LTM8027 60V, 4A DC/DC µModule Regulator Features Description Complete Switch Mode Power Supply n Wide Input Voltage Range: 4.5V to 60V (7.5V Minimum Voltage to Start) n Wide Output Voltage Range: 2.5V to 24V (See Table 2) n 4A Output Current n Programmable Soft-Start n 9µA Shutdown Supply Current n Selectable Switching Frequency Current Mode Control n Up to 95% Efficiency n Pb-Free (e4) RoHS Compliant Package with Gold Pad Finish n Tiny, Low Profile (15mm × 15mm × 4.32mm) Surface Mount LGA Package The LTM®8027 is a complete 4A, DC/DC step-down power supply. Included in the package are the switching controller, power switches, inductor and all support components. Operating over an input voltage range of 4.5V to 60V (7.5V minimum voltage to start), the LTM8027 supports output voltages up to 24V, and a switching frequency range of 100kHz to 500kHz, each set by a single resistor. Only the bulk input and output filter capacitors are needed to finish the design. n The low profile package (4.32mm) enables utilization of unused space on the bottom of PC boards for high density point of load regulation. A built-in soft-start timer is adjustable with a small capacitor. The LTM8027 is packaged in a thermally enhanced, compact (15mm × 15mm) and low profile (4.32mm) over-molded land grid array (LGA) package suitable for automated assembly by standard surface mount equipment. The LTM8027 is Pb-free and RoHS compliant. Applications n n n n 12V and 42V Automotive and Heavy Equipment 48V Telecom Power Supplies Avionics and Industrial Control Systems Distributed Power Converters L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical Application 48W, 16VIN to 60VIN DC/DC µModule® Regulator 4.7µF ×2 VIN 1M 48.7k LTM8027 RUN BIAS1 SS BIAS2 SYNC AUX RT ADJ GND 100 VOUT 12V 4A VOUT 24VIN 90 80 22µF ×4 56.2k 3845 TA01a EFFICIENCY (%) VIN 16V TO 60V Efficiency vs Load 70 60 50 40 30 20 10 0 0 1 2 LOAD (A) 3 4 8027 TA01b 8027fb 1 LTM8027 Absolute Maximum Ratings Pin Configuration (Note 1) VIN Voltage.................................................................65V BIAS1.........................................................................15V BIAS2.........................................................................24V SYNC, ADJ, RT, RUN, SS Voltages...............................5V Current into RUN Pin (Note 2)...................................1mA VOUT, AUX..................................................................25V Current Out of AUX.............................................. 200mA Internal Operating Temperature (Note 3) E-, I-Grade.......................................... –40°C to 125°C MP-Grade........................................... –55°C to 125°C Maximum Soldering Temperature.......................... 245°C Storage Temperature Range................... –55°C to 125°C TOP VIEW 11 10 9 8 AUX 7 BIAS1 6 SS 5 RUN 4 BIAS2 3 ADJ 2 1 VOUT BANK 1 GND BANK 2 VIN BANK 3 A B C D E F G H J K L SYNC RT LGA PACKAGE 113-LEAD (15mm × 15mm × 4.32mm) TJMAX = 125°C, θJA = 12.2°C/W, θJC(TOP) = 9.3°C/W, θJC(BOTTOM) = 3.6°C/W, θJBOARD = 7.54°C/W θ VALUES DETERMINED PER JESD 51-9 WEIGHT = 2.6 GRAMS Order Information LEAD FREE FINISH TRAY PART MARKING PACKAGE DESCRIPTION LTM8027EV#PBF LTM8027EV#PBF LTM8027V 113-Lead (15mm × 15mm × 4.32mm) LGA –40°C to 125°C TEMPERATURE RANGE (Note 3) LTM8027IV#PBF LTM8027IV#PBF LTM8027V 113-Lead (15mm × 15mm × 4.32mm) LGA –40°C to 125°C LTM8027MPV#PBF LTM8027MPV#PBF LTM8027V 113-Lead (15mm × 15mm × 4.32mm) LGA –55°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. 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 l denotes the specifications which apply over the full internal operating The temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, BIAS1 = BIAS2 = 10V, RUN = 2V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VIN Input DC Voltage (Note 5) VOUT Maximum Output DC Voltage 0A < IOUT ≤ 4A, VIN = 48V IOUT Output DC Current VIN ≤ 60V, VOUT = 12V, (Note 4) VIN(START) Minimum Start Voltage ∆VOUT/∆VIN Line Regulation VOUT = 12V, 15V< VIN < 60V, ILOAD = 4A ∆VOUT/∆ILOAD Load Regulation VUVLO(RISING) Input Undervoltage Lockout Threshold (Rising) VUVLO(FALLING) Input Undervoltage Lockout Threshold (Falling) MIN l TYP 4.5 MAX 60 24 0 UNITS V V 4 A 7.5 V 0.2 % VOUT = 12V, VIN = 24V, 0A < ILOAD ≤ 4A 0.2 % (Note 5) 4.6 V (Note 5) 3.7 V 8027fb 2 LTM8027 Electrical Characteristics The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, BIAS1 = BIAS2 = 10V, RUN = 2V, unless otherwise noted. SYMBOL PARAMETER VADJ ADJ Voltage CONDITIONS MIN l IQ(VIN) Quiescent Current into IN