LTM8026 36VIN, 5A CVCC Step-Down µModule Regulator Features Description Complete Step-Down Switch Mode Power Supply Constant-Voltage Constant-Current Operation Selectable Output Current Up to 5A Parallelable for Increased Output Current, Even from Different Voltage Sources n Wide Input Voltage Range: 6V to 36V n1.2V to 24V Output Voltage n Selectable Switching Frequency: 100kHz to 1MHz n(e4) RoHS Compliant Package with Gold Pad Finish n Programmable Soft-Start n Tiny, Low Profile (11.25mm × 15mm × 2.82mm) Surface Mount LGA Package The LTM®8026 is a 36VIN, 5A constant-voltage, constantcurrent (CVCC) step-down µModule® regulator. Included in the package are the switching controller, power switches, inductor and support components. Operating over an input voltage range of 6V to 36V, the LTM8026 supports an output voltage range of 1.2V to 24V. CVCC operation allows the LTM8026 to accurately regulate its output current up to 5A over the entire output range. The output current can be set by a control voltage, a single resistor or a thermistor. Only resistors to set the output voltage and frequency and the bulk input and output filter capacitors are needed to finish the design. n n n n The low profile package (2.82mm) enables utilization of unused space on the bottom of PC boards for high density point-of-load regulation. The LTM8026 is packaged in a thermally-enhanced, compact (11.25mm × 15mm) and low profile (2.82mm) overmolded land grid array (LGA) package suitable for automated assembly by standard surface mount equipment. The LTM8026 is RoHS compliant. Applications SuperCap Charging General Purpose Industrial n Extreme Short-Circuit Protection or Accurate Output Current Limit nµController-Based Battery Charging n High Power LED Drive n Multiple Input, Single Output Voltage Conversion n n L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 7199560, 7321203 and others pending. Typical Application Typical Application 10µF 100k VIN RUN SS VREF SYNC CTL_I COMP CTL_T GND ADJ RT 90.9k 3.0 VOUT 2.5V 5A LTM8026 VOUT 100µF + 330µF 9.09k 2.5 OUTPUT VOLTAGE (V) VIN 6V TO 36V VOUT vs IOUT, 12VIN 2.0 1.5 1.0 0.5 8026 TA01a 0 0 1 2 3 4 5 OUTPUT CURRENT (A) 6 8026 TA01b 8026fa 1 LTM8026 ADJ SS COMP RT TOP VIEW VREF VIN.............................................................................40V ADJ, RT, COMP, CTL_I, CTL_T, VREF............................3V VOUT...........................................................................25V RUN, SYNC, SS............................................................6V Current Into RUN Pin.............................................100µA Internal Operating Temperature Range... –40°C to 125°C Solder Temperature................................................ 250°C Storage Temperature.............................. –55°C to 125°C Pin Configuration CLT_I (Note 1) CLT_T Absolute Maximum Ratings 8 7 SYNC BANK 2 GND 6 RUN 5 4 BANK 1 3 BANK 3 VOUT 2 VIN 1 A B C D E F G H J K L LGA PACKAGE 81-LEAD (15mm × 11.25mm × 2.82mm) TJMAX = 125°C, θJA = 18.6°C/W, θJC(bottom) = 5.4°C/W, θJB = 5.6°C/W, θJC(top) = 10.8°C/W WEIGHT = 1.4g, θ VALUES DERIVED FROM A 4-LAYER 7.62cm × 7.62cm Order Information LEAD FREE FINISH TRAY PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE (NOTE 3) LTM8026EV#PBF LTM8026EV#PBF LTM8026V 81-Lead (15mm × 11.25mm × 2.82mm) LGA –40°C to 125°C LTM8026IV#PBF LTM8026IV#PBF LTM8026V 81-Lead (15mm × 11.25mm × 2.82mm) LGA –40°C to 125°C LTM8026MPV#PBF LTM8026MPV#PBF LTM8026V 81-Lead (15mm × 11.25mm × 2.82mm) LGA –55°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ This product is only offered in trays. For more information go to: http://www.linear.com/packaging/ 8026fa 2 LTM8026 Electrical Characteristics The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25°C. RUN = 3V, unless otherwise noted. (Note 3) PARAMETER CONDITIONS MIN Minimum Input Voltage TYP MAX 6 l UNITS V Output DC Voltage IOUT = 1A, RADJ Open IOUT = 1A, RADJ = 499Ω Output DC Current 6V < VIN < 36V, VOUT = 3.3V Quiescent Current Into VIN RUN = 0V No Load 0.1 2 Line Regulation 6V < VIN < 36V, IOUT = 1A 0.1 Load Regulation VIN = 12V, 0A < IOUT < 5A 0.7 % Output RMS Voltage Ripple VIN = 12V, IOUT = 4.5A 10 mV Switching Frequency RT = 40.2k RT = 453k 1000 100 kHz kHz Voltage at ADJ Pin 1.2 24 0 l 1.16 1.19 V V 5 A 3 4 µA mA % 1.22 V Current Out of ADJ Pin ADJ = 0V, VOUT = 1V 100 µA RUN Pin Current RUN = 1.45V 5.5 µA RUN Threshold Voltage (Falling) 1.47 RUN Input Hysteresis 1.55 CTL_I Control Range 0 CTL_I Pin Current CTL_I Current Limit Accuracy CTL_I = 1.5V CTL_I = 0.75V CTL_T Control Range 5.1 2.24 5.6 2.8 0 CTL_T Pin Current CTL_T Current Limit Accuracy 1.63 130 CTL_T = 1.5V CTL_T = 0.75V 5.1 2.24 VREF Voltage 0.5mA Load 1.89 SS Pin Current (Note 4) SYNC Input Low Threshold fSYNC = 400kHz SYNC Input High Threshold fSYNC = 400kHz SYNC Bias Current SYNC = 0V 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: This µModule regulator includes overtemperature protection that is intended to protect the device during momentary overload conditions. Internal temperature will exceed 125°C when overtemperature protection is active. Continuous operation above the specified maximum internal operating junction temperature may impair device reliability. 