LTM8068 2.8VIN to 40VIN Isolated Module DC/DC Converter with LDO Post Regulator FEATURES DESCRIPTION 2kVAC Isolated Module Converter UL60950 Recognized File E464570 nn Wide Input Voltage Range: 2.8V to 40V nn V OUT1 Output: nn Up to 450mA (V = 24V V IN , OUT1 = 5V) nn 2.5V to 18V Output Range nn V OUT2 Low Noise Linear Post Regulator: nn Up to 300mA nn 1.2V to 18V Output Range nn Current Mode Control nn User Configurable Undervoltage Lockout nn Low Profile (9mm x 11.25mm x 4.92mm) BGA Package The LTM(R)8068 is a 2kVAC isolated flyback Module(R) (power module) DC/DC converter with LDO post regulator. Included in the package are the switching controller, power switches, transformer, LDO, and all support components. Operating over an input voltage range of 2.8V to 40V, the LTM8068 supports an output voltage range of 2.5V to 18V, set by a single resistor. There is also a linear post regulator whose output voltage is adjustable from 1.2V to 18V as set by a single resistor. Only output and input capacitors are needed to finish the design. nn nn The LTM8068 is packaged in a thermally enhanced, compact (9mm x 11.25mm x 4.92mm) overmolded ball grid array (BGA) package suitable for automated assembly by standard surface mount equipment. The LTM8068 is available with SnPb or RoHS compliant terminal finish. APPLICATIONS L, LT, LTC, LTM, Linear Technology, the Linear logo and Module are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. Industrial Sensors nn Industrial Switches nn Ground Loop Mitigation nn TYPICAL APPLICATION 2kVAC Isolated Low Noise Module Regulator Total Output Current vs VIN 350 RUN 2.2F * (5.6V) 22F VOUT2 * LOW NOISE LDO FB2 VOUTN 162k VOUT2 5V 300mA MAX 10F FB1 7.32k GND LTM8068 LOAD CURRENT (mA) VOUT1 VIN VIN 2.8V TO 38V 250 150 8068 TA01a PIN BYP IS NOT USED IN THIS SCHEMATIC 50 0 9 18 VIN (V) 27 36 8068 TA01 8068fb For more information www.linear.com/LTM8068 1 LTM8068 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW VIN, RUN ...................................................................42V VOUT1 Relative to VOUTN.............................................25V VIN + VOUT1 (Note 2)..................................................45V VOUT2 Relative to VOUTN...........................................+20V FB2 Relative to VOUTN................................................+7V GND to VOUTN Isolation (Note 3)............................2kVAC Maximum Internal Temperature (Note 4)............... 125C Maximum Peak Body Reflow Temperature............ 245C Storage Temperature.............................. -55C to 125C A FB2 B C BANK 3 BYP VOUT2 BANK 2 VOUTN BANK 1 VOUT1 D E BANK 5 VIN F G BANK 4 GND RUN FB1 H 1 2 3 4 5 6 7 BGA PACKAGE 38-LEAD (11.25mm x 9mm x 4.92mm) TJMAX = 125C, JA = 18.2C/W, JCbottom = 4.8C/W, JCtop = 18.1C/W, JB = 4.8C/W WEIGHT = 1.1g, VALUES DETERMINED PER JEDEC 51-9, 51-12 ORDER INFORMATION http://www.linear.com/product/LTM8068#orderinfo PART MARKING* PART NUMBER PAD OR BALL FINISH LTM8068EY#PBF SAC305 (RoHS) DEVICE FINISH CODE PACKAGE TYPE MSL RATING LTM8068Y e1 BGA 3 TEMPERATURE RANGE (Note 4) -40C to 125C LTM8068IY#PBF SAC305 (RoHS) LTM8068Y e1 BGA 3 -40C to 125C LTM8068IY SnPb (63/37) LTM8068Y e0 BGA 3 -40C to 125C Consult Marketing for parts specified with wider operating temperature ranges. *Device temperature grade is indicated by a label on the shipping container. Pad or ball finish code is per IPC/JEDEC J-STD-609. * Recommended LGA and BGA PCB Assembly and Manufacturing Procedures: www.linear.com/umodule/pcbassembly * Terminal Finish Part Marking: www.linear.com/leadfree * LGA and BGA Package and Tray Drawings: www.linear.com/packaging 2 8068fb For more information www.linear.com/LTM8068 LTM8068 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25C, RUN = 2V (Note 4). PARAMETER CONDITIONS Minimum Input DC Voltage RUN = 2V l VOUT1 DC Voltage RFB1 = 15.4k RFB1 = 8.25k RFB1 = 2.37k l VIN Quiescent Current VRUN = 0V Not Switching MIN 4.75 TYP 2.5 5 18 7 MAX UNITS 2.8 V 5.25 V V V 3 A mA VOUT1 Line Regulation 3V VIN 40V, IOUT = 0.1A, RUN = 2V 1 % VOUT1 Load Regulation 0.05A IOUT 0.3A, RUN = 2V 1 % VOUT1 Ripple (RMS) IOUT = 0.1A, 1MHz BW 30 mV Isolation Voltage (Note 3) 2 kV Input Short-Circuit Current VOUT1 Shorted 80 mA RUN Pin Input Threshold RUN Pin Falling RUN Pin Current VRUN = 1V VRUN = 1.3V 2.5 LDO (VOUT2) Minimum Input DC Voltage (Note 5) 1.5 VOUT2 Voltage Range VOUT1 = 16V, RFB2 Open, No