms a high-Q (underdamped) tank circuit. If the LTM8073 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the device’s rating. This situation is easily avoided; see the Hot-Plugging Safely section. Table 2. SW Frequency vs RT Value fSW (MHz) RT (kΩ) 0.2 232 0.3 150 0.4 110 0.5 84.5 0.6 64.8 0.7 60.4 0.8 51.1 1.0 40.2 1.2 32.4 1.4 28.0 1.6 23.7 1.8 20.5 2.0 16.9 2.2 15.8 3.0 10 Operating Frequency Trade-Offs It is recommended that the user apply the optimal RT value given in Table 1 for the input and output operating condition. System level or other considerations, however, may necessitate another operating frequency. While the LTM8073 is flexible enough to accommodate a wide range of operating frequencies, a haphazardly chosen one may result in undesirable operation under certain operating or fault conditions. A frequency that is too high can reduce efficiency, generate excessive heat or even damage the LTM8073 if the output is overloaded or short-circuited. A frequency that is too low can result in a final design that has too much output ripple or too large of an output capacitor. 8073fa 14 For more information www.linear.com/LTM8073 LTM8073 Applications Information BIAS Pin Considerations The BIAS pin is used to provide drive power for the internal power switching stage and operate other internal circuitry. For proper operation, it must be powered by at least 3.2V. If the output voltage is programmed to 3.2V or higher, BIAS may be simply tied to AUX. If VOUT is less than 3.2V, BIAS can be tied to VIN or some other voltage source. If the BIAS pin voltage is too high, the efficiency of the LTM8073 may suffer. The optimum BIAS voltage is dependent upon many factors, such as load current, input voltage, output voltage and switching frequency. In all cases, ensure that the maximum voltage at the BIAS pin is less than 19V. If BIAS power is applied from a remote or noisy voltage source, it may be necessary to apply a decoupling capacitor locally to the pin. A 1µF ceramic capacitor works well. The BIAS pin may also be left open at the cost of a small degradation in efficiency. If the LTM8073 is configured to provide a negative output, do not connect BIAS to VOUT or AUX. Instead, tie to BIAS to the LTM8073 GND, which should be the negative output. Maximum Load The maximum practical continuous load that the LTM8073 can drive, while rated at 3A, actually depends upon both the internal current limit and the internal temperature. The internal current limit is designed to prevent damage to the LTM8073 in the case of overload or short-circuit. The internal temperature of the LTM8073 depends upon operating conditions such as the ambient temperature, the power delivered, and the heat sinking capability of the system. For example, if the LTM8073 is configured to regulate at 1.2V, it may continuously deliver 4.5A from 12VIN if the ambient temperature is controlled to less than 55°C; this is more than the 3A continuous rating. Please see the derating curve for VOUT = 1.2V in the Typical Performance Characteristics section. Similarly, if the output voltage is 15V and the ambient temperature is 95°C, the LTM8073 will deliver at most 2A from 24VIN, which is less than the 3A continuous rating. paralleled LTM8073s together. To ensure that paralleled modules start up together, the TR/SS pins may be tied together, as well. If it is inconvenient to tie the TR/SS pins together, make sure that the same valued soft-start capacitors are used for each µModule regulator. An example of two LTM8073s configured for load sharing is given in the Typical Applications section. For closer load sharing, synchronize the LTM8073s to an external clock source. When load sharing among n units and using a single RFB resistor, the value of the resistor is: RFB = 199.7 n ( VOUT – 0.8 ) where RFB is in kΩ. Burst Mode Operation To enhance efficiency at light loads, the LTM8073 automatically switches to Burst Mode operation which keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current. During Burst Mode