5.6 2.8 V mV 1.5 V 1.5 µA 6.1 3.36 A A 1.5 V 1.5 µA 6.1 3.36 A A 2.04 –11 V µA 0.6 1.2 V V 1 µA Note 3: The LTM8026E 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 LTM8026I is guaranteed to meet specifications over the full –40°C to 125°C internal operating temperature range. The LTM8026MP is guaranteed to meet specifications over the full –55°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: Current flows out of pin. 8026fa 3 LTM8026 Typical Performance Characteristics TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable. 1.5VOUT Efficiency vs Output Current 90 85 85 85 80 80 80 70 65 60 50 0 1 2 4 3 OUTPUT CURRENT (A) 75 70 65 60 6VIN 12VIN 24VIN 36VIN 55 EFFICIENCY (%) 90 75 55 50 5 0 1 2 4 3 OUTPUT CURRENT (A) 70 65 55 50 5 95 90 85 80 80 80 6VIN 12VIN 24VIN 36VIN 55 50 0 1 2 4 3 OUTPUT CURRENT (A) EFFICIENCY (%) 90 85 EFFICIENCY (%) 90 60 75 70 65 6VIN 12VIN 24VIN 36VIN 60 55 50 5 0 1 2 4 3 OUTPUT CURRENT (A) 8026 G04 90 EFFICIENCY (%) 80 75 70 65 50 0 1 2 4 3 OUTPUT CURRENT (A) 50 5 8026 G07 0 1 2 4 3 OUTPUT CURRENT (A) 18VOUT Efficiency vs Output Current 100 90 95 85 90 80 75 60 5 8026 G06 95 85 80 75 65 5 12VIN 24VIN 36VIN 55 70 12VIN 24VIN 36VIN 55 65 60 EFFICIENCY (%) 95 60 75 12VOUT Efficiency vs Output Current 100 5 70 8026 G05 8VOUT Efficiency vs Output Current 85 2 4 3 OUTPUT CURRENT (A) 95 85 65 1 5VOUT Efficiency vs Output Current 95 75 0 8026 G03 3.3VOUT Efficiency vs Output Current 70 6VIN 12VIN 24VIN 36VIN 8026 G02 2.5VOUT Efficiency vs Output Current EFFICIENCY (%) 75 60 6VIN 12VIN 24VIN 36VIN 8026 G01 EFFICIENCY (%) 1.8VOUT Efficiency vs Output Current 90 EFFICIENCY (%) EFFICIENCY (%) 1.2VOUT Efficiency vs Output Current 70 24VIN 36VIN 0 1 2 4 3 OUTPUT CURRENT (A) 5 8026 G08 65 24VIN 36VIN 0 1 2 4 3 OUTPUT CURRENT (A) 5 8026 G09 8026fa 4 LTM8026 Typical Performance Characteristics TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable. 24VOUT Efficiency vs Output Current –3.3VOUT Efficiency vs Output Current 90 EFFICIENCY (%) EFFICIENCY (%) 95 85 80 –5VOUT Efficiency vs Output Current 90 90 85 85 80 80 EFFICIENCY (%) 100 75 70 65 60 75 70 1 2 4 3 OUTPUT CURRENT (A) 50 5 0 1 4 3 OUTPUT CURRENT (A) 1.6 1 2 4 3 OUTPUT CURRENT (A) 80 75 70 65 60 5 0 0.5 1 1.5 2 2.5 1.6 1 0.6 1.0 0.6 0.2 0 5 6VIN 12VIN 24VIN 36VIN 2.5 0.8 0.4 8026 G16 3.0 1.2 0.2 5 2 4 3 OUTPUT CURRENT (A) Input Current vs Output Current 2.5VOUT 1.4 0.4 4 3 OUTPUT CURRENT (A) 0 8026 G15 INPUT CURRENT (A) 0.8 2 0.6 0 3.5 3 6VIN 12VIN 24VIN 36VIN 1.8 INPUT CURRENT (A) INPUT CURRENT (A) 2.0 1.0 1 0.8 Input Current vs Output Current 1.8VOUT 1.2 0 1.0 8026 G14 6VIN 12VIN 24VIN 36VIN 1.4 1.2 OUTPUT CURRENT (A) Input Current vs Output Current 1.5VOUT 1.6 5 0.2 12VIN 24VIN 8026 G13 1.8 2 4 3 OUTPUT CURRENT (A) 0.4 12VIN 24VIN 28VIN 0 INPUT CURRENT (A) EFFICIENCY (%) EFFICIENCY (%) 65 1 6VIN 12VIN 24VIN 36VIN 1.4 85 70 0 Input Current vs Output Current 1.2VOUT 80 75 12VIN 24VIN 31VIN 8026 G12 90 85 0 50 5 –12VOUT Efficiency vs Output Current 90 50 65 8026 G11 –8VOUT Efficiency vs Output Current 55 70 55 2 8026 G10 60 75 60 12VIN 24VIN 33VIN 55 28VIN 36VIN 0 TA = 25°C, unless otherwise noted. 2.0 1.5 1.0 0.5 0 1 2 4 3 OUTPUT CURRENT (A) 5 8026 G17 0 0 1 2 3 4 OUTPUT CURRENT (A) 5 8026 G18 8026fa 5 LTM8026 Typical Performance Characteristics TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable. 3.0 2.5 2.0 1.5 1.0 0.5 0 4.5 3.0 3.5 2.5 2.0 1.5 1.0 1 2 3 4 OUTPUT CURRENT (A) 0 5 0 1 2.0 1.5 0 5 2 3 4 OUTPUT CURRENT (A) 4.0 22VIN 24VIN 36VIN 3.0 2.5 2.0 1.5 3.0 2.5 2.0 1.5 1.0 0.5 0.5 0.5 1 2 3 4 OUTPUT CURRENT (A) 0 5 0 1 2 3 4 OUTPUT CURRENT (A) Input Current vs Input Voltage (Output Shorted) 1.6 600 1.4 400 300 200 2.0 12VIN 24VIN 32.5VIN 1.0 0.8 0.6 10 20 30 40 INPUT VOLTAGE (V) 8026 G25 0 5 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 2 3 4 OUTPUT CURRENT (A) 12VIN 24VIN 31VIN 1.6 1.2 0.4 100 1 Input Current vs Load Current –5VOUT 1.8 INPUT CURRENT (A) INPUT CURRENT (A) 500 0 8026 G24 Input Current vs Load Current –3.3VOUT 700 0 0 5 8026 G23 8026 G22 5 2 3 4 OUTPUT CURRENT (A) 28VIN 36VIN 3.5 1.0 0 1 Input Current vs Output Current 24VOUT 1.0 0 0 8026 G21 INPUT CURRENT (A) 2.5 1.5 Input Current vs Output Current 18VOUT 3.5 3.0 2.0 0.5 4.0 INPUT CURRENT (A) 3.5 INPUT CURRENT (A) 4.5 15VIN 24VIN 36VIN 4.0 2.5 8026 G20 Input Current vs Output Current 12VOUT 4.5 3.0 1.0 0.5 0 15VIN 24VIN 36VIN 4.0 8026 G19 INPUT CURRENT (mA) Input Current vs Output Current 8VOUT 8VIN 12VIN 24VIN 36VIN 3.5 INPUT CURRENT (A) INPUT CURRENT (A) 4.0 6VIN 12VIN 24VIN 36VIN Input Current vs Output Current 5VOUT INPUT CURRENT (A) 3.5 Input Current vs Output Current 3.3VOUT 0.2 0 1 2 4 3 OUTPUT CURRENT (A) 5 8026 G26 0 0 1 2 4 3 OUTPUT CURRENT (A) 5 8026 G27 8026fa 6 LTM8026 Typical Performance Characteristics TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable. Input Current vs Load Current –8VOUT 2.0 1.5 1.0 0.5 0 25 12VIN 24VIN 3.0 INPUT CURRENT (A) 2.5 INPUT CURRENT (A) 3.5 12VIN 24VIN 28VIN Minimum Required Input Running Voltage vs Negative Output Voltage 2.0 1.5 1.0 1 0 5 2 3 4 OUTPUT CURRENT (A) 15 10 5 0.5 0 IOUT = 4A IOUT = 3A IOUT = 2A IOUT = 1A 20 2.5 INPUT VOLTAGE (V) 3.0 Input Current vs Load Current –12VOUT 0 1 2 3 4 OUTPUT CURRENT (A) 8026 G28 0 5 0 –15 –5 –10 OUTPUT VOLTAGE (V) 8026 G30 8026 G29 Minimum Required Input Running Voltage