VBIAS1 BIAS1 Undervoltage Lockout (Rising) BIAS1 Undervoltage Lockout (Falling) IBIAS1 Current into BIAS1 VBIAS2 TYP 1.224 1.215 VBIAS = VAUX, VOUT = 12VDC, No Load VRUN = 0V MAX UNITS 1.238 1.245 V V 39 9 mA µA 6.5 6 V V 25 25 mA µA Minimum BIAS2 Voltage 3 V IBIAS2 Current Into BIAS2 1 µA VBIAS1(MINOV) Minimum Voltage to Overdrive Internal Regulator (INTVCC) 8.5 V No Load RUN = 0V RFB Internal Feedback Resistor 499 kΩ VRUN(RISING) RUN Enable Voltage (Rising) 1.4 V VRUN(FALLING) RUN Enable Voltage (Falling) 1.2 V fSW Switching Frequency 100 500 kHz kHz RSYNC SYNC Input Resistance 40 kΩ VSYNC(TH) SYNC Voltage Threshold ISS Soft-Start Charging Current RT = 187kΩ RT = 23.7kΩ fSYNC = 350kHz 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 RUN pin is internally clamped to 5V. Note 3: The LTM8027E is guaranteed to meet performance specifications from 0°C to 125°C internal operating temperature. 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 LTM8027I is guaranteed to meet specifications over the full l 2.3 V 2 µA –40°C to 125°C internal operating temperature range. The LTM8027MP is guaranteed to meet specifications over the full –55°C to 125°C internal operating 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 maximum continuous output current may be derated by the LTM8027 junction temperature. Note 5: VIN voltages below the start-up threshold (7.5V) are only supported when BIAS1 is externally driven above 6.5V. 8027fb 3 LTM8027 Typical Performance Characteristics (TA = 25°C unless otherwise noted) 100 Efficiency vs Load, VOUT = 2.5V 100 80 80 70 70 40 30 5VIN 12VIN 24VIN 36VIN 20 10 0 0 1 2 LOAD (A) 60 50 40 5VIN 12VIN 24VIN 36VIN 48VIN 60VIN 30 20 10 0 4 3 0 1 2 LOAD (A) 50 40 Efficiency vs Load, VOUT = 8V 100 10 0 Efficiency vs Load, VOUT = 12V 100 80 80 70 70 70 40 30 12VIN 24VIN 36VIN 48VIN 60VIN 20 10 0 0 1 2 LOAD (A) 60 50 40 30 24VIN 36VIN 48VIN 60VIN 20 10 0 4 3 0 1 2 LOAD (A) 90 80 80 70 70 EFFICIENCY (%) 90 40 30 24VIN 36VIN 48VIN 60VIN 20 10 0 0 1 2 LOAD (A) 3 40 30 24VIN 36VIN 48VIN 60VIN 1 0 2 LOAD (A) 8027 G06 1.2 60 50 40 30 0 4 3 Input Current vs VIN Output Shorted 1.0 36VIN 48VIN 60VIN 10 8027 G07 50 0 Efficiency vs Load, VOUT = 24V 20 4 60 10 INPUT CURRENT (A) 100 50 Efficiency vs Load, VOUT = 15V 8027 G05 Efficiency vs Load, VOUT = 18V 60 4 3 20 4 3 8027 G04 100 2 LOAD (A) 90 EFFICIENCY (%) 90 80 50 1 0 8027 G03 90 60 12VIN 24VIN 36VIN 48VIN 60VIN 30 8027 G02 EFFICIENCY (%) EFFICIENCY (%) 60 20 4 3 8027 G01 100 EFFICIENCY (%) 80 50 Efficiency vs Load, VOUT = 5V 90 70 60 EFFICIENCY (%) 100 90 EFFICIENCY (%) EFFICIENCY (%) 90 Efficiency vs Load, VOUT = 3.3V 0 1 2 LOAD (A) 3 0.8 0.6 0.4 0.2 4 8027 G08 0 0 10 40 30 50 20 INPUT VOLTAGE (V) 60 70 8027 G09 8027fb 4 LTM8027 Typical Performance Characteristics (TA = 25°C unless otherwise noted) 3000 3500 5VIN 12VIN 24VIN 36VIN 2000 1500 1000 2500 2000 0 3 4 1600 1400 1200 1000 0 2 LOAD (A) 200 0 1 2 3 1500 1000 500 500 2 3 0 4 0 1 2 3 8027 G13 1500 1000 500 1 2 LOAD (A) 0 1 3 4 8027 G16 2 LOAD (A) 3 8027 G15 15.50 36VIN 48VIN 60VIN 15.00 2500 2000 1500 1000 0 14.50 14.00 13.50 13.00 36VIN 24VIN 12VIN 12.50 0 1 4 Bias Current vs Load, VOUT = 2.5V 500 0 1000 0 4 BIAS CURRENT (mA) 2000 0 1500 Input Current vs Load, VOUT = 24V 3000 INPUT CURRENT (mA) INPUT CURRENT (mA) 2500 2000 8027 G14 3500 24VIN 36VIN 48VIN 60VIN 3000 24VIN 36VIN 48VIN 60VIN LOAD (A) Input Current vs Load, VOUT = 18V 4 3 500 LOAD (A) 3500 2 LOAD (A) Input Current vs Load, VOUT = 15V 2500 INPUT CURRENT (mA) INPUT CURRENT (mA) INPUT CURRENT (mA) 1000 1 1 8027 G12 3000 24VIN 36VIN 48VIN 60VIN 2000 1500 0 0 8027 G11 2500 2000 0 0 4 Input Current vs Load, VOUT = 12V 12VIN 24VIN 36VIN 48VIN 60VIN 2500 600 LOAD (A) Input Current vs Load, VOUT = 8V 3000 800 400 8027 G10 3500 12VIN 24VIN 36VIN 48VIN 60VIN 1800 1000 500 1 2000 1500 500 0 Input Current vs Load, VOUT = 5V 5VIN 12VIN 24VIN 36VIN 48VIN 60VIN 3000 INPUT CURRENT (mA) 2500 INPUT CURRENT (mA) Input Current vs Load, VOUT = 3.3V INPUT CURRENT (mA) Input Current vs Load, VOUT = 2.5V 2 LOAD (A) 3 4 12.00 0 1 2 3 4 LOAD (A) 8027 G17 8027 G18 8027fb 5 LTM8027 Typical Performance Characteristics (TA = 25°C unless otherwise noted) Bias Current vs Load, VOUT = 3.3V Bias Current vs Load, VOUT = 5V 18.0 25.5 16.5 16.0 15.5 15.0 48VIN 36VIN 24VIN 12VIN 14.5 0 1 2 LOAD (A) 15.0 14.5 14.0 48VIN 36VIN 24VIN 12VIN 13.5 13.0 4 3 0 1 2 29.0 37 28.0 27.5 27.0 26.5 26.0 48VIN 36VIN 24VIN 25.5 1 42 34 33 32 41 40 39 38 37 48VIN 36VIN 24VIN 0 1 2 3 48VIN 36VIN 36 35 4 0 1 VIN (V) 34 48VIN 36VIN 3 4 LOAD (A) 8027 G25 6.0 10.0 5.9 9.8 