LTM8022 1A, 36V DC/DC µModule FEATURES DESCRIPTION n The LTM®8022 is a complete 1A, DC/DC step-down power supply. Included in the package are the switching controller, power switches, inductor, and all support components. Operating over an input voltage range of 3.6V to 36V, the LTM8022 supports an output voltage range of 0.8V to 10V, and a switching frequency range of 200kHz to 2.4MHz, each set by a single resistor. Only the bulk input and output filter capacitors are needed to finish the design. n n n n n n n n Complete Step-Down Switch Mode Power Supply Wide Input Voltage Range: 3.6V to 36V 0.8V to 10V Output Voltage 1A Output Current Adjustable Switching Frequency: 200kHz to 2.4MHz Current Mode Control (e4) RoHS Compliant Package with Gold Pad Finish Programmable Soft-Start Tiny, Low Profile (11.25mm × 9mm × 2.82mm) Surface Mount LGA Package APPLICATIONS n 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 LTM8022 is packaged in a thermally enhanced, compact (11.25mm × 9mm) and low profile (2.82mm) overmolded Land Grid Array (LGA) package suitable for automated assembly by standard surface mount equipment. The LTM8022 is RoHS compliant. Automotive Battery Regulation Power for Portable Products Distributed Supply Regulation Industrial Supplies Wall Transformer Regulation , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. μModule is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 7VIN to 36VIN , 5V/1A μModuleTM Regulator VIN* 7V TO 36V VIN 100 VOUT 5V 1A VOUT LTM8022 AUX RUN/SS 2.2μF Efficiency and Power Loss 0.8 VIN = 12V 0.7 90 4.7μF 0.6 EFFICIENCY (%) BIAS PG RT GND SYNC ADJ 70 0.5 EFFICIENCY POWER LOSS 60 0.4 0.3 50 29.4k 0.2 93.1k 40 8022 TA01a *RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION FOR START-UP DETAILS 30 0.001 POWER LOSS (W) 80 SHARE 0.1 0.1 0.01 LOAD CURRENT (A) 1 0 8022 TA01b 8022fb 1 LTM8022 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (See Table 3, Pin Assignment) (Note 1) VIN, RUN/SS Voltage .................................................40V ADJ, RT, SHARE, Voltage .............................................5V VOUT , AUX .................................................................10V SYNC, PG ..................................................................30V BIAS ..........................................................................16V VIN + BIAS .................................................................56V Internal Operating Temperature.............. –40°C to 125°C Solder Temperature............................................... 250°C Storage Temperature.............................. –55°C to 125°C GND (BANK 3) SHARE RT ADJ 7 6 SYNC PG 5 RUN/SS BIAS 4 AUX 3 VOUT (BANK 2) 2 VIN (BANK 1) 1 A B C D E F G H LGA Package 50-Lead (11.25mm s 9mm s 2.82mm) TJMAX = 125°C, θJA = 24°C/W θJA DERIVED FROM 6.6cm × 5cm 4-LAYER PCB, WEIGHT = 0.93g ORDER INFORMATION LEAD FREE FINISH PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE (Note 2) LTM8022EV#PBF LTM8022V 50-Pin (11.25mm × 9mm × 2.82mm) LGA –40°C to 85°C LTM8022IV#PBF LTM8022V 50-Pin (11.25mm × 9mm × 2.82mm) LGA –40°C to 85°C LTM8022MPV#PBF LTM8022MPV 50-Pin (11.25mm × 9mm × 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. Consult LTC Marketing for information on non-standard lead based finish parts. 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://linear.com/packaging/ 8022fb 2 LTM8022 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 10V, VRUN/SS = 10V, VBIAS = 3V, RT = 60.4kΩ, CIN = 2.2μF, COUT = 4.7μF, unless otherwise specified. (Note 2) SYMBOL PARAMETER CONDITIONS MIN VIN Input DC Voltage VOUT Output DC Voltage 0V < IOUT < 1A, RADJ Open 0V < IOUT < 1A, RADJ = 43.2k RADJ(MIN) Minimum Allowable RADJ (Note 3) IOUT(MAX) Continuous Output DC Current 4V < VIN < 36V, COUT = 51μF (Note 4) IQVIN VIN Quiescent Current VRUN/SS = 0.2V, RT = 174k VBIAS = 3V, Not Switching, RT = 174k (E, I) VBIAS = 3V, Not Switching, RT = 174k (MP) VBIAS = 0V, Not Switching, RT = 174k l l IQBIAS BIAS Quiescent Current VRUN/SS = 0.2V, RT = 174k VBIAS = 3V, Not Switching, RT = 174k (E, I) VBIAS = 3V, Not Switching, RT = 174k (MP) VBIAS = 0V, Not Switching, RT = 174k l l ΔVOUT/VOUT Line Regulation 3.6V < VIN < 36V, IOUT = 1A, VOUT = 3.3V 0.1 % ΔVOUT/VOUT Load Regulation VIN = 24V, 0V < IOUT < 1A, VOUT = 3.3V, COUT = 51μF 0.4 % VOUT(AC_RMS) Output Ripple (RMS) VIN = 24V, IOUT = 1A, VOUT = 3.3V, COUT = 51μF 10 mV fSW Switching Frequency RT = 113kΩ, COUT = 51μF 325 kHz ISC(OUT) Output Short-Circuit Current VIN = 36V, VOUT = 0V l TYP 3.6 36 0.8 10 COUT = 51μF 1 A 0.1 25 25 85 0.5 60 350 120 μA μA μA μA 0.03 50 50 1 0.5 120 200 5 μA μA μA μA 3 765 V kΩ 0 l UNITS V V 42.2 VADJ Voltage at ADJ Pin VBIAS(MIN) Minimum BIAS Voltage for Proper Operation IADJ Current Out of ADJ Pin ADJ = 1V, COUT = 51μF 2 IRUN/SS RUN/SS Pin Current VRUN/SS = 2.5V 5 VIH(RUN/SS) RUN/SS Input High Voltage COUT = 51μF VIL(RUN/SS) RUN/SS Input Low Voltage COUT = 51μF VPG(TH) PG Threshold VFB Rising 730 IPGO PG Leakage VPG = 30V 0.1 IPG(SINK) PG Sink Current VPG = 0.4V 200 VSYNC(IL) SYNC Low Threshold fSYNC = 550kHz, COUT = 51μF 0.5 VSYNC(IH) SYNC High Threshold fSYNC = 550kHz, COUT = 51μF ISYNC(BIAS) SYNC Pin Bias Current VSYNC = 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: The LTM8022E is guaranteed to meet performance specifications from 0°C to 85°C ambient. Specifications over the full –40°C to 85°C ambient operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTM8022I is guaranteed to meet specifications over the full –40°C to 85°C MAX A 790 805 mV 1.9 2.4 V μA 10 2.5 μA V 0.2 V mV 1 800 μA μA V 0.7 0.1 V μA ambient operating temperature range. The LTM8022MP is guaranteed to meet specifications over the full –55°C to 125°C 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 3: Guaranteed by design. Note 4: COUT = 51μF is composed of a 4.7μF ceramic capacitor and a 47μF electrolytic. 8022fb 3 LTM8022 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load (8VOUT) Efficiency vs Load (5VOUT) 95 Efficiency vs Load (3.3VOUT) 90 90 12VIN 12VIN 90 80 80 EFFICIENCY (%) 36VIN 36VIN 75 80 36VIN 75 70 75 70 65 70 65 60 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 OUTPUT CURRENT (A) 12VIN 24VIN 24VIN EFFICIENCY (%) 85 5VIN 85 85 24VIN EFFICIENCY (%) (TA = 25°C, unless otherwise noted) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 OUTPUT CURRENT (A) 8022 G01 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 OUTPUT CURRENT (A) 8022 G03 8022 G02 Output Start-up Waveform VIN = 36V, 3.3VOUT, IOUT = 1A Output Start-up Waveform VIN = 36V, 5VOUT, IOUT = 1A Minimum Required Input Voltage vs Output Voltage, IOUT = 1A 12 VOUT 2V/DIV 11 10 INPUT VOLTAGE (V) 9 8 7 VOUT 2V/DIV IIN 0.2A/DIV IIN 0.2A/DIV RUN/SS 5V/DIV RUN/SS 5V/DIV 6 8022 G05 50μs/DIV 8022 G06 50μs/DIV 5 4 3 2 0 2 4 6 8 OUTPUT VOLTAGE (V) 10 8022 G04 Input Current vs Output Current (8VOUT) Input Current vs Output Current (3.3VOUT) Input Current vs Output Current (5VOUT) 800 700 500 900 450 800 500 12VIN 400 24VIN 300 200 700 350 300 250 12VIN 200 24VIN 150 100 36VIN INPUT CURRENT (mA) 600 INPUT CURRENT (mA) INPUT CURRENT (mA) 400 600 500 300 50 100 0 0 0 200 400 800 600 OUTPUT CURRENT (mA) 1000 8022 G07 12VIN 200 36VIN 100 0 5VIN 400 24VIN 36VIN 0 200 600 800 400 OUTPUT CURRENT (mA) 1000 8022 G08 0 800 200 600 400 OUTPUT CURRENT (mA) 1000 8022 G09 8022fb 4 LTM8022 TYPICAL PERFORMANCE CHARACTERISTICS BIAS Quiescent Current vs Load Current 16 3000 14 2800 12 2600 2400 2200 6 2 1600 0 40 30 8VOUT 5VOUT 1800 20 1000 8 4 10 1200 10 2000 0 Minimum Required Input Voltage vs Output Load (8VOUT) LOAD CURRENT (mA) 3200 BIAS CURRENT (mA) OUTPUT CURRENT (mA) Output Current vs Input Voltage (Output Short) (TA = 25°C, unless otherwise noted) 3.3VOUT 600 400 200 200 0 INPUT VOLTAGE (V) 25°C 85°C 0 400 800 600 LOAD CURRENT (mA) 0 1000 10 Minimum Required Input Voltage vs Output Load (5VOUT) 1200 1000 1000 LOAD CURRENT (mA) 1200 800 600 400 8022 G13 800 600 400 200 25°C 85°C 0 0 10 20 30 INPUT VOLTAGE (V) 25°C 85°C 0 40 0 10 20 30 INPUT VOLTAGE (V) 8022 G14 Temperature Rise vs Load (3.3VOUT) 15 36VIN 10 12VIN 24VIN 5 Temperature Rise vs Load (8VOUT) 35 40 30 35 TEMPERATURE RISE (°C) TEMPERATURE RISE (°C) TEMPERATURE RISE (°C) 20 25 20 36VIN 15 12VIN 10 24VIN 5 200 400 600 800 LOAD (mA) 1000 1200 8022 G16 40 8022 G15 Temperature Rise vs Load (5VOUT) 25 0 40 Minimum Required Input Voltage vs Output Load (3.3VOUT) 200 0 20 30 INPUT VOLTAGE (V) 8022 G11 8022 G10 LOAD CURRENT (mA) 800 30 25 24VIN 36VIN 20 15 12VIN 10 5 0 0 0 200 400 800 600 LOAD (mA) 1000 1200 8022 G17 0 200 400 800 600 LOAD (mA) 1000 1200 8022 G18 8022fb 5 LTM8022 PIN FUNCTIONS VIN (Bank 1): The VIN pin supplies current to the LTM8022’s internal regulator and to the internal power switch. This pin must be locally bypassed with an external, low ESR capacitor of at least 2.2μF. VOUT (Bank 2): Power