Load (Note 5) VOUT1 = 16V, RFB2 = 41.2k, No Load (Note 5) 1.22 17.7 FB2 Pin Voltage VOUT1 = 2V, IOUT2 = 1mA (Note 5) VOUT1 = 2V, IOUT2 = 1mA (Note 5) 1.18 l 1.19 1.214 1.22 1.25 V 0.1 A A 2.3 V V V 1.25 V V VOUT2 Line Regulation 2V < VOUT1 < 16V, IOUT2 = 1mA (Note 5) 1 5 mV VOUT2 Load Regulation VOUT1 = 5V, 10mA IOUT2 300mA (Note 5) 2 10 mV LDO Dropout Voltage IOUT2 = 10mA (Note 5) IOUT2 = 100mA (Note 5) IOUT2 = 300mA (Note 5) VOUT2 Ripple (RMS) CBYP = 0.01F, IOUT2 = 300mA, BW = 100Hz to 100kHz (Note 5) 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: VIN + VOUT1 is defined as the sum of: (VIN - GND) + (VOUT1 - VOUTN) Note 3: The LTM8068 isolation test voltage of either 2kVAC or its equivalent of 2.83kVDC is applied for one second. 0.25 0.34 0.43 20 V V V VRMS Note 4: The LTM8068E is guaranteed to meet performance specifications from 0C to 125C. Specifications over the -40C to 125C internal temperature range are assured by design, characterization and correlation with statistical process controls. LTM8068I is guaranteed to meet specifications over the full -40C to 125C 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 5: VRUN = 0V (Flyback not running), but the VOUT2 post regulator is powered by applying a voltage to VOUT1. 8068fb For more information www.linear.com/LTM8068 3 LTM8068 TYPICAL PERFORMANCE CHARACTERISTICS as in Table 1 (TA = 25C). 80 50 0 50 100 150 200 250 LOAD CURRENT (mA) 300 60 50 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 40 40 350 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 0 50 75 200 300 400 LOAD CURRENT (mA) 45 500 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 0 50 100 150 200 LOAD CURRENT (mA) 250 25 0 VIN 5V VIN==5V 12V VIN VIN==12V 24V VIN VIN==24V 36V VIN VIN==36V 0 50 100 150 200 250 LOAD CURRENT (mA) 300 350 8068 G07 4 500 65 VIN = 5V VIN = 12V VIN = 24V 0 50 100 150 200 LOAD CURRENT (mA) 250 8068 G06 Input Current vs Load Current, VOUT1 = 3.3V 300 Input Current vs Load Current, VOUT1 = 5V 240 75 50 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 25 0 600 75 55 300 100 INPUT CURRENT (mA) INPUT CURRENT (mA) 125 50 200 300 400 LOAD CURRENT (mA) 8068 G05 Input Current vs Load Current, VOUT1 = 2.5 75 100 Input Current vs Load Current, VOUT1 = 15V 65 8068 G04 100 0 85 55 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 100 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 8068 G03 EFFICIENCY (%) 75 EFFICIENCY (%) EFFICIENCY (%) 85 0 40 Efficiency vs Load Current, VOUT1 = 12V 85 45 60 8068 G02 Efficiency vs Load Current, VOUT1 = 8V 55 70 50 100 150 200 250 300 350 400 LOAD CURRENT (mA) 8068 G01 65 Efficiency vs Load Current, VOUT1 = 5V 80 EFFICIENCY (%) 60 30 90 70 EFFICIENCY (%) EFFICIENCY (%) 70 Efficiency vs Load Current, VOUT1 = 3.3V 0 100 200 300 LOAD CURRENT (mA) 400 8068 G08 INPUT CURRENT (mA) 80 Efficiency vs Load Current, VOUT1 = 2.5V Unless otherwise noted, operating conditions are 180 120 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 60 0 0 100 200 300 400 LOAD CURRENT (mA) 500 600 8068 G09 8068fb For more information www.linear.com/LTM8068 LTM8068 TYPICAL PERFORMANCE CHARACTERISTICS as in Table 1 (TA = 25C). 300 200 100 0 0 100 200 300 400 LOAD CURRENT (mA) 400 200 100 0 100 200 LOAD CURRENT (mA) 8068 G10 50 0 10 20 VIN (V) 30 270 180 0 40 Maximum Load Current vs VIN 600 2.5VOUT1 3.3VOUT1 200 0 10 20 VIN (V) 0 10 8068 G13 300 100 500 90 MAXIMUM LOAD CURRENT (mA) MAXIMUM LOAD CURRENT (mA) 400 Input Current vs VIN, VOUT2 Shorted 360 INPUT CURRENT (mA) INPUT CURRENT (mA) 200 0 30 40 8068 G16 100 VIN = 5V VIN = 12V VIN = 24V 0 100 200 LOAD CURRENT (mA) 300 20 VIN (V) 30 200 20 VIN (V) 250 125 300 5VOUT1 8VOUT1 10 VV 5V ININ==5V 12V VV ININ==12V 24V VV ININ==24V 0 5 10 15 VOUT1 (V) 8068 G14 Maximum Load Current vs VIN 0 Maximum Load Current vs VOUT1 375 0 40 400 0 8068 G12 MAXIMUM LOAD CURRENT (mA) 450 100 200 8068 G11 Input Current vs VIN, VOUT1 Shorted, VOUT2 Open 150 Input Current vs Load Current, VOUT1 = 15V 300 0 300 MAXIMUM LOAD CURRENT (mA) 250 400 VIN = 5V VIN = 12V VIN = 24V VIN = 36V 300 0 500 Input Current vs Load Current, VOUT1 = 12V INPUT CURRENT (mA) VIN = 5V VIN = 12V VIN = 24V VIN = 36V INPUT CURRENT (mA) INPUT CURRENT (mA) 400 Input Current vs Load Current, VOUT1 = 8V Unless otherwise noted, operating conditions are 30 40 8068 G17 20 25 8068 G15 Maximum Load Current vs VIN 12VOUT1 15VOUT1 200 100 0 0 10 20 VIN (V) 30 40 8068 G18 