vs Output Voltage, IOUT = 5A 6.4 30 Minimum Required Input Voltage vs Load 3.3VOUT and Below 7.2 Minimum Required Input Voltage vs Load 5VOUT 25 7.0 15 10 INPUT VOLTAGE (V) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 6.2 20 6.0 6.8 6.6 5.8 5 0 0 10 15 20 OUTPUT VOLTAGE (V) 5 25 5.6 30 0 1 3 2 LOAD CURRENT (A) 4 6.4 5 0 1 8026 G32 3 2 LOAD CURRENT (A) 4 5 8026 G33 8026 G31 Minimum Required Input Voltage vs Load 12VOUT 14.4 INPUT VOLTAGE (V) INPUT VOLTAGE (V) 21.5 14.2 9.8 9.6 9.4 9.2 9.0 Minimum Required Input Voltage vs Load 18VOUT 21.0 INPUT VOLTAGE (V) 10.0 Minimum Required Input Voltage vs Load 8VOUT 14.0 13.8 13.6 1 3 2 LOAD CURRENT (A) 4 5 8026 G34 13.2 20.0 19.5 13.4 0 20.5 0 1 2 3 LOAD CURRENT (A) 4 5 8026 G35 19.0 0 1 2 3 LOAD CURRENT (A) 4 5 8026 G36 8026fa 7 LTM8026 Typical Performance Characteristics TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable. Minimum Required Input Voltage vs Load 24VOUT Minimum Required Input Voltage vs Load –3.3VOUT 28.0 35 26.5 26.0 25.5 25 20 15 10 5 0 1 2 3 LOAD CURRENT (A) 0 5 4 0 1 2 3 5 3 4 2 3 60 36VIN 24VIN 12VIN 6VIN 50 15 10 0 5 5 4 Temperature Rise vs Load Current 2.5VOUT 20 40 30 20 10 1 0 LOAD CURRENT (A) 2 3 0 4 0 1 LOAD CURRENT (A) 2 3 5 4 LOAD CURRENT (A) 8026 G40 8026 G41 8026 G42 Temperature Rise vs Load Current 3.3VOUT Temperature Rise vs Load Current 5VOUT Temperature Rise vs Load Current 8VOUT 70 36VIN 24VIN 12VIN 6VIN 60 TEMPERATURE RISE (°C) 50 40 30 20 10 90 36VIN 24VIN 12VIN 7VIN 50 40 30 20 10 0 1 2 3 4 5 LOAD CURRENT (A) 0 70 60 50 40 30 20 10 0 1 2 3 4 5 LOAD CURRENT (A) 8026 G43 36VIN 24VIN 12VIN 80 TEMPERATURE RISE (°C) 60 TEMPERATURE RISE (°C) 1 8026 G39 5 2 0 LOAD CURRENT (A) TEMPERATURE RISE (°C) 10 0 0 5 4 TO START RUN CONTROLLED TO RUN 25 INPUT VOLTAGE (V) INPUT VOLTAGE (V) 30 15 1 10 8026 G38 TO START RUN CONTROLLED TO RUN 0 15 Minimum Required Input Voltage vs Load –12VOUT 20 0 20 LOAD CURRENT (A) Minimum Required Input Voltage vs Load –8VOUT 25 25 5 8026 G37 30 TO START RUN CONTROLLED TO RUN 30 INPUT VOLTAGE (V) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 27.0 35 TO START RUN CONTROLLED TO RUN 30 27.5 Minimum Required Input Voltage vs Load –5VOUT 8026 G44 0 0 1 3 2 LOAD CURRENT (A) 4 5 8026 G45 8026fa 8 LTM8026 Typical Performance Characteristics TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable. Temperature Rise vs Load Current 12VOUT 80 60 40 100 36VIN 24VIN 100 TEMPERATURE RISE (°C) 100 TEMPERATURE RISE (°C) 120 36VIN 24VIN 15VIN 60 40 20 0 0 36VIN 28VIN 90 80 20 Temperature Rise vs Load Current 24VOUT TEMPERATURE RISE (°C) 120 Temperature Rise vs Load Current 18VOUT 80 70 60 50 40 30 20 10 0 1 2 3 4 5 1 0 0 5 4 0 1 3 2 LOAD CURRENT (A) 4 5 8026 G46 8026 G47 8026 G48 Temperature Rise vs Load Current –3.3VOUT Temperature Rise vs Load Current –5VOUT Temperature Rise vs Load Current –8VOUT 80 12VIN 32.5VIN 24VIN 70 TEMPERATURE RISE (°C) 60 50 40 30 20 10 90 12VIN 31VIN 24VIN 60 50 40 30 20 10 1 2 3 4 0 5 1 0 2 3 LOAD CURRENT (A) 4 5 8026 G49 40 30 20 0 0 1 3 2 LOAD CURRENT (A) 4 5 8026 G51 Switching Frequency vs RT Value 500 24VIN 12VIN 100 50 8026 G50 Temperature Rise vs Load Current –12VOUT 120 70 60 10 LOAD CURRENT (A) 450 400 350 80 RT VALUE (kΩ) TEMPERATURE RISE (°C) 0 12VIN 28VIN 24VIN 80 TEMPERATURE RISE (°C) 70 TEMPERATURE RISE (°C) 3 LOAD CURRENT (A) LOAD CURRENT (A) 0 2 60 40 300 250 200 150 100 20 50 0 0 1 2 3 4 LOAD CURRENT (A) 8026 G52 0 0 0.2 0.6 0.8 0.4 SWITCHING FREQUENCY (MHz) 1.0 8026 G53 8026fa 9 LTM8026 Typical Performance Characteristics TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable. CTL_T Voltage vs Load Current, CTL_I = 2V 2.5 2.5 2.0 2.0 CTL_T VOLTAGE (V) CTL_I VOLTAGE (V) CTL_I Voltage vs Load Current, CTL_T = 2V 1.5 1.0 1.0 0.5 0.5 0 1.5 0 1 3 4 2 LOAD CURRENT (A) 5 6 8026 G54 0 0 1 3 4 2 LOAD CURRENT (A) 5 6 8026 G55 Pin Functions VOUT (Bank 1): Power Output Pins. Apply the output filter capacitor and the output load between these pins and GND pins. GND (Bank 2): Tie these GND pins to a local ground plane below the LTM8026 and the circuit components. In most applications, the bulk of the heat flow out of the LTM8026 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. Return the feedback divider (RADJ) to this net. VIN (Bank 3): The VIN pins supply current to the LTM8026’s internal regulator and to the internal power switches. These pins must be locally bypassed with an external, low ESR capacitor; see Table 1 for recommended values. CTL_T (Pin D8): Connect a resistor/NTC thermistor network to the CTL_T pin to reduce the maximum regulated output current of the LTM8026 in response to temperature. The maximum control voltage is 1.5V. If this function is not used, tie this pin to VREF . CTL_I (Pin E8): The CTL_I pin reduces the maximum regulated output current of the LTM8026. The maximum control voltage is 1.5V. If this function is not used, tie this pin to VREF . VREF (Pin F8): Buffered 2V Reference Capable of 0.5mA Drive. RT (Pin G8): The RT pin is used to program the switching frequency of the LTM8026 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. When using the SYNC function, apply a resistor value equivalent to 20% lower than the SYNC pulse frequency. Do not leave this pin open. COMP (Pin H8): Compensation Pin. This pin is generally