operation, the LTM8073 delivers single cycle bursts of current to the output capacitor followed by sleep periods where most of the internal circuitry is powered off and energy is delivered to the load by the output capacitor. During the sleep time, VIN and BIAS quiescent currents are greatly reduced, so, as the load current decreases towards a no load condition, the percentage of time that the LTM8073 operates in sleep mode increases and the average input current is greatly reduced, resulting in higher light load efficiency. Burst Mode operation is enabled by tying SYNC to GND. Minimum Input Voltage The LTM8073 is a step-down converter, so a minimum amount of headroom is required to keep the output in regulation. Keep the input above 3.4V to ensure proper operation. Voltage transients or ripple valleys that cause the input to fall below 3.4V may turn off the LTM8073. Load Sharing Output Voltage Tracking and Soft-Start LTM8073s may be paralleled to produce higher currents. To do this, tie the VIN, VOUT and SHARE pins of all the The LTM8073 allows the user to program its output voltage ramp rate by means of the TR/SS pin. An internal 2μA 8073fa For more information www.linear.com/LTM8073 15 LTM8073 Applications Information pulls up the TR/SS pin to about 2.4V. Putting an external capacitor on TR/SS enables soft starting the output to reduce current surges on the input supply. During the softstart ramp the output voltage will proportionally track the TR/SS pin voltage. For output tracking applications, TR/SS can be externally driven by another voltage source. From 0V to 0.8V, the TR/SS voltage will override the internal 0.8V reference input to the error amplifier, thus regulating the FB pin voltage to that of the TR/SS pin. When TR/SS is above 0.8V, tracking is disabled and the feedback voltage will regulate to the internal reference voltage. The TR/SS pin may be left floating if the function is not needed. pin, the SYNC pin is floated or held high, the frequency foldback is disabled and the switching frequency will slow down only during overcurrent conditions. An active pull-down circuit is connected to the TR/SS pin which will discharge the external soft-start capacitor in the case of fault conditions and restart the ramp when the faults are cleared. Fault conditions that clear the soft-start capacitor are the RUN pin transitioning low, VIN voltage falling too low, or thermal shutdown. The LTM8073 will not enter Burst Mode operation at low output loads while synchronized to an external clock, but instead will pulse skip to maintain regulation. The LTM8073 may be synchronized over a 200kHz to 3MHz range. The RT resistor should be chosen to set the LTM8073 switching frequency equal to or below the lowest synchronization input. For example, if the synchronization signal will be 500kHz and higher, the RT should be selected for 500kHz. Prebiased Output As discussed in the Output Voltage Tracking and Soft-Start section, the LTM8073 regulates the output to the FB voltage determined by the TR/SS pin whenever TR/SS is less than 0.8V. If the LTM8073 output is higher than the target output voltage, the LTM8073 will attempt to regulate the output to the target voltage by returning a small amount of energy back to the input supply. If there is nothing loading the input supply, its voltage may rise. Take care that it does not rise so high that the input voltage exceeds the absolute maximum rating of the LTM8073. Frequency Foldback The LTM8073 is equipped with frequency foldback which acts to reduce the thermal and energy stress on the internal power elements during a short-circuit or output overload condition. If the LTM8073 detects that the output has fallen out of regulation, the switching frequency is reduced as a function of how far the output is below the target voltage. This in turn limits the amount of energy that can be delivered to the load under fault. During the start-up time, frequency foldback is also active to limit the energy delivered to the potentially large output