8068fb For more information www.linear.com/LTM8068 5 LTM8068 TYPICAL PERFORMANCE CHARACTERISTICS as in Table 1 (TA = 25C). Minimum Load Current vs VOUT1 Over Full Input Voltage Range Output Noise and Ripple DC2358A, 200mA Load Current Frequency vs VOUT1 Load Current Stock DC2358A Demo Board 450 C9 = 470pF HP461 150MHz AMPLIFIER AT 40dB GAIN 20 15 VOUT1 20mV/DIV 10 VOUT2 500V/DIV 5 2s/DIV 6 12 18 VOUT1 (V) MAXIMUM LOAD CURRENT (mA) VOUT2 DROPOUT VOLTAGE (V) Derating, 1.2VOUT2 400 125C 0.5 25C 0.4 0.3 -40C 0.2 0.1 0 50 100 150 200 250 VOUT2 LOAD CURRENT (mA) 100 300 MAXIMUM LOAD CURRENT (mA) 100 VIN = 5V VIN = 12V VIN = 24V, 36V 50 75 100 AMBIENT TEMPERATURE ( C) 125 8068 G25 200 300 400 LOAD CURRENT (mA) 500 600 25 50 75 100 AMBIENT TEMPERATURE ( C) 200 100 0 125 0LFM AIRFLOW 300 VIN = 5V VIN = 12V VIN = 24V, 36V 25 50 75 100 AMBIENT TEMPERATURE ( C) Derating,3.3VOUT2 400 0LFM AIRFLOW 300 200 100 0 VIN = 5V VIN = 12V VIN = 24V, 36V 25 50 75 100 AMBIENT TEMPERATURE ( C) 125 8068 G24 Derating, 2.5VOUT2 400 200 6 100 8068 G23 0LFM AIRFLOW 25 VIN = 5V VIN = 12V VIN = 24V, 36V 8058 G22 300 0 0LFM AIRFLOW 200 Derating, 1.8VOUT2 400 0 Derating, 1.5VOUT2 400 300 0 0 VIN = 5V VIN = 12V VIN = 24V 8068 G21 VOUT2 = 3.3V 0.6 250 8068 G19 VOUT2 Dropout 0.7 350 150 24 MAXIMUM LOAD CURRENT (mA) 0 MAXIMUM LOAD CURRENT (mA) 0 8068 G20 SWITCHING FREQUENCY (kHz) MINIMUM LOAD CURRENT (mA) 25 MAXIMUM LOAD CURRENT (mA) Unless otherwise noted, operating conditions are 125 8068 G26 0LFM AIRFLOW 300 200 100 0 VIN = 5V VIN = 12V VIN = 24V, 36V 25 50 75 100 AMBIENT TEMPERATURE ( C) 125 8068 G27 8068fb For more information www.linear.com/LTM8068 LTM8068 TYPICAL PERFORMANCE CHARACTERISTICS as in Table 1 (TA = 25C). 400 MAXIMUM LOAD CURRENT (mA) 0LFM AIRFLOW 300 200 100 25 50 75 100 AMBIENT TEMPERATURE ( C) 125 300 0LFM AIRFLOW 300 200 100 0 VIN = 5V VIN = 12V VIN = 24V, 36V 25 8068 G28 50 75 100 AMBIENT TEMPERATURE ( C) Derating, 15VOUT2 250 200 150 100 0 VIN = 5V VIN = 12V VIN = 24V 25 0LFM AIRFLOW 200 100 0 VIN = 5V VIN = 12V VIN = 24V, 32V 25 50 75 100 AMBIENT TEMPERATURE ( C) 125 8068 G30 Derating, 18VOUT2 200 0LFM AIRFLOW 50 125 Derating, 12VOUT2 8068 G29 MAXIMUM LOAD CURRENT (mA) 0 VIN = 5V VIN = 12V, 24V, 36V Derating, 8VOUT2 MAXIMUM LOAD CURRENT (mA) Derating, 5VOUT2 MAXIMUM LOAD CURRENT (mA) MAXIMUM LOAD CURRENT (mA) 400 Unless otherwise noted, operating conditions are 50 75 100 AMBIENT TEMPERATURE ( C) 125 0LFM AIRFLOW 150 100 50 0 VIN = 5V VIN = 12V VIN = 24V 25 50 75 100 AMBIENT TEMPERATURE ( C) 8068 G31 125 8068 G32 8068fb For more information www.linear.com/LTM8068 7 LTM8068 PIN FUNCTIONS VOUT1 (Bank 1): VOUT1 and VOUTN comprise the isolated output of the LTM8068 flyback stage. Apply an external capacitor between VOUT1 and VOUTN. Do not allow VOUTN to exceed VOUT1. VOUTN (Bank 2): VOUTN is the return for both VOUT1 and VOUT2. VOUT1 and VOUTN comprise the isolated output of the LTM8068. In most applications, the bulk of the heat flow out of the LTM8068 is through the GND and VOUTN 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. Apply an external capacitor between VOUT1 and VOUTN. VOUT2 (Bank 3): The output of the secondary side linear post regulator. Apply the load and output capacitor between VOUT2 and VOUTN. See the Applications Information section for more information on output capacitance and reverse output characteristics. GND (Bank 4): This is the local ground of the LTM8068 primary. In most applications, the bulk of the heat flow out of the LTM8068 is through the GND and VOUTN pads, so the printed circuit design has a large impact on the thermal performance of the part. See the PCB Layout and Thermal Considerations sections for more details. VIN (Bank 5): VIN supplies current to the LTM8068's internal regulator and to the integrated power switch. These pins must be locally bypassed with an external, low ESR capacitor. BYP (Pin B2): The BYP pin is used to bypass the reference of the LDO to achieve low noise performance from the linear post regulator. The BYP pin is clamped internally to 0.6V relative to VOUTN. A small capacitor from VOUT2 to this pin will bypass the reference to lower the output voltage noise. A maximum value of 0.01F can be used for reducing output voltage noise to a typical 20VRMS over a 100Hz to 100kHz bandwidth. If not used, this pin must be left unconnected. RUN (Pin F3): A resistive divider connected to VIN and this pin programs