Output Pins. Apply the output filter capacitor and the output load between these pins and GND pins. AUX (Pin F5): Low current voltage source for BIAS. In many designs, the BIAS pin is simply connected to VOUT . The AUX pin is internally connected to VOUT and is placed adjacent to the BIAS pin to ease printed circuit board routing. Although this pin is internally connected to VOUT , do NOT connect this pin to the load. If this pin is not tied to BIAS, leave it floating. The Application Information section gives specific information about the BIAS and AUX connections BIAS (Pin G5): The BIAS pin connects to the internal power bus. Connect to a power source greater than 2.4V. If the output is greater than 2.4V, connect this pin there. If the output voltage is less, connect this to a voltage source between 2.4V and 30V. Also, make sure that BIAS + VIN is less than 56V. RUN/SS (Pin H5): Tie RUN/SS pin to ground to shut down the LTM8022. Tie to 2.5V or more for normal operation. If the shutdown feature is not used, tie this pin to the VIN pin. RUN/SS also provides a soft-start function; see the Applications Information section. RT (Pin G7): The RT pin is used to program the switching frequency of the LTM8022 by connecting a resistor from this pin to ground. The Applications Information section of the data sheet includes a table to determine the resistance value based on the desired switching frequency. Minimize capacitance at this pin. SHARE (Pin F7): Tie this to the SHARE pin of another LTM8022 when paralleling the outputs. Otherwise, leave this pin floating. SYNC (Pin G6): External Clock Synchronization Input. Ground this pin for low ripple Burst Mode® operation at low output loads, or connect to a stable voltage source above 0.7V to disable Burst Mode operation. Do not leave this pin floating. Tie to a clock source for synchronization. Clock edges should have rise and fall times faster than 1μs. See Synchronization in the Applications Information section. PG (Pin H6): Open Collector Output of an Internal Comparator. PG remains low until the ADJ pin is within 10% of the final regulation voltage. PG output is valid when VIN is above 3.6V and RUN/SS is high. If this function is not used, leave this pin floating. ADJ (Pin H7): The LTM8022 regulates its ADJ pin to 0.79V. Connect the adjust resistor from this pin to ground. The value of RADJ is given by the equation, RADJ = 394.21/(VOUT – 0.79), where RADJ is in kΩ. Burst Mode is a registered trademark of Linear Technology Corporation. GND (Bank 3): Tie these GND pins to a local ground plane below the LTM8022 and the circuit components. Return the feedback divider (RADJ) to this pin. 8022fb 6 LTM8022 BLOCK DIAGRAM VIN VOUT 4.7μH 0.1μF 4.7pF 499k 10μF AUX BIAS SHARE RUN/SS CURRENT MODE CONTROLLER PG SYNC GND RT ADJ 8022 BD OPERATION The LTM8022 is a standalone non-isolated step-down switching DC/DC power supply. It can deliver up to 1A of DC output current with only bulk external input and output capacitors. This module provides a precisely regulated output voltage programmable via one external resistor from 0.8VDC to 10VDC. The input voltage range is 3.6V to 36V. Given that the LTM8022 is a step-down converter, make sure that the input voltage is high enough to support the desired output voltage and load current. A simplified Block Diagram is shown above. The LTM8022 contains a current mode controller, power switching element, power inductor, power Schottky diode and a modest amount of input and output capacitance. The LTM8022 is a fixed frequency PWM regulator. The switching frequency is set by simply connecting the appropriate value resistor from the RT pin to GND. An internal regulator provides power to the control circuitry. The bias regulator normally draws power from the VIN pin, but if the BIAS pin is connected to an external voltage higher than 2.4V, bias power will be drawn from the external source (typically the regulated output voltage). This improves efficiency. The RUN/SS pin is used to place the LTM8022 in shutdown, disconnecting the output and reducing the input current to less than 1μA. To further optimize efficiency, the LTM8022 automatically switches to Burst Mode operation in light load situations. Between bursts, all circuitry associated with controlling the output switch is shut down reducing the input supply current to 50μA in a typical application. The oscillator reduces the LTM8022’s