not used. The LTM8026 is internally compensated, but some rare situations may arise that require a modification to the control loop. This pin connects directly to the PWM comparator of the LTM8026. In most cases, no adjustment is necessary. If this function is not used, leave this pin open. 8026fa 10 LTM8026 Pin Functions SS (Pin J8): The Soft-Start Pin. Place an external capacitor to ground to limit the regulated current during start-up conditions. The soft-start pin has an 11µA charging current. ADJ (Pin K8): The LTM8026 regulates its ADJ pin to 1.19V. Connect the adjust resistor from this pin to ground. The value of RADJ is given by the equation: RADJ = 11.9 VOUT – 1.19 where RADJ is in kΩ. RUN (Pin L6): The RUN pin acts as an enable pin and turns on the internal circuitry. The RUN pin is internally clamped, so it may be pulled up to a voltage source that is higher than the absolute maximum voltage of 6V through a resistor, provided the pin current does not exceed 100µA. Do not leave this pin open. It may also be used to implement a precision UVLO. See the Applications Information section for details. SYNC (Pin L7): Frequency Synchronization Pin. This pin allows the switching frequency to be synchronized to an external clock. The RT resistor should be chosen to operate the internal clock at 20% lower than the SYNC pulse frequency. This pin should be grounded when not in use. Do not leave this pin floating. When laying out the board, avoid noise coupling to or from the SYNC trace. See the Synchronization section in Applications Information. Block Diagram 2.2µH VIN 0.2µF RSENSE VOUT 10k 2.2µF RUN SS SYNC VREF CURRENT MODE CONTROLLER VIN CTL_I INTERNAL REGULATOR CTL_T COMP GND RT ADJ 8026 BD 8026fa 11 LTM8026 Operation The LTM8026 is a standalone nonisolated step-down switching DC/DC power supply that can deliver up to 5A of output current. This µModule regulator provides a precisely regulated output voltage programmable via one external resistor from 1.2V to 24V. The input voltage range is 6V to 36V. Given that the LTM8026 is a step-down converter, make sure that the input voltage is high enough to support the desired output voltage and load current. The RUN pin functions as a precision shutdown pin. When the voltage at the RUN pin is lower than 1.55V, switching is terminated. Below the turn-on threshold, the RUN pin sinks 5.5µA. This current can be used with a resistor between RUN and VIN to the set a hysteresis. During startup, the SS pin is held low until the part is enabled, after which the capacitor at the soft-start pin is charged with an 11µA current source. As shown in the Block Diagram, the LTM8026 contains a current mode controller, power switches, power inductor, and a modest amount of input and output capacitance. The LTM8026 is equipped with a thermal shutdown to protect the device during momentary overload conditions. It is set above the 125°C absolute maximum internal temperature rating to avoid interfering with normal specified operation, so internal device temperatures will exceed the absolute maximum rating when the overtemperature protection is active. So, continuous or repeated activation of the thermal shutdown may impair device reliability. During thermal shutdown, all switching is terminated and the SS pin is driven low. The LTM8026 utilizes fixed frequency, average current mode control to accurately regulate the inductor current, independently from the output voltage. This is an ideal solution for applications requiring a regulated current source. The control loop will regulate the current in the internal inductor. Once the output has reached the regulation voltage determined by the resistor from the ADJ pin to ground, the inductor current will be reduced by the voltage regulation loop. The current control loop has two reference inputs, determined by the voltage at the analog control pins, CTL_I and CTL_T . CTL_I is typically used to set the maximum allowable current output of the LTM8026, while CTL_T is typically used with a NTC thermistor to reduce the output current in response to temperature. The lower of the two analog voltages on CTL_I and CTL_T determines the regulated output current. The analog control range of both the CTL_I and CTL_T pin is from 0V to 1.5V. The switching frequency is determined by a resistor at the RT pin. The LTM8026 may also be synchronized to an external clock through the use of the SYNC pin. 8026fa 12 LTM8026 Applications Information For most applications, the design process is straight forward, 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, RADJ and RT values. 