5.8 9.6 5.7 9.4 5.6 9.2 5.5 5.4 9.0 8.8 5.3 8.6 5.2 8.4 5.1 8.2 5.0 0 1 2 LOAD (A) 4 Minimum VIN vs Load, VOUT = 8V VIN (V) 42 36 3 8027 G24 Minimum VIN vs Load, VOUT = 5V 38 2 LOAD (A) 8027 G23 44 4 8027 G21 LOAD (A) 40 3 43 35 30 4 3 2 44 31 46 BIAS CURRENT (mA) 0 Bias Current vs Load, VOUT = 18V 36 Bias Current vs Load, VOUT = 24V 2 22.0 4 LOAD (A) 8027 G22 1 48VIN 36VIN 24VIN 45 LOAD (A) 0 23.0 BIAS CURRENT (mA) BIAS CURRENT (mA) BIAS CURRENT (mA) 28.5 32 23.5 Bias Current vs Load, VOUT = 15V 38 2 24.0 8027 G20 29.5 1 24.5 LOAD (A) Bias Current vs Load, VOUT = 12V 0 25.0 22.5 3 8027 G19 25.0 BIAS CURRENT (mA) 15.5 17.0 BIAS CURRENT (mA) BIAS CURRENT (mA) 26.0 16.0 17.5 14.0 Bias Current vs Load, VOUT = 8V 3 4 8027 G26 8.0 0 1 2 LOAD (A) 3 4 8027 G27 8027fb 6 LTM8027 Typical Performance Characteristics (TA = 25°C unless otherwise noted) Minimum VIN vs Load, VOUT = 15V 19.0 15.5 18.5 15.0 18.0 14.5 17.5 14.0 16.5 13.0 16.0 12.5 15.5 0 1 2 3 15.0 4 24 23 22 17.0 13.5 12.0 Minimum VIN vs Load, VOUT = 18V VIN (V) 16.0 VIN (V) VIN (V) Minimum VIN vs Load, VOUT = 12V 20 19 0 2 1 3 0 1 3 35 30 28 25 26 20 VIN (V) 30 Minimum VIN vs VOUT, IOUT = 4A Minimum VIN vs Load, VOUT = –3.3V 9 8 7 6 15 22 10 20 5 18 0 4 8027 G30 VIN (V) Minimum VIN vs Load, VOUT = 24V 24 2 LOAD (A) 8027 G29 8027 G28 VIN (V) 18 4 LOAD (A) LOAD (A) 32 21 5 4 3 2 0 1 2 3 4 1 0 5 10 LOAD (A) 15 20 1 3 30 10 25 8 20 Minimum VIN vs Load, VOUT = –8V Minimum VIN vs Load, VOUT = –12V 50 45 40 35 15 4 10 2 5 0 0 4 8027 G33 VIN (V) Minimum VIN vs Load, VOUT = –5V 6 2 LOAD (A) 8027 G32 VIN (V) VIN (V) 0 VOUT (V) 8027 G31 12 0 25 30 25 20 15 10 5 0 1 2 LOAD (A) 3 4 8027 G34 0 1 2 LOAD (A) 3 4 8027 G35 0 0 1 2 LOAD (A) 3 4 8027 G36 8027fb 7 LTM8027 Typical Performance Characteristics (TA = 25°C unless otherwise noted) 42 45 36VIN 24VIN 12VIN 5VIN 32 27 22 17 12 50 60VIN 48VIN 36VIN 24VIN 12VIN 5VIN 40 TEMPERATURE RISE (°C) 37 TEMPERATURE RISE (°C) Temperature Rise vs Load, VOUT = 3.3V 35 30 25 20 15 10 30 25 20 15 10 5 2 0 0 2 3 4 0 1 LOAD (A) 2 4 3 80 50 40 30 20 10 0 90 60VIN 48VIN 36VIN 24VIN 16VIN 70 60 40 30 20 10 0 1 2 3 4 0 1 2 0 2 1 50 40 30 20 10 3 4 8027 G42 Temperature Rise vs Load, VOUT = 24V 60VIN 48VIN 36VIN 90 TEMPERATURE RISE (°C) TEMPERATURE RISE (°C) 20 LOAD (A) 100 60 0 30 8027 G41 60VIN 48VIN 36VIN 26VIN 80 40 LOAD (A) Temperature Rise vs Load, VOUT = 18V 70 50 0 4 3 8027 G40 90 70 60 10 LOAD (A) 100 60VIN 48VIN 36VIN 24VIN 20.5VIN 80 50 0 4 Temperature Rise vs Load, VOUT = 15V TEMPERATURE RISE (°C) 60 3 8027 G39 Temperature Rise vs Load, VOUT = 12V Temperature Rise vs Load, VOUT = 8V 60VIN 48VIN 36VIN 24VIN 12VIN 2 LOAD (A) 8027 G38 TEMPERATURE RISE (°C) 70 1 0 LOAD (A) 8027 G37 TEMPERATURE RISE (°C) 40 5 1 60VIN 48VIN 36VIN 24VIN 12VIN 35 7 0 Temperature Rise vs Load, VOUT = 5V 45 TEMPERATURE RISE (°C) Temperature Rise vs Load, VOUT = 2.5V 80 70 60 50 40 30 20 10 0 1 2 LOAD (A) 3 4 8027 G43 0 0 1 2 LOAD (A) 3 4 8027 G44 8027fb 8 LTM8027 Pin Functions VIN (Bank 3): The VIN pins supply current to the LTM8027’s internal regulator and to the internal power switch. These pins must be locally bypassed with an external, low ESR capacitor (see Table 2). VOUT (Bank 1): Power Output Pins. Apply the output filter capacitor and the output load between these and the GND pins. AUX (Pin A7): Low Current Voltage Source for BIAS1 and BIAS2. In many designs, the BIAS pin is connected to VOUT by way of the AUX pin. The AUX pin is internally connected to VOUT and is placed near the BIAS pins to ease printed circuit board routing. Although this pin is internally connected to VOUT, do NOT connect this pin to the load. If this pin is not tied to BIAS1 and BIAS2, leave it floating. BIAS1 (Pin A6): The BIAS1 pin connects to the internal power bus. Connect to a power source greater than 8.5V. If the output is greater than 8.5V, connect it to this pin. If the output voltage is less, connect this to a voltage source between 8.5V and 15V. BIAS2 (Pin A3): Internal Biasing Power. Connect to AUX (if 24V or less) or a voltage source above 3V. Do not leave BIAS2 floating. RUN (Pin A4): Tie the RUN pin to ground to shut down the LTM8027. Tie to 1.4V or more for normal operation. The RUN pin is internally clamped to 5V, so when it is pulled up, be sure to use a pull-up resistor that limits the current in to the RUN pin to less than 1mA. If the shutdown feature is not used, tie this pin to the VIN pin through a pull-up resistor. GND (Bank 2): Tie these GND pins to a local ground plane below the LTM8027 and the circuit components. RT (Pin B1): The RT pin is