capacitance of the load. When a clock is applied to the SYNC Synchronization To select low ripple Burst Mode operation, tie the SYNC pin below about 0.4V (this can be ground or a logic low output). To synchronize the LTM8073 oscillator to an external frequency connect a square wave (with about 20% to 80% duty cycle) to the SYNC pin. The square wave amplitude should have valleys that are below 0.4V and peaks above 1.5V. For some applications it is desirable for the LTM8073 to operate in pulse-skipping mode, offering two major differences from Burst Mode operation. The first is that the clock stays awake at all times and all switching cycles are aligned to the clock. Second is that full switching frequency is reached at lower output load than in Burst Mode operation. These two differences come at the expense of increased quiescent current. To enable pulse-skipping mode, the SYNC pin is floated. The LTM8073 features spread spectrum operation to further reduce EMI/EMC emissions. To enable spread spectrum operation, apply between 2.9V and 4.2V to the SYNC pin. In this mode, triangular frequency modulation is used to vary the switching frequency between the value programmed by RT to about 20% higher than that value. The modulation frequency is about 3kHz. For example, when the LTM8073 is programmed to 2MHz, the frequency will vary from 2MHz to 2.4MHz at a 3kHz rate. When spread spectrum operation is selected, Burst Mode operation is disabled, and the part will run in pulse-skipping mode. The LTM8073 does not operate in forced continuous mode regardless of SYNC signal. 8073fa 16 For more information www.linear.com/LTM8073 LTM8073 Applications Information Negative Output VIN The LTM8073 is capable of generating a negative output voltage by connected its VOUT to system GND and the LTM8073 GND to the negative voltage rail. An example of this is shown in the Typical Applications section. The most versatile way to generate a negative output is to use a dedicated regulator that was designed to generate a negative voltage, but using a buck regulator like the LTM8073 to generate a negative voltage is a simple and cost effective solution, as long as certain restrictions are kept in mind. Figure 1a shows a typical negative output voltage application. Note that LTM8073 VOUT is tied to system GND and input power is applied from VIN to LTM8073 VOUT. As a result, the LTM8073 is not behaving as a true buck regulator, and the maximum output current is depends upon the input voltage. In the example shown in the Typical Applications section, there is an attending graph that shows how much current the LTM8073 deliver for given input voltages. VIN VIN VIN VOUT LTM8073 GND FAST LOAD TRANSIENT OUTPUT TRANSIENT RESPONSE 8073 F01b Figure 1b. Any Output Voltage Transient Appears on LTM8073 GND The CIN and COUT capacitors in figure 1c form an AC divider at the negative output voltage node. If VIN is hotplugged or rises quickly, the resultant VOUT will be a positive transient, which may be unhealthy for the application load. An antiparallel Schottky diode may be able to prevent this positive transient from damaging the load. The location of this Schottky diode is important. For example, in a system where the LTM8073 is far away from the load, placing the Schottky diode closest to the most sensitive load component may be the best design choice. Carefully evaluate whether the negative buck configuration is suitable for the application. VOUT FAST VIN TRANSIENT LTM8073 OUTPUT EXPERIENCES A POSITIVE TRANSIENT VIN GND VIN NEGATIVE OUTPUT VOLTAGE 8073 F01a CIN Figure 1a. The LTM8073 Can Be Used to Generate a Negative Voltage Note that this configuration requires that any load current transient will directly impress the transient voltage onto the LTM8073 GND, as shown in Figure 1b, so fast load transients can disrupt the LTM8073’s operation or even cause damage. Carefully evaluate whether the negative buck configuration is suitable for the application. VOUT LTM8073 COUT GND AC DIVIDER OPTIONAL SCHOTTKY DIODE 8073 F01c Figure 1c. A Schottky Diode Can Limit the Transient Caused by a Fast Rising VIN to Safe Levels If the LTM8073 is configured to provide a negative output, do not connect BIAS to VOUT or AUX. Instead, tie to BIAS to the LTM8073 GND, which should be the negative output. 