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 Table 1. Recommended Component Values and Configuration. (TA = 25°C. See Typical Performance Characteristics for Load Conditions) VIN 6V to 36V VOUT 1.2 6V to 36V 1.5 6V to 36V 1.8 6V to 36V 6V to 36V 7V to 36V 10V to 36V 15V to 36V 22V to 36V 28V to 36V 9V to 15V 2.5 3.3 5 8 12 18 24 1.2 9V to 15V 1.5 9V to 15V 1.8 9V to 15V 9V to 15V 9V to 15V 10V to 15V 18V to 36V 2.5 3.3 5 8 1.2 18V to 36V 1.5 18V to 36V 1.8 CIN COUT CERAMIC COUT ELECTROLYTIC 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9m_, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9m_, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9m_, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 10µF, 50V, 1210 100µF, 6.3V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 100µF, 10V, 1210 120µF, 16V, 27m_, OS-CON, 16SVPC120M 10µF, 50V, 1210 47µF, 16V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 22µF, 25V, 1210 47µF, 20V, 45mΩ, OS-CON, 20SVPS47M 4.7µF, 50V, 1210 10µF, 50V, 1206 47µF, 35V, 30mΩ, OS-CON, 35SVPC47M 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 10µF, 50V, 1210 100µF, 6.3V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 100µF, 10V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 10µF, 50V, 1210 100µF, 6.3V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 100µF, 10V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 47µF, 16V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 18V to 36V 2.5 18V to 36V 3.3 18V to 36V 5 18V to 36V 8 18V to 36V 12 2.7V to –3.3 32.5V* 2V to 31V* –5 10µF, 50V, 1210 100µF, 6.3V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 10µF, 50V, 1210 100µF, 10V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 2V to 28V* –8 3V to 24V* –12 10µF, 50V, 1210 47µF, 16V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M *Running voltage. Requires at least 6VIN to start. Note: An input bulk capacitor is required. RADJ fOPTIMAL RT(OPTIMAL) fMAX RT(MIN) Open 200kHz 210k 250kHz 169k 38.3k 300kHz 140k 350kHz 118k 19.6k 350kHz 118k 400kHz 102k 9.09k 5.62k 3.09k 1.74k 1.10k 604 523 Open 450kHz 550kHz 600kHz 625kHz 650kHz 675kHz 700kHz 200kHz 90.9k 75.0k 68.1k 64.9k 61.9k 59.0k 57.6k 210k 525kHz 625kHz 700kHz 750kHz 800kHz 900kHz 1MHz 525kHz 78.7k 64.9k 57.6k 53.6k 49.9k 44.2k 39.2k 78.7k 38.3k 300kHz 140k 650kHz 61.9k 19.6k 350kHz 118k 800kHz 49.9k 9.09k 5.62k 3.09k 1.74k Open 450kHz 550kHz 600kHz 625kHz 200kHz 90.9k 75.0k 68.1k 64.9k 210k 1MHz 1MHz 1MHz 1MHz 250kHz 39.2k 39.2k 39.2k 39.2k 169k 38.3k 300kHz 140k 350kHz 118k 19.6k 350kHz 118k 400kHz 102k 9.09k 5.62k 3.09k 1.74k 1.10k 5.62k 450kHz 550kHz 600kHz 625kHz 650kHz 550kHz 90.9k 75.0k 68.1k 64.9k 61.9k 75.0k 525kHz 625kHz 700kHz 750kHz 800kHz 625kHz 78.7k 64.9k 57.6k 53.6k 49.9k 64.9k 3.09k 1.74k 1.10k 600kHz 625kHz 650kHz 68.1k 64.9k 61.9k 700kHz 750kHz 800kHz 57.6k 53.6k 49.9k 8026fa 13 LTM8026 Applications Information graphs in the Typical Performance Characteristics section for guidance. The maximum frequency (and attendant RT value) at which the LTM8026 should be allowed to switch is given in Table 1 in the fMAX column, while the recommended frequency (and RT value) for optimal efficiency over the given input condition is given in the fOPTIMAL column. There are additional conditions that must be satisfied if the synchronization function is used. Please refer to the Switching Frequency Synchronization section for details. Capacitor Selection Considerations 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 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, 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. Many of the output capacitances given in Table 1 specify an electrolytic capacitor. Ceramic capacitors may also be used in the application, but it may be necessary to use more of them. Many high value ceramic capacitors have a large voltage coefficient, so the actual capacitance of the component at the desired operating voltage may be only a fraction of the specified value. Also, the very low ESR of ceramic capacitors may necessitate additional capacitors for acceptable stability margin. A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LTM8026. A ceramic input capacitor combined with trace or cable inductance forms a high Q (under damped) tank circuit. If the LTM8026 circuit is plugged into a live supply, the 14 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. Programming Switching Frequency The LTM8026 has an operational switching frequency range between 100kHz and 1MHz. This frequency is programmed with an external resistor from the RT pin to ground. Do not leave this pin open under any circumstance. See Table 2 for resistor values and the corresponding switching frequencies. Table 2. RT Resistor Values and Their Resultant Switching Frequencies SWITCHING FREQUENCY (MHz) 1 0.750 0.5 0.3 0.2 0.1 RT (kΩ) 39.2 53.6 82.5 140 210 453 In addition, the Typical Performance Characteristics section contains a graph that shows the switching frequency versus RT value. To improve efficiency at light load, the part will enter discontinuous mode. Switching 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 LTM8026 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 LTM8026 in some fault conditions. 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. Switching Frequency Synchronization The nominal switching frequency of the LTM8026 is determined by the resistor from the RT pin to GND and 8026fa LTM8026 Applications Information may be set from 100kHz to 1MHz. The internal oscillator may also be synchronized to an external clock through the SYNC pin. The external clock applied to the SYNC pin must have a logic low below 0.6V and a logic high greater than 1.2V. The input frequency must be 20% higher than the frequency determined by the resistor at the RT pin. In general, the duty cycle of the input signal should be greater than 10% and less than 90%. Input signals outside of these specified parameters may cause erratic switching behavior and subharmonic oscillations. The SYNC pin must be tied to GND if the synchronization to an external clock is not required. When SYNC is grounded, the switching frequency is determined by the resistor at the RT pin. At light loads, the LTM8026 will enter discontinuous operation to improve efficiency even while a valid clock signal is applied to the SYNC pin. 