used to program the switching frequency of the LTM8027 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. SYNC (Pin C1): The SYNC pin provides an external clock input for synchronization of the internal oscillator. The RT resistor should be set such that the internal oscillator frequency is 10% to 25% below the external clock frequency. This external clock frequency must be between 100kHz and 500kHz. If unused, the SYNC pin is connected to GND. For more information see Oscillator Sync in the Application Information section of this data sheet. ADJ (Pin A2): The LTM8027 regulates its ADJ pin to 1.23V. Connect the adjust resistor from this pin to ground. The value of RADJ is given by the equation: RADJ = 613.77/(VOUT – 1.23) where RADJ is in kΩ. SS (Pin A5): The soft-start pin is used to program the supply soft-start function. Use the following formula to calculate CSS for a given output voltage slew rate: CSS = 2µA(tSS/1.231V) The pin should be left unconnected when not using the soft-start function. 8027fb 9 LTM8027 Block Diagram VIN VOUT 6.8µH 499k 4.7pF 2.2µF RUN SS INTERNAL CONNECTION TO VOUT CURRENT MODE CONTROLLER SYNC VIN GND INTERNAL LINEAR REGULATOR RT AUX BIAS1 INTVCC BIAS2 ADJ 8027 BD Operation The LTM8027 is a standalone nonisolated step-down switching DC/DC power supply with an input voltage range of 4.5V to 60V that can deliver up to 4A of output current. This module provides a precisely regulated output voltage up to 24V, programmable via one external resistor. Given that the LTM8027 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 above. The LTM8027 contains a current mode controller, power switching element, power inductor, power MOSFETs and a modest amount of input and output capacitance. The LTM8027 is a fixed frequency PWM regulator. The switching frequency is set by simply connecting the appropriate resistor from the RT pin to GND. A linear regulator provides internal power (shown as INTVCC on the Block Diagram) to the control circuitry. The bias regulator normally draws power from the VIN pin, but if the BIAS1 pin is connected to an external voltage higher than 8.5V, bias power will be drawn from the external source (typically the regulated output voltage). This improves efficiency. The RUN pin is used to enable or place the LTM8027 in shutdown, disconnecting the output and reducing the input current to less than 9µA. 8027fb 10 LTM8027 Applications Information For most applications, the design process is straight forward, summarized as follows: 1.Look at Table 2 and find the row that has the desired input range and output voltage. 2.Apply the recommended CIN, COUT, RADJ and RT values. 3.Connect the BIAS pins as indicated. While these component and connection 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. Capacitor Selection Considerations The CIN and COUT capacitor values in Table 2 are the minimum recommended values for the associated operating conditions. Applying capacitor values below those indicated in Table 2 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. 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. A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LTM8027. A ceramic input capacitor combined with trace or cable inductance forms a high Q (under damped) tank circuit. If the LTM8027 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. Input Power Requirements The LTM8027 is biased using an internal linear regulator to generate operational voltages from the VIN pin. Virtually all of the circuitry in the LTM8027 is biased via this internal linear regulator output (INTVCC on the Block Diagram). This pin is internally decoupled with a low ESR capacitor to GND. The INTVCC regulator generates an 8V output provided there is ample voltage on the VIN pin. The INTVCC regulator has approximately 1V of dropout, and will follow the VIN pin with voltages below the dropout threshold. The LTM8027 has a typical start-up requirement of VIN > 7.5V. This assures that the onboard regulator has ample headroom to bring the internal regulator (INTVCC) above its UVLO threshold. The INTVCC regulator can only source current, so forcing the BIAS1 pin above 8.5V allows use of externally derived power for the IC. This effectively shuts down the internal linear regulator and reduces power dissipation within the LTM8027. Using the onboard regulator for start-up, then applying power to BIAS1 from the converter output or external supply maximizes conversion efficiencies and is a common practice. If IBIAS1 is maintained above 6.5V using an external source, the LTM8027 can continue to operate with VIN as low as 4.5V. BIAS Power The internal circuitry of the LTM8027 is powered by the INTVCC bus, which is derived either from the afore mentioned internal linear regulator or the BIAS1 pin, if it is greater than 8.5V. Since the internal linear regulator is by nature dissipative, deriving INTVCC from an external source through the BIAS pins reduces the power lost within the LTM8027 and can increase overall system efficiency. 