the minimum voltage at which the LTM8068 will operate. Below 1.24V, the LTM8068 does not deliver power to the secondary. When RUN is less than 1.24V, the pin draws 2.5A, allowing for a programmable hysteresis. Do not allow a negative voltage (relative to GND) on this pin. FB1 (Pin G7): Apply a resistor from this pin to GND to set the output voltage VOUT1 relative to VOUTN, using the recommended value given in Table 1. If Table 1 does not list the desired VOUT1 value, the equation ( ) RFB1 = 37.415 VOUT1-0.955 k may be used to approximate the value. To the seasoned designer, this exponential equation may seem unusual. The equation is exponential due to nonlinear current sources that are used to temperature compensate the regulation. Do not drive this pin. FB2 (Pin A2): This is the input to the error amplifier of the secondary side LDO post regulator. This pin is internally clamped to 7V. The FB2 pin voltage is 1.22V referenced to VOUTN and the output voltage range is 1.22V to 12V. Apply a resistor from this pin to VOUTN, using the equation RFB2 = 608.78/(VOUT2 - 1.22)k. If the post regulator is not used, leave this pin floating. 8 8068fb For more information www.linear.com/LTM8068 LTM8068 BLOCK DIAGRAM VOUT1 VIN VOUT2 * * 0.1F 499k 0.1F LOW NOISE LDO FB2 BYP RUN CURRENT MODE CONTROLLER VOUTN FB1 GND 8068 BD 8068fb For more information www.linear.com/LTM8068 9 LTM8068 OPERATION The LTM8068 is a stand-alone isolated flyback switching DC/DC power supply that can deliver up to 450mA of output current at 5VOUT1, 24VIN. This module provides a regulated output voltage programmable via one external resistor from 2.5V to 18V. It is also equipped with a high performance linear post regulator. The input voltage range of the LTM8068 is 2.8V to 40V. Given that the LTM8068 is a flyback converter, the output current depends upon the input and output voltages, so make sure that the input voltage is high enough to support the desired output voltage and load current. The Typical Performance Characteristics section gives several graphs of the maximum load versus VIN for several output voltages. A simplified block diagram is given. The LTM8068 contains a current mode controller, power switching element, power transformer, power Schottky diode, a modest amount of input and output capacitance, and a high performance linear post regulator. The LTM8068 has a galvanic primary to secondary isolation rating of 2kVAC. For details please refer to the Isolation, Working Voltage and Safely Compliance section. The LTM8068 is a UL 60950 recognized component. 10 The RUN pin is used to turn on or off the LTM8068, disconnecting the output and reducing the input current to 1A or less. The LTM8068 is a variable frequency device. For a given input and output voltage, the frequency decreases as the load increases. For light loads, the current through the internal transformer may be discontinuous. The post regulator is a high performance 300mA low dropout regulator with micropower quiescent current and shutdown. The device is capable of supplying 300mA at a dropout voltage of 430mV. Output voltage noise can be lowered to 20VRMS over a 100Hz to 100kHz bandwidth with the addition of a 0.01F reference bypass capacitor. Additionally, this reference bypass capacitor will improve transient response of the regulator, lowering the settling time for transient load conditions. The linear regulator is protected against both reverse input and reverse output voltages. 8068fb For more information www.linear.com/LTM8068 LTM8068 APPLICATIONS INFORMATION For most applications, the design process is straight forward, summarized as follows: 1. Look at Table 1a (or Table 1b, if the post linear regulator is used) and find the row that has the desired input range and output voltage. 2. Apply the recommended CIN, COUT1, COUT2, RFB1 and RFB2 as required. 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 may be limited by junction temperature, the relationship between the input and output voltage magnitude and polarity and other factors. Please refer to the graphs in the Typical Performance Characteristics section for guidance. Capacitor Selection Considerations The CIN, COUT1 and COUT2 capacitor values in Table 1 are the minimum recommended values for the associated operating conditions. Applying capacitor values below those indicated in Table 1 is not recommended, and may result in undesirable operation. Using larger values is generally acceptable, and can yield improved dynamic response, if it is necessary. Again, it is incumbent upon the user to verify proper operation over the intended system's line, load and environmental conditions. 