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 11µA current source to produce a ramped output voltage. Load Current Derating Using the CTL_T Pin In high current applications, derating the maximum current based on operating temperature may prevent damage to the load. In addition, many applications have thermal limitations that will require the regulated current to be reduced based on the load and/or board temperature. To achieve this, the LTM8026 uses the CTL_T pin to reduce the effective regulated current in the load. While CTL_I programs the regulated current in the load, CTL_T can be configured to reduce this regulated current based on the analog voltage at the CTL_T pin. The load/board temperature derating is programmed using a resistor divider with a temperature dependant resistance (Figure 2). When the board/load temperature rises, the CTL_T voltage will decrease. To reduce the regulated current, the CTL_T voltage must be lower than the voltage at the CTL_I pin. CTL_T may be higher than CTL_I, but then it will have no effect. Voltage Regulation and Output Overvoltage Protection The LTM8026 uses the ADJ pin to regulate the output voltage and to provide a high speed overvoltage lockout to avoid high voltage conditions. If the output voltage exceeds 125% of the regulated voltage level (1.5V at the ADJ pin), the LTM8026 terminates switching and shuts Maximum Output Current Adjust To adjust the regulated load current, an analog voltage is applied to the CTL_I pin or CTL_T pins. Varying the voltage between 0V and 1.5V adjusts the maximum current between the minimum and the maximum current, 5.6A typical. Graphs of the output current vs CTL_I and CTL_T voltages are given in the Typical Performance Characteristics section. The LTM8026 provides a 2V reference voltage for conveniently applying resistive dividers to set the current limit. The current limit can be set as shown in Figure 1 with the following equation: IMAX 7.467 • R2 = Amps R1+R2 VREF 2V LTM8026 R1 CTL_I OR CTL_T R2 8026 F01 Figure 1. Setting the Output Current Limit, IMAX RV RV VREF R2 LTM8026 RNTC RNTC RX RNTC RNTC RX CTL_T R1 (OPTION A TO D) 8026 F02 A B C D Figure 2. Load Current Derating vs Temperature Using NTC Resistor 8026fa 15 LTM8026 Applications Information down switching for 13µs. The regulated output voltage must be greater than 1.21V and is set by the equation: RADJ = 11.9 kΩ VOUT – 1.19 1.55 • R2 UVLO – 1.55 V – 1.084 • UVLO R2 = ENA 5.5µA R1= where RADJ is shown in Figure 3. VOUT divider resistors for programming the falling UVLO voltage and rising enable voltage (VENA) as configured in Figure 4. VOUT LTM8026 ADJ RADJ 8026 F03 The RUN pin has an absolute maximum voltage of 6V. To accommodate the largest range of applications, there is an internal Zener diode that clamps this pin, so that it can be pulled up to a voltage higher than 6V through a resistor that limits the current to less than 100µA. For applications where the supply range is greater than 4:1, size R2 greater than 375k. Figure 3. Voltage Regulation and Overvoltage Protection Feedback Connections VIN Thermal Shutdown If the part is too hot, the LTM8026 engages its thermal shutdown, terminates switching and discharges the softstart capacitor. When the part has cooled, the part automatically restarts. This thermal shutdown is set to engage at temperatures above the 125°C absolute maximum internal operating rating to ensure that it does not interfere with functionality in the specified operating range. This means that internal temperatures will exceed the 125°C absolute maximum rating when the overtemperature protection is active, possibly impairing the device’s reliability. LTM8026 R2 RUN R1 8026 F04 Figure 4. UVLO Configuration Load Sharing Two or more LTM8026s may be paralleled to produce higher currents. To do this, simply tie VOUT, SS, RUN and ADJ together. The value of the ADJ resistor is given by the equation: Shutdown and UVLO The LTM8026 has an internal UVLO that terminates switching, resets all logic, and discharges the soft-start capacitor when the input voltage is below 6V. The LTM8026 also has a precision RUN function that enables switching when the voltage at the RUN pin rises to 1.68V and shuts down the LTM8026 when the RUN pin voltage falls to 1.55V. There is also an internal current source that provides 5.5μA of pull-down current to program additional UVLO hysteresis. For RUN rising, the current source is sinking 5.5µA until RUN = 1.68V, after which it turns off. For RUN falling, the current source is off until the RUN = 1.55V, after which it sinks 5.5µA. The following equations determine the voltage VIN RADJ = 11.9 kΩ n ( VOUT – 1.19) where n is the number of LTM8026s in parallel. Given the LTM8026’s accurate current limit and CVCC operation, each paralleled unit will contribute a portion of the output current, up to the amount determined by the CTL_I