8027fb 11 LTM8027 Applications Information PINTVCC = (VIN – 8) • IINTVCC or only 60mW. This has a small but probably acceptable effect on the operating temperature of the LTM8027. If the input rises to 60V, however, the power dissipation is a lot higher, over 780mW. This can cause unnecessarily high junction temperatures if the INTVCC regulator must dissipate this amount of power for very long. Connect BIAS2 to AUX (if 24V or less) or a voltage source above 3V. Soft-Start The soft-start function controls the slew rate of the power supply output voltage during start-up. A controlled output voltage ramp minimizes output voltage overshoot, reduces inrush current from the VIN supply, and facilitates supply sequencing. A capacitor connected from the SS pin to GND programs the slew rate. The capacitor is charged from an internal 2µA current source producing a ramped voltage that overrides the command reference to the controller, resulting in a smooth output voltage ramp. The soft-start circuit is disabled once the SS pin voltage has been charged to 200mV above the internal reference of 1.231V. During a VIN UVLO, RUN event, or undervoltage on internal bias, the SS pin voltage is discharged with a 50µA current. Therefore, the value of the SS capacitor determines how long one of these events must be in order to completely discharge the soft-start capacitor. In the case of an output overload or short circuit, the SS pin voltage is clamped to a diode drop above the ADJ pin. Once the short has been removed the VADJ pin voltage starts to recover. The softstart circuit takes control of the output voltage slew rate once the VADJ pin voltage has exceeded the slowly ramp- ing SS pin voltage, reducing the output voltage overshoot during a short-circuit recovery. The desired soft-start time (tSS) is programmed via the CSS capacitor as follows: CSS = 2µA • tSS 1.231V The amount of time in which the power supply must be under a VIN, internal regulator (INTVCC) or VSHDN UVLO fault condition (tFAULT) before the SS pin voltage enters its active region is approximated by the following formula: CSS • 0.65V 50µA tFAULT = Operating Frequency Trade-offs The LTM8027 uses a constant frequency architecture that can be programmed over a 100kHz to 500kHz range with a single resistor from the RT pin to ground. The nominal voltage on the RT pin is 1V and the current that flows from this pin is used to charge an internal oscillator capacitor. The value of RT for a given operating frequency can be chosen from Figure 1 or Table 1. 600 500 FREQUENCY (kHz) For example, suppose the LTM8027 needs to provide 5V from an input voltage source that is nominally 12V. From Table 2, the recommended RT value is 162k, which corresponds to an operating frequency of 210kHz. From the graphs in the Typical Performance Characteristics, the typical internal regulator (INTVCC) current at 12VIN and 210kHz is 15mA. The power dissipated by the internal linear regulator at 12VIN is given by the equation: 400 300 200 100 0 0 50 100 RT (kΩ) 150 200 8027 F01 Figure 1. Timing Resistor (RT) Value 8027fb 12 LTM8027 Applications Information Table 1 lists typical resistor values for common operating frequencies. Table 1. RT Resistor Values vs Frequency RT (kΩ) fSW (kHz) 187 100 118 150 82.5 200 63.4k 250 48.7k 300 40.2k 350 31.6k 400 27.4k 450 23.7k 500 It is recommended that the user apply the RT value given in Table 2 for the input and output operating condition. System level or other considerations, however, may necessitate another operating frequency. While the LTM8027 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 damage the LTM8027 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. The maximum frequency (fMAX) at which the LTM8027 should be allowed to switch and the minimum frequency set resistor value that should be used for a given set of input and output operating condition is given in Table 2 as RT(MIN). There are additional conditions that must be satisfied if the synchronization function is used. Please refer to the Synchronization section for details. Output Voltage Programming The LTM8027 regulates