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 LTM8068. A ceramic input capacitor combined with trace or cable inductance forms a high-Q (underdamped) tank circuit. If the LTM8068 circuit is plugged into a live supply, the input voltage can ring to much higher than its nominal value, possibly exceeding the device's rating. This situation is easily avoided; see the Hot-Plugging Safely section. LTM8068 Table 1a. Recommended Component Values and Configuration for Specific VOUT1 Voltages (TA = 25C) VIN VOUT1 CIN COUT1 RFB1 2.8V to 40V 2.5V 2.2F, 50V, 1206 100F, 6.3V, 1210 15.4k 2.8V to 40V 3.3V 2.2F, 50V, 1206 47F, 6.3V, 1210 11.8k 2.8V to 40V 5V 2.2F, 50V, 1206 22F, 16V, 1210 8.25k 2.8V to 37V 8V 2.2F, 50V, 1206 22F, 16V, 1210 5.23k 2.8V to 33V 12V 4.7F, 50V, 1206 10F, 50V, 1210 3.48k 2.8V to 30V 15V 4.7F, 50V, 1206 4.7F, 25V, 1210 2.8k 2.8V to 27V 18V 4.7F, 50V, 1206 4.7F, 25V, 1210 2.37k Note: An input bulk capacitor is required. 8068fb For more information www.linear.com/LTM8068 11 LTM8068 APPLICATIONS INFORMATION LTM8068 Table 1b. Recommended Component Values and Configuration for Specific VOUT2 Voltages (TA = 25C) VIN VOUT1 VOUT2 CIN COUT1 COUT2 RFB1 RFB2 2.8V to 40V 1.7V 1.2V 2.2F, 50V, 1206 100F, 6.3V, 1210 10F, 6.3V, 1206 20.5k open 2.8V to 40V 2V 1.5V 2.2F, 50V, 1206 100F, 6.3V, 1210 10F, 6.3V, 1206 18.2k 2.32M 2.8V to 40V 2.4V 1.8V 2.2F, 50V, 1206 100F, 6.3V, 1210 10F, 6.3V, 1206 15.8k 1.07M 2.8V to 40V 3.1V 2.5V 2.2F, 50V, 1206 100F, 6.3V, 1210 10F, 6.3V, 1206 12.7k 487k 2.8V to 40V 3.9V 3.3V 2.2F, 50V, 1206 47F, 6.3V, 1210 10F, 6.3V, 1206 10.5k 294k 2.8V to 38V 5.6V 5V 2.2F, 50V, 1206 22F, 16V, 1210 10F, 6.3V, 1206 7.32k 162k 2.8V to 36V 8.6V 8V 2.2F, 50V, 1206 22F, 16V, 1210 10F, 10V, 1206 4.89k 88.7k 2.8V to 32V 12.7V 12V 4.7F, 50V, 1206 10F, 50V, 1210 22F, 16V, 1206 3.32k 56.2k 2.8V to 29V 15.8V 15V 4.7F, 50V, 1206 4.7F, 25V, 1210 22F, 16V, 1206 2.67k 44.2k 2.8V to 26V 18.8V 18V 4.7F, 50V, 1206 4.7F, 25V, 1210 22F, 25V, 1206 2.26k 36.5k Note: An input bulk capacitor is required. Isolation, Working Voltage and Safety Compliance The LTM8068 isolation is 100% hi-pot tested by tying all of the primary pins together, all of the secondary pins together and subjecting the two resultant circuits to a high voltage differential for one second. This establishes the isolation voltage rating of the LTM8068 component. The isolation rating of the LTM8068 is not the same as the working or operational voltage that the application will experience. This is subject to the application's power source, operating conditions, the industry where the end product is used and other factors that dictate design requirements such as the gap between copper planes, traces and component pins on the printed circuit board, as well as the type of connector that may be used. To maximize the allowable working voltage, the LTM8068 has two columns of solder balls removed to facilitate the printed circuit board design. The ball to ball pitch is 1.27mm, and the typical ball diameter is 0.78mm. Accounting for the missing columns and the ball diameter, the printed circuit board may be designed for a metal-to-metal separation of up to 3.03mm. This may have to be reduced somewhat to allow for tolerances in solder mask or other printed circuit board design rules. For those situations where information about the spacing of LTM8068 internal circuitry is required, the minimum metal to metal separation of the primary and secondary is 0.75mm. To reiterate, the manufacturer's isolation voltage rating and the required working or operational voltage are often 12 different numbers. In the case of the LTM8068, the isolation voltage rating is established by 100% hi-pot testing. The working or operational voltage is a function of the end product and its system level specifications. The actual required operational voltage is often smaller than the manufacturer's isolation rating. The LTM8068 is a UL recognized component under UL 60950, file number E464570. The UL 60950 insulation category of the LTM8068 transformer is Functional. Considering UL 60950 Table 2N and the gap distances stated above, 3.03mm external and 0.75mm internal, the LTM8068 