operating frequency when the voltage at the ADJ pin is low. This frequency foldback helps to control the output current during start-up and overload. The LTM8022 contains a power good comparator which trips when the ADJ pin is at 92% of its regulated value. The PG output is an open-collector transistor that is off when the output is in regulation, allowing an external resistor to pull the PG pin high. Power good is valid when the LTM8022 is enabled and VIN is above 3.6V. 8022fb 7 LTM8022 APPLICATIONS INFORMATION Table 1. Recommended Component Values and Configuration VIN* VOUT CIN COUT RADJ BIAS fOPTIMAL(kHz) 3.6V to 36V 0.82V 2.2μF 247μF 1206 13M ≥2.4V, <16V 250 3.6V to 36V 1V 2.2μF 200μF 1206 1.87M ≥2.4V, <16V 300 3.6V to 36V 1.2V 2.2μF 100μF 1206 953k ≥2.4V, <16V 325 3.6V to 36V 1.5V 2.2μF 100μF 1206 549k ≥2.4V, <16V 375 3.6V to 36V 1.8V 2.2μF 68μF 1206 383k ≥2.4V, <16V 450 3.8V to 36V 2V 2.2μF 47μF 1206 324k ≥2.4V, <16V 475 3.8V to 36V 2.2V 2.2μF 47μF 0805 274k ≥2.4V, <16V 525 3.8V to 36V 2.5V 2.2μF 47μF 0805 226k ≥2.4V, <16V 575 4.75V to 36V 3.3V 2.2μF 22μF 0805 154k AUX 750 6.8V to 36V 5V 2.2μF 4.7μF 1206 93.1k AUX 1000 11.5V to 36V 8V 2.2μF 4.7μF 0805 53.6k AUX 1200 3.6V to 15V 0.82V 2.2μF 200μF 1206 13M VIN 500 3.6V to 15V 1V 2.2μF 147μF 1206 1.87M VIN 615 3.6V to 15V 1.2V 2.2μF 100μF 1206 953k VIN 650 3.6V to 15V 1.5V 2.2μF 100μF 1206 549k VIN 700 3.6V to 15V 1.8V 2.2μF 68μF 1206 383k VIN 800 3.6V to 15V 2V 2.2μF 47μF 1206 324k VIN 800 3.6V to 15V 2.2V 2.2μF 47μF 0805 274k VIN 850 3.6V to 15V 2.5V 2.2μF 47μF 0805 226k VIN 950 4.75V to 15V 3.3V 2.2μF 22μF 0805 154k AUX 950 6.8V to 15V 5V 2.2μF 4.7μF 1206 93.1k AUX 1150 11.5V to 15V 8V 2.2μF 4.7μF 0805 53.6k AUX 1200 9V to 24V 0.82V 2.2μF 247μF 1206 13M ≥2.4V, <16V 375 9V to 24V 1V 2.2μF 200μF 1206 1.87M ≥2.4V, <16V 400 9V to 24V 1.2V 2.2μF 100μF 1206 953k ≥2.4V, <16V 450 9V to 24V 1.5V 2.2μF 100μF 1206 549k ≥2.4V, <16V 575 9V to 24V 1.8V 2.2μF 68μF 1206 383k ≥2.4V, <16V 650 9V to 24V 2V 2.2μF 47μF 0805 324k ≥2.4V, <16V 700 9V to 24V 2.2V 2.2μF 22μF 0805 274k ≥2.4V, <16V 775 9V to 24V 2.5V 2.2μF 22μF 0805 226k ≥2.4V, <16V 850 9V to 24V 3.3V 2.2μF 22μF 0805 154k AUX 950 9V to 24V 5V 2.2μF 4.7μF 1206 93.1k AUX 1150 11.5V to 24V 8V 2.2μF 4.7μF 0805 53.6k AUX 1200 18V to 24V 10V 2.2μF 2.2μF 0805 42.2k AUX 1250 18V to 36V 0.82V 2.2μF 247μF 1206 13M ≥2.4V, <16V 250 18V to 36V 1V 2.2μF 200μF 1206 1.87M ≥2.4V, <16V 300 18V to 36V 1.2V 2.2μF 100μF 1206 953k ≥2.4V, <16V 325 18V to 36V 1.5V 2.2μF 100μF 1206 549k ≥2.4V, <16V 375 18V to 36V 1.8V 2.2μF 68μF 1206 383k ≥2.4V, <16V 450 18V to 36V 2V 2.2μF 47μF 0805 324k ≥2.4V, <16V 475 18V to 36V 2.2V 2.2μF 22μF 0805 274k ≥2.4V, <16V 525 18V to 36V 2.5V 2.2μF 22μF 0805 226k ≥2.4V, <16V 575 18V to 36V 3.3V 2.2μF 22μF 0805 154k AUX 750 18V to 36V 5V 2.2μF 4.7μF 1206 93.1k AUX 1000 18V to 36V 8V 2.2μF 4.7μF 0805 53.6k AUX 1200 18V to 36V 10V 2.2μF 2.2μF 0805 42.2k AUX 1250 4.75V to 32V –3.3V 2.2μF 22μF 0805 154k AUX 700 7V to 31V –5V 2.2μF 10μF 0805 93.1k AUX 1000 13V to 28V –8V 2.2μF 10μF 0805 53.6k AUX 1100 *Running voltage range. Please refer to Applications Information for start-up details. RT(OPTIMAL) 150k 124k 113k 93.1k 79k 73.2k 64.9k 59.0k 42.2k 29.4k 23.7k 69.8k 54.9k 49.9k 44.2k 39.2k 39.2k 36.5k 31.6k 31.6k 25.5k 23.7k 93.1k 88.7k 79.0k 59.0k 49.9k 44.2k 41.2k 36.5k 31.6k 25.5k 23.7k 22.6k 150k 124k 113k 93.1k 79k 73.2k 64.9k 59.0k 42.2k 29.4k 23.7k 22.6k 44.2k 29.4k 26.7k fMAX (kHz) 250 300 325 375 450 475 525 575 750 1050 1600 615 650 750 890 1050 1100 1200 1350 1725 2400 1900 375 400 500 575 650 700 775 850 1100 1550 2000 1450 250 300 325 375 450 475 525 575 750 1050 1600 1450 775 1075 1350 RT(MIN) 150k 124k 113k 93.1k 79k 73.2k 64.9k 59.0k 42.2k 28.0k 15.8k 54.9k 49.9k 42.2k 34.8k 28.0k 26.7k 23.7k 20.5k 14.3k 7.87k 12.1k 93.1k 88.7k 69.8k 59.0k 49.9k 44.2k 41.2k 36.5k 26.7k 16.5k 11.3k 18.2k 150k 124k 113k 93.1k 79k 73.2k 64.9k 59.0k 42.2k 28.0k 15.8k 18.2k 41.2k 27.4k 20.5k 8022fb 8 LTM8022 APPLICATIONS INFORMATION For most applications, the design process is straight forward, summarized as follows: Mode operation, the noise is typically very quiet to a casual ear. 1. In Table 1, find the row that has the desired input voltage range and output voltage. If this audible noise is unacceptable, use a high performance electrolytic capacitor at the output. The input capacitor can be a parallel combination of a 2.2μF ceramic capacitor and a low cost electrolytic capacitor. 