its ADJ pin to 1.23V. Connect the adjust resistor from this pin to ground. The value of RADJ is given by the equation RADJ = 613.77/(VOUT – 1.23), where RADJ is in kΩ. RUN Control The LTM8027 RUN pin uses a reference threshold of 1.4V. This precision threshold allows use of the RUN pin for both logic-level controlled applications and analog monitoring applications such as power supply sequencing. The LTM8027 operational status is primarily controlled by a UVLO circuit on internal power source. When the LTM8027 is enabled via the RUN pin, only the internal regulator (INTVCC) is enabled. Switching remains disabled until the UVLO threshold is achieved at the BIAS1 pin, when the remainder of the LTM8027 is enabled and switching commences. Because the LTM8027 high power converter is a power transfer device, a voltage that is lower than expected on the input supply could require currents that exceed the sourcing capabilities of that supply, causing the system to lock up in an undervoltage state. Input supply startup protection can be achieved by enabling the RUN pin using a resistive divider from the VIN supply to ground. Setting the divider output to 1.4V when that supply is at an adequate voltage prevents an LTM8027 converter from drawing large currents until the input supply is able to provide the required power. 200mV of input hysteresis on the RUN pin allows for about 15% of input supply droop before disabling the converter. Input UVLO and RUN The RUN pin has a precision voltage threshold with hysteresis which can be used as an undervoltage lockout threshold (UVLO) for the power supply. Undervoltage lockout keeps the LTM8027 in shutdown until the supply input voltage is above a certain voltage programmed by the user. The hysteresis voltage prevents noise from falsely tripping UVLO. Resistors are chosen by first selecting RB (refer to Figure 2). Then: VIN(ON) RA = RB • – 1 1.4V where VIN(ON) is the input voltage at which the undervoltage lockout is disabled and the supply turns on. 8027fb 13 LTM8027 Applications Information VSUPPLY RA RUN PIN RB 8027 F02 Figure 2. Undervoltage Lockout Resistive Divider Example: Select RB = 49.9k, VIN(ON) = 14.5V (based upon a 15V minimum input voltage) 14.5V RA = 49.9k • – 1 = 464k 1.4V The VIN turn off voltage is 15% below turn on. In the example the VIN(OFF) would be 12.3V. The shutdown function can be disabled by connecting the RUN pin to the VIN pin through a large value pull-up resistor, (RPU). This pin contains a low impedance clamp at 6V, so the RUN pin will sink current from the RPU pull-up resistor: V – 6V IRUN = IN RPU Because this arrangement will clamp the RUN pin to 6V, it will violate the 5V absolute maximum voltage rating of the pin. This is permitted, however, as long as the absolute maximum input current rating of 1mA is not exceeded. Input RUN pin currents of <100µA are recommended: a 1M or greater pull-up resistor is typically used for this configuration. Hot-Plugging Safely The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of LTM8027. However, these capacitors can cause problems if the LTM8027 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 under damped tank circuit, and the voltage at the VIN pin of the LTM8027 can ring to twice the nominal input voltage, possibly exceeding the LTM8027’s rating and damaging the part. If the input supply is poorly controlled or the user will be plugging the LTM8027 into an energized supply, the input network should be designed to prevent this overshoot by introducing a damping element into the path of current flow. This is often done by adding an inexpensive electrolytic bulk capacitor across the input terminals of the LTM8027. The criteria for selecting this capacitor is that the ESR is high enough to damp the ringing, and the capacitance value is several times larger than the LTM8027 ceramic input capacitor. The bulk capacitor does not need to be located physically close to the LTM8027; it should be located close to the application board’s input connector, instead. Synchronization The oscillator can be synchronized to an external clock. Choose the RT resistor such that the resultant frequency is at least 10% below the desired synchronization frequency. It is recommended that the SYNC pin be driven with a square wave that has amplitude greater than 2.3V, pulse width greater than 1µs and rise time less than 500ns. The rising edge of the sync wave form triggers the discharge of the internal oscillator capacitor. PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8027. The LTM8027 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. 