may be operated with up to 250V working voltage in a pollution degree 2 environment. The actual working voltage, insulation category, pollution degree and other critical parameters for the specific end application depend upon the actual environmental, application and safety compliance requirements. It is therefore up to the user to perform a safety and compliance review to ensure that the LTM8068 is suitable for the intended application. VOUT2 Post Regulator VOUT2 is produced by a high performance low dropout 300mA regulator. At full load, its dropout is less than 430mV. Its output is set by applying a resistor from the RFB2 pin to GND; the value of RFB2 can be calculated by the equation: RFB2 = 608.78 k VOUT2 - 1.22 8068fb For more information www.linear.com/LTM8068 LTM8068 APPLICATIONS INFORMATION VOUT2 Post Regulator Bypass Capacitance and Low Noise Performance PCB Layout The VOUT2 linear regulator may be used with the addition of a 0.01F bypass capacitor from VOUT to the BYP pin to lower output voltage noise. A good quality low leakage capacitor, such as a X5R or X7R ceramic, is recommended. This capacitor will bypass the reference of the regulator, lowering the output voltage noise to as low as 20VRMS. Using a bypass capacitor has the added benefit of improving transient response. Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8068. The LTM8068 is nevertheless a switching power supply, and care must be taken to minimize electrical noise to 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 1 for a suggested layout. Ensure that the grounding and heat sinking are acceptable. Safety Rated Capacitors A few rules to keep in mind are: Some applications require safety rated capacitors, which are high voltage capacitors that are specifically designed and rated for AC operation and high voltage surges. These capacitors are often certified to safety standards such as UL 60950, IEC 60950 and others. In the case of the LTM8068, a common application of a safety rated capacitor would be to connect it from GND to VOUTN. To provide maximum flexibility, the LTM8068 does not include any components between GND and VOUTN. Any safety capacitors must be added externally. The specific capacitor and circuit configuration for any application depends upon the safety requirements of the system into which the LTM8068 is being designed. Table 2 provides a list of possible capacitors and their manufacturers. The application of a capacitor from GND to VOUTN may also reduce the high frequency output noise on the output. MANUFACTURER PART NUMBER DESCRIPTION Murata Electronics 4700pF, 250V AC, X7R, 4.5mm x 3.2mm Capacitor Johanson Dielectrics 302R29W471KV3E-****-SC 470pF, 250V AC, X7R, 4.5mm x 2mm Capacitor Syfer Technology 1808JA250102JCTSP 2. Place the CIN capacitor as close as possible to the VIN and GND connections of the LTM8068. 3. Place the COUT1 capacitor as close as possible to VOUT1 and VOUTN. Likewise, place the COUT2 capacitor as close as possible to VOUT2 and VOUTN. 4. Place the CIN and COUT capacitors such that their ground current flow directly adjacent or underneath the LTM8068. FB1 VOUT1 LTM8058 COUT1 Table 2. Safety Rated Capacitors GA343DR7GD472KW01L 1. Place the RFB1 and RFB2 resistors as close as possible to their respective pins. 100pF, 250V AC, C0G, 1808 Capacitor VOUTN RUN FB2 BYP COUT2 CIN VOUT2 VIN THERMAL/INTERCONNECT VIAS 8068 F01 Figure 1. Layout Showing Suggested External Components, Planes and Thermal Vias 8068fb For more information www.linear.com/LTM8068 13 LTM8068 APPLICATIONS INFORMATION 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 LTM8068. 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 1. The LTM8068 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. Minimum Load Due to the nature of the flyback regulator in general, and the LTM8068 control scheme specifically, the LTM8068 requires a minimum load for proper operation. Otherwise, the output may go out of regulation if the load is too light. The most common way to address this is to place a resistor across the output. The Minimum Load Current vs VOUT Over Full Output Voltage Range graph in the Typical Performance Characteristics section of may be used as a guide in selecting the resistor. Note that this graph describes room temperature operation. If the end application operates at a colder temperature, the minimum load requirement may be higher and the minimum load condition must be characterized for the lowest operating temperature. If it is impractical to place a resistive load permanently across the output, a resistor and Zener diode may be used instead, as shown in Figure 2. While the minimum load resistor mentioned in the prior paragraph will always draw current while the LTM8068 output is powered, the series resistor-Zener diode combination will only draw current if the output is too high. When using this circuit, take care to ensure that the characteristics of the Zener diode are appropriate for the intended application's temperature range. 