8073fa For more information www.linear.com/LTM8073 17 LTM8073 Applications Information Shorted Input Protection Care needs to be taken in systems where the output is held high when the input to the LTM8073 is absent. This may occur in battery charging applications or in battery backup systems where a battery or some other supply is diode OR-ed with the LTM8073’s output. If the VIN pin is allowed to float and the RUN pin is held high (either by a logic signal or because it is tied to VIN), then the LTM8073’s internal circuitry pulls its quiescent current through its internal power switch. This is fine if your system can tolerate a few milliamps in this state. If you ground the RUN pin, the internal current drops to essentially zero. However, if the VIN pin is grounded while the output is held high, parasitic diodes inside the LTM8073 can pull large currents from the output through the VIN pin. Figure 2 shows a circuit that runs only when the input voltage is present and that protects against a shorted or reversed input. VIN VIN LTM8073 RUN 8073 F02 Figure 2. The Input Diode Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output. It Also Protects the Circuit from a Reversed Input. The LTM8073 Runs Only When the Input Is Present. PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8073. The LTM8073 is nevertheless a switching power supply, and care must be taken to minimize EMI and ensure proper operation. Even with the high level of integration, you may fail to achieve specified operation with a haphazard or poor layout. See Figure 3 for a suggested layout. Ensure that the grounding and heat sinking are acceptable. A few rules to keep in mind are: 1. Place CFF, RFB and RT as close as possible to their respective pins. 2. Place the CIN capacitor as close as possible to the VIN and GND connection of the LTM8073. 3. Place the COUT capacitor as close as possible to the VOUT and GND connection of the LTM8073. 4. Place the CIN and COUT capacitors such that their ground current flow directly adjacent to or underneath the LTM8073. 5. Connect all of the GND connections to as large a copper pour or plane area as possible on the top layer. Avoid breaking the ground connection between the external components and the LTM8073. 6. Use vias to connect the GND copper area to the board’s internal ground planes. Liberally distribute these GND vias to provide both a good ground connection and thermal path to the internal planes of the printed circuit board. Pay attention to the location and density of the thermal vias in Figure 3. The LTM8073 can benefit from the heat-sinking afforded by vias that connect to internal GND planes at these locations, due to their proximity to internal power handling components. The optimum number of thermal vias depends upon the printed circuit board design. For example, a board might use very small via holes. It should employ more thermal vias than a board that uses larger holes. 8073fa 18 For more information www.linear.com/LTM8073 LTM8073 Applications Information overshoot. The extra capacitor improves low frequency ripple filtering and can slightly improve the efficiency of the circuit, though it is likely to be the largest component in the circuit. VIN CIN GND GND RUN RT Thermal Considerations RT TR/SS SHARE SYNC PC BIAS AUX FB RFB GND COUT VOUT GND/THERMAL VIAS 8073 F03 Figure 3. Layout Showing Suggested External Components, GND Plane and Thermal Vias Hot-Plugging Safely The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of LTM8073. However, these capacitors can cause problems if the LTM8073 is plugged into a live supply (see Linear Technology Application Note 88 for a complete discussion). The low loss ceramic capacitor combined with stray inductance in series with