8027fb 14 LTM8027 Applications Information VOUT COUT COUT GND AUX BIAS1 SS RUN CIN BIAS2 VIN RADJ GND RT 8027 F03 SYNC Figure 3. Suggested Layout Ensure that the grounding and heat sinking are acceptable. A few rules to keep in mind are: 1.Place the RADJ and RT resistors 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 LTM8027. 3.Place the COUT capacitor as close as possible to the VOUT and GND connection of the LTM8027. 4.Place the CIN and COUT capacitors such that their ground current flow directly adjacent to or underneath the LTM8027. 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 LTM8027. 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 LTM8027 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. Thermal Considerations The LTM8027 output current may need to be derated if it is required to operate in a high ambient temperature or deliver a large amount of continuous power. The amount of current derating is dependent upon the input voltage, output power and ambient temperature. The temperature rise curves given in the Typical Performance Characteristics section can be used as a guide. These curves were generated by a LTM8027 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. 8027fb 15 LTM8027 Applications Information The junction-to-air and junction-to-board thermal resistances given in the Pin Configuration diagram may also be used to estimate the LTM8027 internal temperature. These thermal coefficients are determined per JESD 51-9 (JEDEC standard, test boards for area array surface mount package thermal measurements) through analysis and physical correlation. Bear in mind that the actual thermal resistance of the LTM8027 to the printed circuit board depends upon the design of the circuit board. The die temperature of the LTM8027 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 LTM8027. The bulk of the heat flow out of the LTM8027 is through the bottom of the module and the LGA 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. Table 2. Recommended Component Values and Configuration (TA = 25°C. See Typical Performance Characteristics for load Conditions) VIN RANGE (V) VOUT (V) BIAS1 RADJ (kΩ) fOPTIMAL (kHz) 4.5 to 60 3.3 7.5 to 60 5 2 × 4.7µF 2220 100V 5 × 100µF 1812 6.3V 8.5V to 15V 301 115 154 160 107 2 × 4.7µF 2220 100V 4 × 100µF 1210 6.3V 8.5V to 15V 162 210 75.0 230 68.2 10.5 to 60 8 2 × 4.7µF 2220 100V 4 × 47µF 1210 10V 8.5V to 15V 90.9 260 59.0 350 40.2 2 × 4.7µF 2220 100V 4 × 22µF 1210 16V AUX 56.2 300 48.7 500 23.7 44.2 350 40.2 500 23.7 CIN COUT ROPTIMAL (kΩ) fMAX (kHz) RMAX (kΩ) 16 to 60 12 20.5 to 60 15 2 × 4.7µF 2220 100V 4 × 22µF 1210 16V AUX 26 to 60 18 2 × 4.7µF 2220 100V 4 × 10µF 1812 25V 8.5V to 15V 36.5 400 31.6 500 23.7 34 to 60 24 2 × 4.7µF 2220 100V 4 × 10µF 1812 25V 8.5V to 15V 26.7 430 28.7 500 23.7 4.5 to 40 2.5 2 × 10µF 2220 50V 5 × 100µF 1812 6.3V 8.5V to 15V 487 145 124 185 88.7 4.5 to 40 3.3 2 × 10µF 2220 50V 4 × 100µF 1812 6.3V 8.5V to 15V 301 165 102 240 64.9 7.5 to 40 5 2 × 10µF 2220 50V 4 × 100µF 1210 6.3V 8.5V to 15V 162 210 75.0 315 45.3 10.5 to 40 8 2 × 10µF 2220 50V 4 × 47µF 1210 10V 8.5V to 15V 90.9 260 59.0 500 23.7 16 to 40 12 2 × 10µF 2220 50V 4 × 22µF 1210 16V AUX 56.2 300 48.7 500 23.7 20.5 to 40 15 1 × 10µF 2220 50V 4 × 22µF 1210 16V AUX 44.2 350 40.2 500 23.7 26 to 40 18 1 × 10µF 2220 50V 4 × 10µF 1812 25V 8.5V to 15V 36.5 400 31.6 500 23.7 34 to 40 24 1 × 10µF 2220 50V 4 × 10µF 1812 25V 8.5V to 15V 26.7 430 28.7 500 23.7 4.5 to 56 –3.3 2 × 4.7µF 2220 100V 5 × 100µF 1812 6.3V 8.5V to 15V Above Output 301 115 154 155 115 4.5 to 55 –5 2 × 4.7µF 2220 100V 4 × 100µF 1210 6.3V 8.5V to 15V Above Output 162 190 90.9 230 68.2 10.5 to 52 –8 2 × 4.7µF 2220 100V 4 × 47µF 1210 10V 8.5V to 15V Above Output 90.9 260 59.0 350 40.2 16 to 48 –12 2 × 4.7µF 2220 100V 4 × 22µF 1210 16V AUX 56.2 300 48.7 500 23.7 8027fb 16 LTM8027 Typical Applications 3.3V VOUT Step-Down Converter VIN* 4.5V TO 40V 10µF ×2 VIN 1M VOUT 3.3V 4A VOUT LTM8027 RUN BIAS1 SS BIAS2 100µF ×4 AUX SYNC RT ADJ GND 102k 9V 301k *RUNNING VOLTAGE. SEE APPLICATIONS INFORMATION FOR START-UP DETAILS 3845 TA02 5V VOUT Step-Down Converter VIN 7.5V TO 60V 4.7µF ×2 VIN 1M LTM8027 RUN BIAS1 SS BIAS2 9V 100µF ×4 AUX SYNC RT 75k VOUT 5V 4A VOUT ADJ GND 162k 3845 TA03 8027fb 17 LTM8027 TYPICAL Applications 18V VOUT Step-Down Converter VIN 26V TO 60V 4.7µF ×2 VIN 1M VOUT 18V 3A 4A SURGE VOUT LTM8027 RUN BIAS1 SS BIAS2 9V 10µF ×4 AUX SYNC RT ADJ GND 31.6k 36.5k 3845 TA05 –12V VOUT Positive-to-Negative Converter VIN 20V TO 48V 4.7µF ×2 VIN 1M VOUT