14 VOUTP LTM8068 VOUTN 8068 F02 Figure 2: Use a Resistor and Zener Diode to Meet the Minimum Load Requirement Hot-Plugging Safely The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of the LTM8068. However, these capacitors can cause problems if the LTM8068 is plugged into a live supply (see Linear Technology Application Note 88 for a complete discussion). The low loss ceramic capacitor combined with stray inductance in series with the power source forms an underdamped tank circuit, and the voltage at the VIN pin of the LTM8068 can ring to more than twice the nominal input voltage, possibly exceeding the LTM8068's rating and damaging the part. If the input supply is poorly controlled or the user will be plugging the LTM8068 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 adding 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 can be a large component in the circuit. Thermal Considerations The LTM8068 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 LTM8068 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 8068fb For more information www.linear.com/LTM8068 LTM8068 APPLICATIONS INFORMATION operation over the intended system's line, load and environmental operating conditions. For increased accuracy and fidelity to the actual application, many designers use FEA to predict thermal performance. To that end, the Pin Configuration section of the data sheet typically gives four thermal coefficients: JA: Thermal resistance from junction to ambient JCbottom: Thermal resistance from junction to the bottom of the product case JCtop: Thermal resistance from junction to top of the product case JCboard: 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 as follows: JA 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. JCbottom is the junction-to-board thermal resistance with all of the component power dissipation flowing through the bottom of the package. In the typical Module converter, 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. JCtop is determined with nearly all of the component power dissipation flowing through the top of the package. As the electrical connections of the typical Module converter 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 JCbottom, this value may be useful for comparing packages but the test conditions don't generally match the user's application. JCboard is the junction-to-board thermal resistance where almost all of the heat flows through the bottom of the Module converter and into the board, and is really the sum of the JCbottom and the thermal resistance of the bottom of the part through the solder joints and through a portion of the board. The board temperature is measured a specified distance from the package, using a two-sided, two-layer board. This board is described in JESD 51-9. Given these definitions, it should now be apparent that none of these thermal coefficients reflects an actual physical operating condition of a Module converter. 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 3. The blue resistances are contained within the Module converter, and the green are outside. The die temperature of the LTM8068 must be lower than the maximum rating of 125C, so care should be taken in the layout of the circuit to ensure good heat sinking of the LTM8068. The bulk of the heat flow out of the LTM8068 is through the bottom of the module and the BGA 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. 