2. Apply the recommended CIN, COUT, RADJ and RT values. 3. Connect BIAS as indicated. While these component combinations have been tested for proper operation, it is incumbent upon the user to verify proper operation over the intended system’s line, load and environmental conditions. If the desired output voltage is not listed in Table 1, set the output by applying an RADJ resistor whose value is given by the equation RADJ = 394.21/(VOUT – 0.79), where RADJ is in kΩ and VOUT is in volts. Verify the LTM8022’s operation over the system’s intended line, load and environmental conditions. 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 it is necessary. Again, it is incumbent upon the user to verify proper operation over the intended system’s line, load and environmental conditions. A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LTM8022. A ceramic input capacitor combined with trace or cable inductance forms a high Q (under damped) tank circuit. If the LTM8022 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the device’s rating. This situation is easily avoided; see the Hot-Plugging Safely section. Frequency Selection The LTM8022 uses a constant-frequency PWM architecture that can be programmed to switch from 200kHz to 2.4MHz by using a resistor tied from the RT pin to ground. Table 2 provides a list of RT resistor values and their resultant frequencies. Table 2. Switching Frequency vs RT Value SWITCHING FREQUENCY (MHz) RT VALUE (kΩ) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 187 121 88.7 68.1 56.2 46.4 40.2 34 29.4 23.7 19.1 16.2 13.3 11.5 9.76 8.66 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. Operating Frequency Tradeoffs Ceramic capacitors are also piezoelectric. In Burst Mode operation, the LTM8022’s switching frequency depends on the load current, and can excite a ceramic capacitor at audio frequencies, generating audible noise. Since the LTM8022 operates at a lower current limit during Burst 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 LTM8022 is flexible enough to accommodate a wide range 8022fb 9 LTM8022 APPLICATIONS INFORMATION 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 LTM8022 if the output is overloaded or short-circuited. A frequency that is too low can result in a final design that has too much output ripple or too large of an output cap. maximum voltage at the BIAS pin is less than 16V and the sum of VIN+ BIAS is less than 56V. If BIAS power is applied from a remote or noisy voltage source, it may be necessary to apply a decoupling capacitor locally to the LTM8022. The maximum frequency and corresponding RT value at which the LTM8022 should be allowed to switch is given in Table 1 in the RT(MIN) and fMAX columns, while the recommended frequency and RT value over the given input range is given in the RT(OPTIMAL) and fOPTIMAL columns. The LTM8022 is a step-down converter, so a minimum amount of headroom is required to keep the output in regulation. For most applications at full load, the input needs to be at least 1.5V above the desired output. In addition, the input voltage required to turn on depends upon how the RUN/SS pin is tied. As shown in Figure 1, it takes more input voltage to turn on if RUN/SS is tied to VIN than if the turn-on is controlled by raising RUN/SS when VIN is in the required operating range. This is shown in Figure 1. There are additional conditions that must be satisfied if the synchronization function is used. Please refer to the Synchronization section for details. Burst Mode Operation Minimum Input Voltage 6.0 Burst Mode operation is enabled by tying SYNC to GND. To disable Burst Mode operation, tie SYNC to a stable voltage source above 0.7V. Do not leave this pin floating. BIAS Pin Considerations The BIAS pin is used to provide drive power for the internal power switching stage and operate internal circuitry. For proper operation, it must be powered by at least 2.4V. If the output voltage is programmed to be 2.4V or higher, simply tie BIAS to AUX, which is internally tied to VOUT . If VOUT is less than 2.4V, BIAS can be tied to VIN or some other voltage source. In all cases, ensure that the VOUT = 3.3V TA = 25°C f = 650kHz INPUT VOLTAGE (V) 5.5 5.0 TO START 4.5 RUN/SS ENABLED 4.0 TO RUN 3.5 3.0 0 200 400 600 800 LOAD CURRENT (mA) 1000 8022 F01a 7.5 VOUT = 5V TA = 25°C f = 650kHz 7.0 INPUT VOLTAGE (V) To enhance efficiency at light loads, the