the power source forms an underdamped tank circuit, and the voltage at the VIN pin of the LTM8073 can ring to more than twice the nominal input voltage, possibly exceeding the LTM8073’s rating and damaging the part. If the input supply is poorly controlled or the LTM8073 is hot-plugged into an energized supply, the input network should be designed to prevent this overshoot. This can be accomplished by installing a small resistor in series to VIN, but the most popular method of controlling input voltage overshoot is add an electrolytic bulk cap to the VIN net. This capacitor’s relatively high equivalent series resistance damps the circuit and eliminates the voltage The LTM8073 output current may need to be derated if it is required to operate in a high ambient temperature. The amount of current derating is dependent upon the input voltage, output power and ambient temperature. The derating curves given in the Typical Performance Characteristics section can be used as a guide. These curves were generated by the LTM8073 mounted to a 58cm2 4-layer FR4 printed circuit board. Boards of other sizes and layer count can exhibit different thermal behavior, so it is incumbent upon the user to verify proper operation over the intended system’s line, load and environmental operating conditions. For increased accuracy and fidelity to the actual application, many designers use FEA (finite element analysis) to predict thermal performance. To that end, Page 2 of the data sheet typically gives four thermal coefficients: θJA – Thermal resistance from junction to ambient θJCbottom – Thermal resistance from junction to the bottom of the product case θJCtop – Thermal resistance from junction to top of the product case θJB – Thermal resistance from junction to the printed circuit board. While the meaning of each of these coefficients may seem to be intuitive, JEDEC has defined each to avoid confusion and inconsistency. These definitions are given in JESD 51-12, and are quoted or paraphrased below: θJA is the natural convection junction-to-ambient air thermal resistance measured in a one cubic foot sealed enclosure. This environment is sometimes referred to as still 8073fa For more information www.linear.com/LTM8073 19 LTM8073 Applications Information air although natural convection causes the air to move. This value is determined with the part mounted to a JESD 51-9 defined test board, which does not reflect an actual application or viable operating condition. θJCbottom is the junction-to-board thermal resistance with all of the component power dissipation flowing through the bottom of the package. In the typical µModule regulator, the bulk of the heat flows out the bottom of the package, but there is always heat flow out into the ambient environment. As a result, this thermal resistance value may be useful for comparing packages but the test conditions don’t generally match the user’s application. θJCtop is determined with nearly all of the component power dissipation flowing through the top of the package. As the electrical connections of the typical µModule regulator are on the bottom of the package, it is rare for an application to operate such that most of the heat flows from the junction to the top of the part. As in the case of θJCbottom, this value may be useful for comparing packages but the test conditions don’t generally match the user’s application. θJB is the junction-to-board thermal resistance where almost all of the heat flows through the bottom of the µModule regulator and into the board, and is often just the sum of the θJCbottom and the thermal resistance of the bottom of the part through the solder joints and through a portion of the board. The board temperature is measured a specified distance from the package, using a two sided, two layer board. This board is described in JESD 51-9. Given these definitions, it should now be apparent that none of these thermal coefficients reflects an actual physical operating condition of a µModule regulator. Thus, none of them can be