8068fb For more information www.linear.com/LTM8068 15 LTM8068 APPLICATIONS INFORMATION JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD) CASE (TOP)-TO-AMBIENT RESISTANCE JUNCTION-TO-CASE (TOP) RESISTANCE JUNCTION-TO-BOARD RESISTANCE JUNCTION AMBIENT JUNCTION-TO-CASE CASE (BOTTOM)-TO-BOARD (BOTTOM) RESISTANCE RESISTANCE BOARD-TO-AMBIENT RESISTANCE 8068 F03 MODULE DEVICE Figure 3. Approximate Thermal Model of LTM8068 TYPICAL APPLICATIONS 3.3V Flyback Converter VOUT2 Maximum Load Current vs VIN 350 RUN * 2.2F (3.9V) 47F VOUT2 * LOW NOISE LDO VOUT2 3.3V 300mA MAX FB2 VOUTN 294k 10F FB1 10.5k LTM8068 GND LOAD CURRENT (mA) VOUT1 VIN VIN 2.8V TO 40V 250 150 8068 TA02a 50 PIN BYP IS NOT USED IN THIS SCHEMATIC 12V Flyback Converter with Low Noise Bypass 0 10 20 VIN (V) 30 40 8068 TA02b VOUT2 Maximum Load Current vs VIN 250 VOUT1 RUN 4.7F * (12.7V) 10F VOUT2 * FB1 LOW NOISE LDO 0.01F BYP FB2 VOUTN 3.32k GND LTM8068 VOUT2 12V 240mA MAX 22F 56.2k LOAD CURRENT (mA) VIN VIN 2.8V TO 32V 200 150 100 8068 TA03a 50 16 0 8 16 VIN (V) 24 32 8068 TA03b 8068fb For more information www.linear.com/LTM8068 LTM8068 PACKAGE DESCRIPTION Pin Assignment Table (Arranged by Pin Number) PIN FUNCTION PIN FUNCTION PIN FUNCTION PIN FUNCTION PIN FUNCTION PIN FUNCTION B1 VOUT2 C1 D1 E1 GND F1 A1 VOUT2 A2 FB2 B2 BYP C2 D2 E2 GND F2 A3 VOUTN B3 VOUTN C3 D3 E3 GND F3 RUN B4 VOUTN C4 D4 E4 GND F4 GND A4 VOUTN B5 VOUTN C5 D5 E5 GND F5 GND A5 VOUTN B6 VOUT1 C6 D6 E6 GND F6 GND A6 VOUT1 B7 VOUT1 C7 D7 E7 GND F7 GND A7 VOUT1 PIN G1 G2 G3 G4 G5 G6 G7 FUNCTION PIN VIN H1 VIN H2 H3 GND H4 GND H5 GND H6 FB1 H7 FUNCTION VIN VIN GND GND GND GND PACKAGE PHOTO 8068fb For more information www.linear.com/LTM8068 17 4 For more information www.linear.com/LTM8068 E SUGGESTED PCB LAYOUT TOP VIEW 2.540 PACKAGE TOP VIEW 1.270 PIN "A1" CORNER 0.3175 0.000 0.3175 aaa Z 1.270 Y 4.445 3.175 1.905 0.635 0.000 0.635 1.905 3.175 4.445 D X 4.7625 4.1275 aaa Z 3.95 - 4.05 SYMBOL A A1 A2 b b1 D E e F G aaa bbb ccc ddd eee NOM 4.92 0.60 4.32 0.75 0.63 11.25 9.0 1.27 8.89 7.62 DIMENSIONS 0.15 0.10 0.20 0.30 0.15 MAX 5.12 0.70 4.42 0.90 0.66 NOTES DETAIL B PACKAGE SIDE VIEW TOTAL NUMBER OF BALLS: 38 MIN 4.72 0.50 4.22 0.60 0.60 DETAIL A b1 0.27 - 0.37 SUBSTRATE A1 ddd M Z X Y eee M Z DETAIL B MOLD CAP ccc Z A2 A Z (Reference LTC DWG # 05-08-1925 Rev A) Ob (38 PLACES) // bbb Z 18 2.540 b 3 F e SEE NOTES 7 5 4 3 2 1 DETAIL A PACKAGE BOTTOM VIEW 6 G H G F E D C B A PIN 1 DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE 4 7 TRAY PIN 1 BEVEL ! BGA 38 1212 REV A PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX Module PACKAGE ROW AND COLUMN LABELING MAY VARY AMONG Module PRODUCTS. REVIEW EACH PACKAGE LAYOUT CAREFULLY 6. SOLDER BALL COMPOSITION IS 96.5% Sn/3.0% Ag/0.5% Cu 5. PRIMARY DATUM -Z- IS SEATING PLANE BALL DESIGNATION PER JESD MS-028 AND JEP95 3 2. ALL DIMENSIONS ARE IN MILLIMETERS 7 SEE NOTES NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 COMPONENT PIN "A1" BGA Package 38-Lead (11.25mm x 9.00mm x 4.92mm) LTM8068 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LTM8068#packaging for the most recent package drawings. 8068fb 3.810 3.810 LTM8068 REVISION HISTORY REV DATE DESCRIPTION A 05/16 Corrected symbol of internal switch on Block Diagram from NPN transistor to N-channel MOSFET PAGE NUMBER 9 B 07/17 Added Minimum Load section 14 8068fb 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 itsinformation circuits as described herein will not infringe on existing patent rights. For more www.linear.com/LTM8068 19 LTM8068 TYPICAL APPLICATION Maximum Load Current vs VIN 3.3V, 2.5V Dual Output Converter with Low Noise Bypass VOUT1 RUN * 2.2F * BYP FB2 10F 487k VOUTN GND VOUT2 2.5V 300mA MAX 0.01F FB1 11.8k 100F VOUT2 LOW NOISE LDO LTM8068 400 VOUT1 3.3V LOAD CURRENT (mA) VIN VIN 2.8V TO 40V VOUT2 VOUT1 300 200 8068 TA04a 100 0 8 16 VIN (V) 24 32 8068 TA04b DESIGN RESOURCES SUBJECT DESCRIPTION Module Design and Manufacturing Resources Design: * Selector Guides * Demo Boards and Gerber Files * Free Simulation Tools Module Regulator Products Search 1. Sort table of products by parameters and download the result as a spread sheet. Manufacturing: * Quick Start Guide * PCB Design, Assembly and Manufacturing Guidelines * Package and Board Level Reliability 2. Search using the Quick Power Search parametric table. TechClip Videos Quick videos detailing how to bench test electrical and thermal performance of Module products. Digital Power System Management Linear Technology's family of digital power supply management ICs are highly integrated solutions that offer essential functions, including power supply monitoring, supervision, margining and sequencing, and feature EEPROM for storing user configurations and fault logging. 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