LTM8022 automatically switches to Burst Mode operation which keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current. During Burst Mode operation, the LTM8022 delivers single cycle bursts of current to the output capacitor followed by sleep periods where the output power is delivered to the load by the output capacitor. In addition, VIN and BIAS quiescent currents are reduced to typically 20μA and 50μA, respectively, during the sleep time. As the load current decreases towards a no load condition, the percentage of time that the LTM8022 operates in sleep mode increases and the average input current is greatly reduced, resulting in higher efficiency. 6.5 TO START RUN/SS ENABLE 6.0 5.5 TO RUN 5.0 0 200 600 400 800 LOAD CURRENT (mA) 1000 8022 F01b Figure 1. The LTM8022 Needs More Voltage to Start Than to Run 8022fb 10 LTM8022 APPLICATIONS INFORMATION Load Sharing Two or more LTM8022’s may be paralleled to produce higher currents. To do this, tie the VIN, VOuT and SHARE pins of all the paralleled LTM8022’s together. Synchronize the LTM8022s to avoid beat frequencies if required. To ensure that paralleled modules start up together, the RUN/SS pins may be tied together, as well. If the RUN/SS pins are not tied together, make sure that the same valued soft-start capacitors are used for each module. An example of two LTM8022 modules configured for load sharing is given in the Typical Applications section. Soft-Start The RUN/SS pin can be used to soft-start the LTM8022, reducing the maximum input current during start-up. The RUN/SS pin is driven through an external RC filter to create a voltage ramp at this pin. Figure 2 shows the start-up and shutdown waveforms with the soft-start circuit. By choosing an appropriate RC time constant, the peak start-up current can be reduced to the current that is required to regulate the output, with no overshoot. Choose the value of the resistor so that it can supply at least 20μA when the RUN/SS pin reaches 2.5V. Synchronization The internal oscillator of the LTM8022 can be synchronized by applying an external 250kHz to 2MHz clock signal to the SYNC pin. The resistor tied from the RT pin to ground should be chosen such that the LTM8022 would free run 20% lower than the intended synchronization frequency (see Frequency Selection section). When the LTM8022 is synchronized to an external clock source, Burst Mode operation is disabled. The part will skip power switching cycles as necessary to maintain regulation. Ensure that the SYNC pin is not left floating. Tie it to GND if not used. Shorted Input Protection Care needs to be taken in systems where the output will be held high when the input to the LTM8022 is absent. This may occur in battery charging applications, or in battery backup systems where a battery or some other supply is diode ORed with the LTM8022’s output. If the VIN pin is allowed to float, and the RUN/SS pin is held high (either by a logic signal or because it is tied to VIN), then the LTM8022’s internal circuitry will pull its quiescent current through its internal power switch. This is fine if your system can tolerate a few milliamps in this state. If you ground the RUN/SS pin, the SW pin current will drop to essentially zero. However, if the VIN pin is grounded while the output is held high, then parasitic diodes inside the LTM8022 can pull large currents from the output through the VIN pin. Figure 3 shows a circuit that will run only when the input voltage is present and that protects against a shorted or reversed input. VIN VOUT VIN VOUT AUX LTM8022 RUN BIAS IL 0.5A/DIV 15k RUN/SS RUN/SS VRUN/SS 2V/DIV GND PG RT GND SYNC ADJ 0.22μF VOUT 2V/DIV 2ms/DIV Figure 2. To Soft-Start the LTM8022, Add a Resistor and Capacitor to the RUN/SS Pin 8022 F02 8022 F03 Figure 3. The Input Diode Prevents a Shorted Input from Discharging a Back-Up Battery Tied to the Output. It Also Protects the Circuit From a Reversed Input. The LTM8022 Runs Only When the Input is Present 8022fb 11 LTM8022 APPLICATIONS INFORMATION PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8022. The LTM8022 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 4 for a suggested layout. Ensure that the grounding and heatsinking are acceptable. A few rules to keep in mind are: 1. Place the RADJ and RT resistors as close to their respective pins as possible. 3. Place the COUT capacitor as close as possible to the VOUT and GND connection of the LTM8022. 