LTM8027 RUN BIAS1 SS BIAS2 RT 48.7k 22µF ×4 AUX SYNC ADJ GND 56.2k 3845 TA07 SCHOTTKY DIODE OPTIONAL VOUT –12V 3A Package Photograph 8027fb 18 4 2.540 SUGGESTED PCB LAYOUT TOP VIEW 2.540 3.810 5.080 6.350 X 15 BSC Y DETAIL A 0.27 – 0.37 SUBSTRATE eee S X Y DETAIL B 0.635 ±0.025 SQ. 113x aaa Z 3.95 – 4.05 MOLD CAP DETAIL B 4.22 – 4.42 6. THE TOTAL NUMBER OF PADS: 113 SYMBOL TOLERANCE aaa 0.15 bbb 0.10 eee 0.05 5. PRIMARY DATUM -Z- IS SEATING PLANE 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 4 6.350 LAND DESIGNATION PER JESD MO-222, SPP-010 3 5.080 3.810 2.540 1.270 1.27 BSC 12.70 BSC 3 L TRAY PIN 1 BEVEL COMPONENT PIN “A1” PADS SEE NOTES 2. ALL DIMENSIONS ARE IN MILLIMETERS 3.810 0.000 5.080 NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 6.350 (Reference LTC DWG # 05-08-1756 Rev Ø) Z 1.270 2.540 3.810 5.080 6.350 PACKAGE TOP VIEW 1.270 PAD 1 CORNER 15 BSC 0.000 aaa Z 1.270 // bbb Z LGA Package 113-Lead (15mm × 15mm × 4.32mm) K J G F E D C B LGA 113 0807 REV Ø A DETAIL A PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX µModule PACKAGE BOTTOM VIEW H 12.70 BSC 1 2 3 4 5 6 7 8 9 C(0.30) PAD 1 10 11 LTM8027 Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. Package Description 8027fb 19 LTM8027 Package Description Pin Assignment Table (Arranged by Pin Number) PIN NAME PIN NAME PIN NAME A1 GND D6 GND H5 GND A2 ADJ D7 GND H6 GND A3 BIAS2 D8 GND H7 GND A4 RUN D9 GND H8 GND A5 SS D10 GND H9 VOUT A6 BIAS1 D11 GND H10 VOUT A7 AUX E1 GND H11 VOUT A8 GND E2 GND J1 VIN A9 GND E3 GND J2 VIN A10 GND E4 GND J3 VIN A11 GND E5 GND J5 GND B1 RT E6 GND J6 GND B2 GND E7 GND J7 GND B3 GND E8 GND J8 GND B4 GND E9 VOUT J9 VOUT B5 GND E10 VOUT J10 VOUT B6 GND E11 VOUT J11 VOUT B7 GND F1 GND K1 VIN B8 GND F2 GND K2 VIN B9 GND F3 GND K3 VIN B10 GND F4 GND K5 GND B11 GND F5 GND K6 GND C1 SYNC F6 GND K7 GND C2 GND F7 GND K8 GND C3 GND F8 GND K9 VOUT C4 GND F9 VOUT K10 VOUT C5 GND F10 VOUT K11 VOUT C6 GND F11 VOUT L1 VIN C7 GND G5 GND L2 VIN C8 GND G6 GND L3 VIN C9 GND G7 GND L5 GND C10 GND G8 GND L6 GND C11 GND G9 VOUT L7 GND D1 GND G10 VOUT L8 GND D2 GND G11 VOUT L9 VOUT D3 GND H1 VIN L10 VOUT D4 GND H2 VIN L11 VOUT D5 GND H3 VIN 8027fb 20 LTM8027 Revision History REV DATE DESCRIPTION PAGE NUMBER A 1/11 Changed Shutdown Current Supply to 9µA in Features. 1 Updated Absolute Maximum Ratings section. 2 Updated VBIAS1(MINOV) and Note 3 in Electrical Characteristics section. 3 Replaced graph 9. 4 Updated Pin Functions section. B 9/11 9 Text edits to Applications Information. 11-16 Updated Typical Applications. 17, 18 Updated Related Parts. 22 Added (Note 3) notation to the Order Information section. 2 Updated minimum spec for VBIAS2. 3 Updated descriptions for AUX and BIAS2 in the Pin Functions section. 9 Updated text in the Input Power Requirements section. 11 Added text to end of the BIAS Power section. 12 8027fb 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. 21 LTM8027 Typical Application 15V VOUT Step-Down Converter VIN 20.5V TO 60V 4.7µF ×2 VIN VOUT 15V 3.5A 4A SURGE VOUT 1M LTM8027 RUN BIAS1 SS BIAS2 RT 40.2k 22µF ×4 AUX SYNC ADJ GND 44.2k 3845 TA04 Related Parts PART NUMBER DESCRIPTION COMMENTS LTM4600 10A DC/DC µModule Regulator 10A DC/DC Step-Down µModule Regulator, 15mm × 15mm × 2.8mm LGA LTM4600HVMPV Military Plastic 10A DC/DC µModule Regulator –55°C to 125°C Operation, 15mm × 15mm × 2.8mm LGA LTM4601/ LTM4601A 12A DC/DC µModule Regulator with PLL, Output Tracking/Margining and Remote Sensing Synchronizable, PolyPhase Operation, LTM4601-1 Version has no Remote Sensing LTM4602 20V, 6A DC/DC µModule Regulator Pin Compatible with the LTM4600 LTM4603 6A DC/DC µModule with PLL and Output Tracking/ Margining and Remote Sensing Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote Sensing, Pin Compatible with the LTM4601 LTM4604A 4A Low VIN DC/DC µModule Regulator 2.375V ≤ VIN ≤ 5V, 0.8V ≤ VOUT ≤ 5V, 9mm × 15mm × 2.3mm LGA LTM4608A 8A Low VIN DC/DC µModule Regulator 2.7V ≤ VIN ≤ 5V, 0.6V ≤ VOUT ≤ 5V, 9mm × 15mm × 2.8mm LGA LTM8020 200mA, 36V DC/DC µModule Regulator Fixed 450kHz Frequency, 1.25V ≤ VOUT ≤ 5V, 6.25mm × 6.25mm × 2.32mm LGA LTM8022 1A, 36V DC/DC µModule Regulator Adjustable Frequency, 0.8V ≤ VOUT ≤ 5V, 9mm × 11.25mm × 2.82mm LGA, Pin Compatible to the LTM8023 LTM8023 2A, 36V DC/DC µModule Regulator Adjustable Frequency, 0.8V ≤ VOUT ≤ 5V, 9mm × 11.25mm × 2.82mm LGA, Pin Compatible to the LTM8022 LTM8025 3A, 36V DC/DC µModule Regulator 0.8V ≤ VOUT ≤ 24V, 9mm × 15mm × 4.32mm LGA 8027fb 22 Linear Technology Corporation LT 0911 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2009