individually used to accurately predict the thermal performance of the product. Likewise, it would be inappropriate to attempt to use any one coefficient to correlate to the junction temperature vs load graphs given in the product’s data sheet. The only appropriate way to use the coefficients is when running a detailed thermal analysis, such as FEA, which considers all of the thermal resistances simultaneously. A graphical representation of these thermal resistances is given in Figure 4. The blue resistances are contained within the µModule regulator, and the green are outside. The die temperature of the LTM8073 must be lower than the maximum rating of 125°C, so care should be taken in the layout of the circuit to ensure good heat sinking of the LTM8073. The bulk of the heat flow out of the LTM8073 is through the bottom of the package and the pads into the printed circuit board. Consequently a poor printed circuit board design can cause excessive heating, resulting in impaired performance or reliability. Please refer to the PCB Layout section for printed circuit board design suggestions. JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD) JUNCTION-TO-CASE (TOP) RESISTANCE JUNCTION CASE (TOP)-TO-AMBIENT RESISTANCE JUNCTION-TO-BOARD RESISTANCE JUNCTION-TO-CASE CASE (BOTTOM)-TO-BOARD (BOTTOM) RESISTANCE RESISTANCE AMBIENT BOARD-TO-AMBIENT RESISTANCE 8073 F04 µMODULE REGULATOR Figure 4: Graphical Representation of the Thermal Resistances Between the Device Junction and Ambient 8073fa 20 For more information www.linear.com/LTM8073 LTM8073 Typical Applications 15VOUT from 19.5VIN to 60VIN Step-Down Converter. BIAS Is Tied to AUX LTM8073 VIN VIN 19.5V TO 60V BIAS AUX RUN 1µF VOUT 15V 2.7A VOUT RT 26.7k 1.4MHz FB GND 22µF SYNC 14.3k 8073 TA02 PINS NOT USED IN THIS CIRCUIT: TR/SS, PG, SHARE 1.2VOUT from 3.4VIN to 60VIN Step-Down Converter. BIAS Is Tied to an External 3.3V Source LTM8073 VIN VIN 3.4V TO 60V RUN 1µF EXT 3.3V VOUT AUX BIAS RT 47pf GND SYNC FB 100µF ×2 VOUT 1.2V 3.5A 499k 84.5k 500kHz PINS NOT USED IN THIS CIRCUIT: TR/SS, PG, SHARE 8073 TA03 2.5VOUT from 4VIN to 15VIN Step-Down Converter. BIAS Is Tied to VIN LTM8073 VIN VIN 4V TO 15V RUN BIAS VOUT 1µF 100µF RT 51.1k 800kHz GND SYNC FB VOUT 2.5V 3.3A 118k PINS NOT USED IN THIS CIRCUIT: TR/SS, PG, SHARE, AUX 8073 TA04 8073fa For more information www.linear.com/LTM8073 21 LTM8073 Typical Applications –5VOUT from 3.4VIN to 55VIN Positive to Negative Converter. BIAS Tied to LTM8073 GND Maximum Load Current vs VIN, BIAS Tied to LTM8073 GND INPUT BULK CAP 5 VIN LTM8073 RUN OPTIONAL SCHOTTKY DIODE VOUT 1µF 32.4k 1.2MHz RT FB GND SYNC BIAS 100µF 47.5k VOUT –5V PINS NOT USED IN THIS CIRCUIT: TR/SS, PG, SHARE, AUX MAXIMUM LOAD CURRENT (A) + VIN 3.4V TO 35V 4 3 2 1 0 8073 TA05a 0 20 40 INPUT VOLTAGE (V) 60 8073 TA05b Use Two LTM8073s Powered from the Same Input Source to Get More Output Current VIN VIN 7V TO 40V LTM8073 BIAS AUX RUN 1µF VOUT 3.3V 6.5A CONTINUOUS 10A PEAK VOUT RT 47.5k 850kHz FB TR/SS GND SYNC SHARE 100µF OPTIONAL SYNC TR/SS VIN LTM8073 SHARE BIAS AUX RUN 1µF VOUT RT 47.5k 850kHz 100µF FB GND SYNC 40.2k OPTIONAL SYNC PIN NOT USED IN THIS CIRCUIT: PG 8073 TA06 8073fa 22 For more information www.linear.com/LTM8073 LTM8073 Package Description Table 3. LTM8073 Pinout (Sorted by Pin Number) PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME A1 GND B1 FB C1 GND D1 GND E1 GND F1 GND G1 VOUT H1 VOUT A2 BIAS B2 AUX C2 GND D2 GND E2 GND F2 GND G2 VOUT H2 VOUT A3 PG B3 GND C3 VIN D3 GND E3 GND F3 GND G3 VOUT H3 VOUT A4 SHARE B4 SYNC C4 VIN D4 GND E4 GND F4 GND G4 VOUT H4 VOUT A5 RT B5 TR/SS C5 VIN D5 GND E5 GND F5 GND G5 VOUT H5 VOUT A6 GND B6 RUN C6 VIN D6 GND E6 GND F6 GND G6 VOUT H6 VOUT Package Photos 8073fa For more information www.linear.com/LTM8073 23 aaa Z 0.50 ±0.025 Ø 48x 2.5 2.5 SUGGESTED PCB LAYOUT TOP VIEW 1.5 PACKAGE TOP VIEW E 0.000 4 0.5 PIN “A1” CORNER 0.5 24 1.5 Y For more information www.linear.com/LTM8073 3.5 2.5 1.5 0.5 0.000 0.5 1.5 2.5 3.5 X D SYMBOL A A1 A2 b b1 D E e F G H1 H2 aaa