4. Place the CIN and COUT capacitors such that their ground current flow directly adjacent or underneath the LTM8022. 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 LTM8022. 6. Use vias to connect the GND copper area to the boards internal ground plane. Liberally distribute these GND vias to provide both a good ground connection and thermal path to the internal planes of the printed circuit board. 2. Place the CIN capacitor as close as possible to the VIN and GND connection of the LTM8022. GND PLANE RT RADJ SHARE SYNC PG RUN/SS AUX BIAS LTM8022 VOUT PLANE CIN VIN PLANE 8022 F04 COUT Figure 4. Layout Showing Suggested External Components, GND Plane and Thermal Vias 8022fb 12 LTM8022 APPLICATIONS INFORMATION Hot-Plugging Safely Thermal Considerations The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of LTM8022. However, these capacitors can cause problems if the LTM8022 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. In this case, the voltage at the VIN pin of the LTM8022 can ring to twice the nominal input voltage, possibly exceeding the LTM8022’s rating and damaging the part. If the input supply is poorly controlled or the user will be plugging the LTM8022 into an energized supply, the input network should be designed to prevent this overshoot. Figure 5 shows the waveforms that result when an LTM8022 circuit is connected to a 24V supply through six feet of 24-gauge twisted pair. The first plot is the response with a 2.2μF ceramic capacitor at the input. The input voltage rings as high as 35V and the input current peaks at 20A. One method of damping the tank circuit is to add another capacitor with a series resistor to the circuit. In Figure 5b an aluminum electrolytic capacitor has been added. This capacitor’s 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 likely to be the largest component in the circuit. An alternative solution is shown in Figure 5c. A 0.7Ω resistor is added in series with the input to eliminate the voltage overshoot (it also reduces the peak input current). A 0.1μF capacitor improves high frequency filtering. This solution is smaller and less expensive than the electrolytic capacitor. For high input voltages its impact on efficiency is minor, reducing efficiency less than one half percent for a 5V output at full load operating from 24V. The LTM8022 output current may need to be derated if it is required to operate in a high ambient temperature or deliver a large amount of power. The amount of current derating is dependent upon the input voltage, output power and ambient temperature. The derating curves in the Typical Performance Characteristics section can be used as a guide. These curves were generated by an LTM8022 mounted to a 33cm2 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. The die temperature of the LTM8022 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 LTM8022. To estimate the junction temperature, approximate the power dissipation within the LTM8022 by applying the typical efficiency stated in this datasheet to the desired output power, or, if you have an actual module, by taking a power measurement. Then calculate the temperature rise of the LTM8022 junction above the surface of the printed circuit board by multiplying the module’s power dissipation by the thermal resistance. The actual thermal resistance of the LTM8022 to the printed circuit board depends upon the layout of the circuit board, but the thermal resistance given on page 2, which is based upon a 33cm2 4-layer FR4 PC board, can be used a guide. Finally, be aware that at high ambient temperatures the internal Schottky diode will have significant leakage current (see Typical Performance Characteristics) increasing the quiescent current of the LTM8022. 8022fb 13 LTM8022 APPLICATIONS INFORMATION CLOSING SWITCH SIMULATES HOT PLUG IIN DANGER VIN LTM8022 VIN 20V/DIV + RINGING VIN MAY EXCEED ABSOLUTE MAXIMUM RATING 4.7μF LOW IMPEDANCE ENERGIZED 24V SUPPLY STRAY INDUCTANCE DUE TO 6 FEET (2 METERS) OF TWISTED PAIR IIN 10A/DIV 20μs/DIV (5a) LTM8022 + 22μF 35V AI.EI. + VIN 20V/DIV 4.7μF IIN 10A/DIV (5b) 0.7Ω LTM8022 20μs/DIV VIN 20V/DIV + 0.1μF 4.7μF IIN 10A/DIV 20μs/DIV 8022 F05 (5c) Figure 5. A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation When the LTM8022 is Connected to a Live Supply 8022fb 14 LTM8022 TYPICAL APPLICATIONS 0.82V Step-Down Converter VIN* 3.6V TO 15V VIN VOUT LTM8022 2.2μF BIAS 200μF