and CTL_T pins. An example of this is given in the Typical Applications section. Two or more LTM8026s can share load current equally by using a simple op amp circuit to simultaneously modulate the CTL_I pins. Tie SS, RUN, and VOUT and CTL_I of all of the paralleled LTM8026s together. An example of two 8026fa 16 LTM8026 The LTM8026’s CVCC operation provides the ability to power share the load among several input voltage sources. An example of this is shown in the Typical Applications section; please refer to the schematic while reading this discussion. Suppose the application powers 2.5V at 8A and the system under consideration has regulated 24V and 12V input rails available. The power budget for the power rails says that each can allocate only 750mA to produce 2.5V. From the Input Current vs Output Current graph in the Typical Performance Characteristics section for 2.5VOUT, 750mA from the 24V rail can support more than 5A output current, so apply a 66.5k/140k from VREF to the CTL_I pin of the LTM8026 powered from 24VIN to set the output current to 5A. These resistor values were derived as follows: 1.The typical output current limit is 5.6A for CTL_I = 1.5V and above. 2.To get 5A, make the voltage on CTL_I = 1.5V • 5A/5.6A = 1.34V. 3.The VREF node is a regulated 2V, so applying the 66.5k/140k network yields 2V • 140k/(66.5k + 140k) = 1.35V The LTM8026 powered from 12VIN needs to supply the rest of the load current, or 3A. Again referring to the Input Current vs Output Current graph in the Typical Performance Characteristics section for 2.5VOUT, 750mA will support more than 3A when operated from 12VIN. Using a method similar to the above, apply a resistor network of 132k/78.7k to the CTL_I pin: 1.To get 2.5A, make the voltage on CTL_I = 1.5V • 3A/5.6A = 0.8V • • • • GND • • • • • • • • • • • • • • • • • • SYNC RUN • • • • • • • • • • • • • VIN VOUT GND SS ADJ • • • COUT VREF RT CTL_I CTL_T LTM8026s equally sharing output current is shown in the Typical Applications section. The modulation of the CTL_I inputs is performed at a high bandwidth, so use an op amp with a gain bandwidth product greater than 1MHz. The example circuit in the Typical Applications section uses the LTC6255, which has a minimum gain bandwidth product of 2MHz. COMP Applications Information VOUT CIN GND • THERMAL AND INTERCONNECT VIAS VIN 8026 F05 Figure 5. Layout Showing Suggested External Components, GND Plane and Thermal Vias. As seen in the graph accompanying the schematic in the Typical Applications section, the input currents to each LTM8026 stays below 750mA for all loads below 8A. PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8026. The LTM8026 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 5 for a 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 LTM8026. 2.Applying a 132k/88.7k network to VREF and CTL_I yields 2V • 88.7k/(88.7k + 132k) = 0.8V 8026fa 17 LTM8026 Applications Information 3. Place the COUT capacitor as close as possible to the VOUT and GND connection of the LTM8026. 4. Place the CIN and COUT capacitors such that their ground current flow directly adjacent or underneath the LTM8026. 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 LTM8026. 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 5. The LTM8026 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. Hot Plugging Safely The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of LTM8026. However, these capacitors can cause problems if the LTM8026 is plugged into a live input supply (see 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 LTM8026 can ring to more than twice the nominal input voltage, possibly exceeding the LTM8026’s rating and damaging the part. If the input supply is poorly controlled or the user will be plugging the LTM8026 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 to add an electrolytic bulk capacitor to the VIN net. This capacitor’s relatively high equivalent series resistance damps the circuit and eliminates the voltage overshoot. The extra capacitor improves low frequency ripple filtering and can slightly improve the efficiency of the circuit, though it is physically large. Thermal Considerations The LTM8026 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 temperature rise curves given in the Typical Performance Characteristics section can be used as a guide. These curves were generated by the LTM8026 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 finite element analysis (FEA) 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 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. 8026fa 18 LTM8026 Applications Information 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 really 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 2-sided, 2-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 6. The blue resistances are contained within the µModule device, and the green are outside. The die temperature of the LTM8026 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 LTM8026. The bulk of the heat flow out of the LTM8026 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. 