bbb ccc ddd eee aaa Z NOM 3.32 0.50 2.82 0.60 0.50 9.00 6.25 1.00 7.00 5.00 0.32 2.50 DIMENSIONS 0.37 2.55 0.15 0.10 0.20 0.25 0.10 MAX 3.52 0.60 2.92 0.70 0.53 TOTAL NUMBER OF BALLS: 48 0.27 2.45 H1 SUBSTRATE A1 ddd M Z X Y eee M Z DETAIL A Øb (48 PLACES) // bbb Z MIN 3.12 0.40 2.72 0.50 0.47 b1 DETAIL B H2 MOLD CAP ccc Z MOLD CAP HT SUBSTRATE THK BALL DIMENSION PAD DIMENSION BALL HT NOTES DETAIL B PACKAGE SIDE VIEW A2 A Z F e b 6 4 G 3 e 2 PACKAGE BOTTOM VIEW b 5 1 DETAIL A PIN 1 3 SEE NOTES H G F E D C B A 7 SEE NOTES 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 BALL DESIGNATION PER JEP95 7 TRAY PIN 1 BEVEL ! PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX µModule BGA 48 0217 REV A PACKAGE ROW AND COLUMN LABELING MAY VARY AMONG µModule PRODUCTS. REVIEW EACH PACKAGE LAYOUT CAREFULLY 6. SOLDER BALL COMPOSITION IS 96.5% Sn/3.0% Ag/0.5% Cu 5. PRIMARY DATUM -Z- IS SEATING PLANE 4 3 2. ALL DIMENSIONS ARE IN MILLIMETERS NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 COMPONENT PIN “A1” (Reference LTC DWG # 05-08-1999 Rev A) BGA Package 48-Lead (9mm × 6.25mm × 3.32mm) LTM8073 Package Description Please refer to http://www.linear.com/product/LTM8073#packaging for the most recent package drawings. 8073fa LTM8073 Revision History REV DATE DESCRIPTION PAGE NUMBER A 08/17 Changed recomended BIAS pin connection from Open to LTM8073 GND for the negative voltage output application. 5, 8, 9, 13, 22 Updated derating curves. Changed minimum storage temperature from –50°C to –55°C. 8, 9 2 8073fa 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 representaFor more www.linear.com/LTM8073 tion that the interconnection of itsinformation circuits as described herein will not infringe on existing patent rights. 25 LTM8073 Typical Application 1VOUT from 3.4VIN to 60VIN Step-Down Converter with Spread Spectrum. BIAS Is Tied to an External 3.3V Source LTM8073 VIN VIN 3.4V TO 60V RUN 1µF EXT 3.3V VOUT BIAS SYNC AUX 47pF GND PINS NOT USED IN THIS CIRCUIT: TR/SS, PG, SHARE FB RT 100µF ×2 VOUT 1V 3.4A 8073 TA07 95.3k 450kHz Design Resources SUBJECT DESCRIPTION µModule Design and Manufacturing Resources Design: • Selector Guides • Demo Boards and Gerber Files • Free Simulation Tools µModule Regulator Products Search 1. Sort table of products by parameters and download the result as a spread sheet. Manufacturing: • Quick Start Guide • PCB Design, Assembly and Manufacturing Guidelines • Package and Board Level Reliability 2. Search using the Quick Power Search parametric table. TechClip Videos Quick videos detailing how to bench test electrical and thermal performance of µModule products. Digital Power System Management Linear Technology’s family of digital power supply management ICs are highly integrated solutions that offer essential functions, including power supply monitoring, supervision, margining and sequencing, and feature EEPROM for storing user configurations and fault logging. Related Parts PART NUMBER DESCRIPTION COMMENTS LTM8050 58V, 2A Step-Down µModule Regulator 3.6V ≤ VIN ≤ 58V, 0.8V ≤ VOUT ≤ 24V, 9mm × 15mm × 4.92mm BGA LTM8027 60V, 4A Step-Down µModule Regulator 4.5V ≤ VIN ≤ 60V, 2.5V ≤ VOUT ≤ 24V, 15mm × 15mm × 4.92mm BGA LTM8064 58V, 6A CVCC Step-Down µModule Regulator 6V ≤ VIN ≤ 58V, 1.2V ≤ VOUT ≤ 36V, 11.9mm × 16mm × 4.92mm BGA LTM8056 58VIN, 48VOUT Buck-Boost µModule Regulator 5V ≤ VIN ≤ 58V, 1.2V ≤ VOUT ≤ 48V, 15mm × 15mm × 4.92mm BGA LTM8053 40V, 3.5A/6A Step Down Silent Switcher µModule Regulator 3.4V ≤ VIN ≤ 40V, 0.97V ≤ VOUT ≤ 15V, 6.25mm × 9mm × 3.32mm BGA LTM8003 LTM8053 with H-Grade (150°C Operation) and FMAE Compliant 3.4V ≤ VIN ≤ 40V. 0.97V ≤ VOUT ≤ 18V, 6.25mm × 9mm × 3.32mm BGA Pinout LTM8032 36V, 2A Low EMI Step-Down µModule Regulator 3.6V ≤ VIN ≤ 36V, 0.8V ≤ VOUT ≤ 10V, EN55022B Compliant LTM8033 36V, 3A Low EMI Step-Down µModule Regulator 3.6V ≤ VIN ≤ 36V. 0.8V ≤ VOUT ≤ 24V, EN55022B Compliant 8073fa 26 LT 0817 REV A • PRINTED IN USA For more information www.linear.com/LTM8073 www.linear.com/LTM8073 LINEAR TECHNOLOGY CORPORATION 2017