VOUT 0.82V 1A AUX RUN/SS PG SHARE RT GND SYNC ADJ 69.8k 13M 8022 TA02 *RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION FOR START-UP DETAILS 1.8V Step-Down Converter VIN* 3.6V TO 15V VIN VOUT LTM8022 2.2μF BIAS 68μF VOUT 1.8V 1A AUX RUN/SS PG SHARE RT 39.2k GND SYNC ADJ 383k 8022 TA03 *RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION FOR START-UP DETAILS 8022fb 15 LTM8022 TYPICAL APPLICATIONS 2.5V Step-Down Converter VIN* 3.8V TO 36V VIN VOUT LTM8022 2.2μF 3.3V 47μF RUN/SS AUX SHARE PG VOUT 2.5V 1A BIAS RT GND SYNC ADJ 59k 226k 8022 TA04 *RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION FOR START-UP DETAILS –5V at 1A Positive-to-Negative Converter –5V at 1A Positive-to-Negative Converter Load Current vs Input Voltage 1200 IN OUT LTM8022 AUX SHARE BIAS 2.2μF PG RT 29.4k 1000 RUN/SS 10μF OPTIONAL SCHOTTKY CLAMP GND SYNC ADJ 800 600 400 200 93.1k 8022 TA05 *RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION FOR START-UP DETAILS LOAD CURRENT (mA) VIN* 7V TO 31V VOUT –5V 0 0 10 20 30 INPUT VOLTAGE (V) 40 8022 TA05b 8022fb 16 LTM8022 TYPICAL APPLICATIONS Two LTM8022’s in Parallel, 3.3V at 1.8A VIN* 5.5V TO 36V IN VOUT 3.3V 1.8A OUT LTM8022 RUN/SS AUX SHARE BIAS PG 2.2μF RT GND SYNC ADJ 43.2k 78.7k OPTIONAL SYNC IN OUT LTM8022 RUN/SS AUX SHARE BIAS 10μF PG 2.2μF RT GND SYNC ADJ 43.2k 8022 TA06 *RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION FOR START-UP DETAILS NOTE: SYNCRONIZE THE TWO MODULES TO AVOID BEAT FREQUENCIES IF REQUIRED. OTHERWISE, TIE EACH SYNC TO GND 8022fb 17 0.000 3.810 2.540 1.270 0.3175 0.3175 1.270 2.540 0.000 SUGGESTED PCB LAYOUT TOP VIEW 1.905 PACKAGE TOP VIEW 0.635 3.175 aaa Z 3.810 4 0.635 0.9525 0.635 0.3175 PAD 1 CORNER 1.905 X 9.00 BSC Y aaa Z 2.45 – 2.55 DETAIL A MOLD CAP Z 0.27 – 0.37 SUBSTRATE 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 A MARKED FEATURE 4 SYMBOL TOLERANCE 0.15 aaa 0.10 bbb 6. THE TOTAL NUMBER OF PADS: 50 5. PRIMARY DATUM -Z- IS SEATING PLANE LAND DESIGNATION PER JESD MO-222, SPP-010 AND SPP-020 3 2. ALL DIMENSIONS ARE IN MILLIMETERS TRAY PIN 1 BEVEL 3 PADS SEE NOTES 1.27 BSC 0.605 – 0.665 7.62 BSC NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 DETAIL A PACKAGE SIDE VIEW 2.72 – 2.92 bbb Z 18 4.445 11.25 BSC H G E D C B A LGA 50 0507 REV B PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX μModule PACKAGE BOTTOM VIEW F 8.89 BSC 0.605 – 0.665 1 2 3 4 5 6 7 C(0.30) PAD 1 LTM8022 PACKAGE DESCRIPTION LGA Package 50-Lead (11.25mm × 9.00mm × 2.82mm) (Reference LTC DWG # 05-08-1804 Rev B) 8022fb 4.445 3.175 LTM8022 PACKAGE DESCRIPTION Table 3. LTM8022 Pinout (Sorted by Pin Number) PIN SIGNAL DESCRIPTION PIN SIGNAL DESCRIPTION A1 VOUT D5 GND A2 VOUT D6 GND A3 VOUT D7 GND A4 VOUT E1 GND A5 GND E2 GND A6 GND E3 GND A7 GND E4 GND B1 VOUT E5 GND B2 VOUT E6 GND B3 VOUT E7 GND B4 VOUT F5 AUX B5 GND F6 GND B6 GND F7 SHARE B7 GND G1 VIN C1 VOUT G2 VIN C2 VOUT G3 VIN C3 VOUT G5 BIAS C4 VOUT G6 SYNC C5 GND G7 RT C6 GND H1 VIN C7 GND H2 VIN D1 GND H3 VIN D2 GND H5 RUN/SS D3 GND H6 PG D4 GND H7 ADJ 8022fb Information f μrnished by Linear Technology Corporation is believed to be acc μrate and reliable. However, no responsibility is ass μmed for its μse. Linear Technology Corporation makes no representation that the interconnection of its circ μits as described herein will not infringe on existing patent rights. 19 LTM8022 TYPICAL APPLICATION 3.3V Step Down Converter VIN* 4.75V TO 36V IN OUT LTM8022 RUN/SS AUX SHARE BIAS 2.2μF 22μF VOUT 3.3V 1A PG RT GND SYNC ADJ 42.2k 154k 8022 TA07 *RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION FOR START-UP DETAILS RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTM4600/LTM4602 10A and 6A DC/DC μModule Pin Compatible, 4.5V ≤ VIN ≤ 28V LTM4601/LTM4603 12A and 6A DC/DC μModule Pin Compatible; Remote Sensing; PLL, Tracking and Margining, 4.5V ≤ VIN ≤ 28V LTM4604/LTM4608 4A, 8A Low Voltage DC/DC μModule 2.375V ≤ VIN ≤ 5.5V, 9mm × 15mm × 2.3mm (LTM4604), 9mm × 15mm × 2.5mm (LTM4608) LTM4605/LTM4607 Buck-Boost DC/DC μModule Up to 160W, External Inductor; High Efficiency (Up to 98%), 15mm × 15mm × 2.8mm LGA LTM8020 200mA, 36V DC/DC μModule 4V ≤ VIN ≤ 36V, 1.25V ≤ VOUT ≤ 5V, 6.25mm × 6.25mm × 2.32mm LGA LTM8023 2A, 36V DC/DC μModule 3.6V ≤ VIN ≤ 36V, 0.8V ≤ VOUT ≤ 10V, 11.25mm × 9mm × 2.82mm LGA, Pin Compatible with LTM8022 8022fb 20 Linear Technology Corporation LT 1008 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008