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 8026 F06 µMODULE DEVICE Figure 6 8026fa 19 LTM8026 Typical Applications 36VIN, 3.3VOUT Step-Down CVCC Converter VIN 6V TO 36V 10µF 510k VIN VOUT 3.3V 5A LTM8026 VOUT RUN SS + VREF SYNC CTL_I COMP CTL_T GND ADJ RT 330µF 100µF 5.62k 75.0k 8026 TA02 36VIN, 5.6A Two 2.5V Series Supercapacitor Charger VIN 7V TO 36V 10µF 510k VIN LTM8026 VOUT VOUT 5V RUN SS 2.5V 2.2F VREF SYNC CTL_I COMP CTL_T GND ADJ RT 47µF 2.5V 2.2F 3.09k 68.1k 8026 TA03 36VIN, 12VOUT Step-Down CVCC Converter VIN 15V TO 36V 10µF 510k VIN VOUT 12V 3.5A LTM8026 VOUT RUN SS SYNC COMP RT 61.9k VREF + CTL_I CTL_T GND ADJ 120µF 47µF 1.1k 8026 TA04 8026fa 20 LTM8026 Typical Applications 31VIN, –5VOUT Negative CVCC Converter VIN 7V TO 31V 10µF VIN LTM8026 VOUT RUN SS 5V 0 2N3906 20k 20k 20k VREF SYNC CTL_I 120µF + 100µF OPTIONAL CTL_T COMP RT GND ADJ 3.09k 68.1k OPTIONAL: SEE DESIGN NOTE 1021 8026 TA05 VOUT –5V 5A Two LTM8026s Operating in Parallel to Produce 2.5VOUT at 10A VIN 6V TO 36V 10µF 324k VIN LTM8026 VOUT VOUT 2.5V 10A RUN SS VREF SYNC CTL_I COMP CTL_T GND ADJ RT 100µF 4.53k 75k VIN LTM8026 VOUT RUN SS VREF SYNC CTL_I COMP CTL_T GND ADJ RT 100µF + 330µF 75k 8026 TA06 8026fa 21 LTM8026 Typical Applications Two LTM8026s Operating in Parallel to Produce 2.5VOUT at 10A, Equally Sharing Current VIN 6V TO 36V 10µF VIN 324k LTM8026 VOUT VOUT 2.5V 10A RUN SS VREF SYNC CTL_T COMP CTL_I GND ADJ RT 100µF 4.02k 75k 470pF 680k LTM8026 VIN VOUT CTL_I GND ADJ RT + VOUT 150k 100k 100k 100k LTC6255 + CTL_T COMP 330µF – 0.1µF 100µF VREF SYNC VREF 0.47µF RUN SS VOUT 75k 8026 TA09 Two LTM8026s Running from 12V and 24V. At Max Load, Each LTM8026 Draws Less Than 750mA from Their Respective Input Sources <750mA 10µF 324k VIN LTM8026 VOUT RUN SS CTL_I COMP CTL_T GND ADJ 10µF VIN 100µF 700 66.5k 600 140k LTM8026 VOUT RUN SS VREF SYNC CTL_I COMP CTL_T GND ADJ RT 132k 20 500 15 400 300 10 200 5 100 100µF + 25 24V INPUT CURRENT 12V INPUT CURRENT TOTAL INPUT POWER 330µF 0 0 4 6 2 OUTPUT CURRENT (A) 8 TOTAL INPUT POWER (W) 4.53k 90.9k <750mA Input Current vs Output Current VREF SYNC RT VIN1 REGULATED 12V VOUT 2.5V 8A INPUT CURRENT (mA) VIN1 REGULATED 24V 0 8026 TA07b 90.9k 88.7k 8026 TA07 8026fa 22 LTM8026 Package Description Table 3. Pin Assignment Table (Arranged by Pin Number) PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME A1 VOUT B1 VOUT C1 VOUT D1 VOUT E1 GND F1 GND A2 VOUT B2 VOUT C2 VOUT D2 VOUT E2 GND F2 GND A3 VOUT B3 VOUT C3 VOUT D3 VOUT E3 GND F3 GND A4 VOUT B4 VOUT C4 VOUT D4 VOUT E4 GND F4 GND A5 GND B5 GND C5 GND D5 GND E5 GND F5 GND A6 GND B6 GND C6 GND D6 GND E6 GND F6 GND A7 GND B7 GND C7 GND D7 GND E7 GND F7 GND A8 GND B8 GND C8 GND D8 CTL_T E8 CTL_I F8 VREF PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME G1 GND J1 VIN K1 VIN L1 VIN G2 GND J2 VIN K2 VIN L2 VIN G3 GND J3 VIN K3 VIN L3 VIN G4 GND G5 GND H5 GND J5 GND K5 GND L5 GND G6 GND H6 GND J6 GND K6 GND L6 RUN G7 GND H7 GND J7 GND K7 GND L7 SYNC G8 RT H8 COMP J8 SS K8 ADJ L8 GND Package Photo 8026fa 23 aaa Z 0.630 ±0.025 Ø 81x 3.175 SUGGESTED PCB LAYOUT TOP VIEW 1.905 PACKAGE TOP VIEW E 0.000 4 0.635 Y X D 6.350 5.080 0.000 5.080 6.350 aaa Z 2.45 – 2.55 SYMBOL A b D E e F G aaa bbb eee 0.15 0.10 0.05 MAX 2.92 0.66 NOTES DETAIL B TOTAL NUMBER OF LGA PADS: 81 NOM 2.82 0.63 15.0 11.25 1.27 12.70 8.89 DIMENSIONS 0.27 – 0.37 SUBSTRATE eee S X Y MIN 2.72 0.60 DETAIL A DIA (0.630) 81x DETAIL B MOLD CAP A (Reference LTC DWG # 05-08-1868 Rev Ø) // bbb Z PAD “A1” CORNER 0.635 Z 24 1.905 LGA Package 81-Lead (15mm × 11.25mm × 2.82mm) e b 7 5 G 4 e 3 PACKAGE BOTTOM VIEW 6 2 1 L K J H G F E D C B A 3 SEE NOTES PAD 1 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 TRAY PIN 1 BEVEL COMPONENT PIN “A1” LGA 81 0310 REV Ø PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX µModule 6. THE TOTAL NUMBER OF PADS: 81 5. PRIMARY DATUM -Z- IS SEATING PLANE LAND DESIGNATION PER JESD MO-222, SPP-010 3 2. ALL DIMENSIONS ARE IN MILLIMETERS NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 F b 8 DETAIL A LTM8026 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. 8026fa 4.445 3.175 4.445 LTM8026 Revision History REV DATE DESCRIPTION A 8/12 Added MP-Grade. PAGE NUMBER 2-3 8026fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 25 LTM8026 Typical Application 36VIN, 3.3VOUT Step-Down Converter with 4.75A Accurate Current Limit VIN 6V TO 36V 10µF VIN 510k LTM8026 VOUT VOUT 3.3V 4.75A RUN SS VREF SYNC CTL_I COMP CTL_T GND ADJ RT 75k 100µF + 330µF 71.5k 5.62k 127k 8026 TA08 Related Parts PART NUMBER DESCRIPTION COMMENTS LTM8062 32VIN, 2A µModule Battery Charger with Maximum Peak Power Tracking (MPPT) Adjustable VBATT up to 14.4V, C/10 or Timer Termination, 9mm × 15mm × 4.32mm LGA Package LTM8027 60VIN, 4A DC/DC Step-Down µModule Regulator 4.5V ≤ VIN ≤ 60V, 2.5V ≤ VOUT ≤ 24V, 15mm × 15mm × 4.32mm LGA Package LTM8052 36VIN, ±5A µModule Regulator with Adjustable Accurate Current Limit 6V ≤ VIN ≤ 36V, 1.2V ≤ VOUT ≤ 24V, –5V ≤ IOUT ≤ 5A, Synchronizable, Pin Compatible with LTM8026, 11.25mm × 15mm × 2.82mm LGA Package LTM4618 26VIN, 6A Step-Down µModule Regulator 4.5V ≤ VIN ≤ 26.5V, 0.8V ≤ VOUT ≤ 5V, Synchronizable, VOUT Tracking, 9mm × 15mm × 4.3mm LGA Package LTM4612 5A EN55022 Class B DC/DC Step-Down µModule Regulator 5V ≤ VIN ≤ 36V, 3.3V ≤ VOUT ≤ 15V, PLL Input, VOUT Tracking and Margining, 15mm × 15mm × 2.8mm LGA Package 8026fa 26 Linear Technology Corporation LT 0812 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2012