LTM8001 36VIN, 5A µModule Regulator with 5-Output Configurable LDO Array FEATURES n n n n DESCRIPTION Complete Step-Down Switch Mode Power Supply with Configurable Array of Five LDOs Step-Down Switching Power Supply – Adjustable 10% Accurate Output Current Limit –Constant-Current, Constant-Voltage Operation – Wide Input Voltage Range: 6V to 36V – 1.2V to 24V Output Voltage Configurable Output LDO Array – Five 1.1A Parallelable Outputs – Outputs Adjustable from 0V to 24V – Low Output Noise: 90μVRMS (10Hz to 1MHz) 15mm × 15mm × 3.42mm Surface Mount BGA Package The LTM®8001 is a 36VIN, 5A step-down μModule® regulator with a 5-output configurable LDO array. Operating over an input voltage range of 6V to 36V, the LTM8001 buck regulator supports an output voltage range of 1.2V to 24V. Following the buck regulator is an array of five 1.1A linear regulators whose outputs may be connected in parallel to accommodate a wide variety of load combinations. Three of these LDOs are tied to the output of the buck regulator, while the other two are tied together to an undedicated input. The low profile package (3.42mm) enables utilization of unused space on the bottom of PC boards for high density point of load regulation. The LTM8001 is packaged in a thermally enhanced, compact (15mm × 15mm) and low profile (3.42mm) overmolded ball grid array (BGA) package suitable for automated assembly by standard surface mount equipment. The LTM8001 is RoHS compliant. APPLICATIONS n n n FPGA, DSP, ASIC and Microprocessor Supplies Servers and Storage Devices RF Transceivers 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. TYPICAL APPLICATION 5A Output DC/DC µModule Converter VIN45 VIN 6V TO 36V 10µF 3.3V VIN0 510k RUN BIAS123 BIAS45 LTM8001 COMP SS VREF ILIM SYNC GND 1.8V 1A 1.2V 1A VOUT0 LDO 1 VOUT1 SET1 1.1V 1.5A VOUT2 STEP-DOWN LDO 2 SET2 SWITCHING V REGULATOR LDO 3 OUT3 SET3 LDO 4 VOUT5 FBO LDO 5 SET5 RT 118k 19.6k 0.9V 1.5A VOUT4 SET4 4.7µF 4.7µF 2.2µF 45.3k 54.9k 121k 350kHz 470µF + 100µF 8001 TA01 8001f For more information www.linear.com/8001 1 LTM8001 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VIN0............................................................................40V VIN45, BIAS45............................................................25V BIAS123.....................................................................25V FB0, RT, COMP, ILIM, VREF..........................................3V VOUT0-5......................................................................25V RUN, SYNC, SS............................................................6V SET1-5 (Relative to VOUT1-5, Respectively).............±0.3V Current Into SET1-5.............................................. ±10mA Current Into RUN Pin.............................................100µA Maximum Junction Temperature (Notes 2, 3)........ 125°C Peak Body Reflow Temperature............................. 245°C Storage Temperature.............................. –55°C to 125°C TOP VIEW VOUT4 SET4 VOUT3 SET3 SET2 VOUT2 11 VOUT5 10 SET5 9 BIAS123 8 VOUT1 VREF BIAS45 SYNC 7 VIN45 BANK 3 6 GND ILIM RT COMP BANK 2 5 VOUT0 BANK 4 4 SET1 SS FBO RUN 3 VIN0 BANK 1 2 1 A B C D E F G H J K L BGA PACKAGE 121 PADS (15mm × 15mm × 3.42mm) TJMAX = 125°C, θJA = 16.1°C/W, θJCbottom = 5.99°C/W, θJCtop = 13.4°C/W, θJB = 4.98°C/W θ VALUES DETERMINED PER JEDEC 51-9, 51-12 WEIGHT = 1.8 GRAMS ORDER INFORMATION LEAD FREE FINISH TRAY PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE (Note 3) LTM8001EY#PBF LTM8001EY#PBF LTM8001Y 121-Lead (15mm × 15mm × 3.42mm) BGA –40°C to 125°C LTM8001IY#PBF LTM8001IY#PBF LTM8001Y 121-Lead (15mm × 15mm × 3.42mm) BGA –40°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/ 8001f 2 For more information www.linear.com/8001 LTM8001 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. RUN = 3V unless otherwise noted (Note 3). PARAMETER CONDITIONS MIN TYP MAX UNITS Buck Regulator Minimum VIN0 Input Voltage 6 l VOUT0 Output DC Voltage 0A < IOUT ≤ 3A, RFB0 Open 0A < IOUT ≤ 3A; RFB0 = 536Ω VOUT0 Output DC Current 6V < VIN0 < 36V, VOUT = 3.3V Quiescent Current Into VIN0 RUN = 0V No Load 0.1 26 1.2 24 0 V V V 5 A 1 40 µA mA VOUT0 Line Regulation 6V < VIN0 < 36V, IOUT = 4.5A ±0.5 % VOUT0 Load Regulation VIN0 = 24V, 0A < IOUT < 4.5A ±1.2 % VOUT0 RMS Voltage Ripple VIN0 = 24V, IOUT = 4.5A 10 mV Switching Frequency RT = 39.2k RT = 200k 1000 200 kHz kHz Voltage at FB0 Pin l 1.15 Internal FBO Resistor RUN Pin Current 1.19 1.21 10 RUN = 1.45V V kΩ 5.5 µA RUN Threshold Voltage (Falling) 1.49 1.61 V RUN Threshold Voltage (Rising) 1.63 1.75 V ILIM Control Range 0 ILIM Pin Current 1.5 100 ILIM Current Limit Accuracy ILIM = 1.5V ILIM = 0.75V 5.1 2.5 VREF Voltage 0.5mA Load 1.9 SYNC Input Low Threshold fSYNC = 500kHz 0.8 SYNC Input High Threshold fSYNC = 500kHz SYNC Input Current SYNC = 0V SYNC = 2V SS Pin Current 2 V nA 6.4 3.4 A A 2.1 V 11 µA V –0.1 1.2 V 0.1 µA µA 10.15 10.20 µA µA 4 6 mV mV 11 nA LDO Array SET1-5 Pin Current VOUTx – SETx Offset Voltage BIAS123 = BIAS45 = 2V, SETx = 0V, IOUT1-5 = 1mA l 9.85 9.80 l –4 –6.5 BIAS123 = BIAS45 = 2V, SETx = 0V, IOUT1-5 = 1mA Line Regulation for SET Current 1V < VOUT0 = VIN45 < 22V, IOUTx = 1mA (Note 4) Line Regulation for VOUT1-5 1V < VOUT0 = VIN45 < 22V, IOUTx = 1mA (Note 4) 10 10 l 0.25 mV Load Regulation for SETx Current IOUT1-5 = 1mA to 1.1A 1 nA Load Regulation for VOUT1-5 IOUT1-5 = 1mA to 1.1A l 34 52 mV mV Minimum Load Current for VOUT1-5 (Note 4) VOUT0 = VIN45 = BIAS123 = BIAS45 = 10V VOUT0 = VIN45 = BIAS123 = BIAS45 = 22V l l 500 1 µA mA BIAS123, BIAS45 Dropout Voltage IOUT1-5 = 100mA IOUT1-5 = 1.1A l 1.6 V V VOUT0 to VOUT1-3 and VIN45 to VOUT4-5 Dropout IOUT1-5 = 100mA Voltage IOUT1-5 = 1.1A l 500 mV mV 1.2 100 8001f For more information www.linear.com/8001 3 LTM8001 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. RUN = 3V unless otherwise noted (Note 3). PARAMETER CONDITIONS Maximum VOUT0 to VOUT1-3 and VIN45 to VOUT4-5 Differential Voltage (Note 5) IOUT1-5 = 750mA IOUT1-5 = 310mA IOUT1-5 = 125mA BIAS123, BIAS45 Pin Current IOUT1-5 = 100mA IOUT1-5 = 1.1A MIN TYP MAX l UNITS 10 15 22 V V V 6 30 mA mA VOUT1-5 Current Limit (Note 5) VOUT1-5 = 0V 1.3 A VOUT1-5 RMS Output Noise VOUT1-5 = 1V, IOUT1-5 = 1A, 100Hz to 1MHz 90 µVRMS LTM8001I is guaranteed to meet specifications over the full –40°C to 125°C internal operating temperature range. Note that the maximum internal temperature is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. Note 4: No minimum load is required if the respective linear regulator is off, such as when VOUT0 = 0V, VIN45 = 0V, BIAS123 = 0V or BIAS45 = 0V. Note 5: The current limit may decrease to zero at input-to-output differential voltages greater than 22V. Operation at voltages for VOUT0, VIN45, BIAS123 and BIAS45 is allowed up to a maximum of 36V as long as the difference between the linear regulator input and output voltage is below the specified differential voltage. Line and load regulation specifications are not applicable when the device is in current limit. 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. Junction temperature will exceed 125°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 3: The LTM8001E is guaranteed to meet performance specifications from 0°C to 125°C internal. Specifications over the full –40°C to 125°C internal operating temperature range are assured by design, characterization and correlation with statistical process controls. The TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted. Configured per Table 1, where applicable.) Efficiency vs Output Current, VOUT0 = 3.3V Efficiency vs Output Current, VOUT0 = 5V 95 100 85 90 95 80 85 90 75 70 80 75 70 65 VINO = 12V VINO = 24V VINO = 36V 60 55 EFFICIENCY (%) 90 EFFICIENCY (%) EFFICIENCY (%) Efficiency vs Output Current, VOUT0 = 2.5V 0 1 2 3 4 VOUT0 CURRENT (A) 60 0 1 2 3 5 4 VINO = 12V VINO = 24V VINO = 36V 70 VOUT0 CURRENT (A) 8001 G01 80 75 VINO = 12V VINO = 24V VINO = 36V 65 5 85 65 0 1 2 3 4 5 VOUT0 CURRENT (A) 8001 G02 8001 G03 8001f 4 For more information www.linear.com/8001 LTM8001 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted. Configured per Table 1, where applicable.) Efficiency vs Output Current, VOUT0 = 12V 100 95 95 90 90 85 80 VINO = 12V VINO = 24V VINO = 36V 75 70 0 1 2 3 100 95 85 80 70 VINO = 24V VINO = 36V 0 1 2 3 1.5 100 85 1.8 VINO = 12V VINO = 24V VINO = 36V 4 1.4 0.9 0.6 0 5 0 1 3 VOUT0 CURRENT (A) 2 4 0.5 5 8001 G10 0 1 3 2 VOUT0 CURRENT (A) 8001 G09 2.5 INPUT CURRENT (A) 3.0 2.5 2.0 1.5 0 2.0 1.5 1.0 0.5 0 1 2 3 VOUT0 CURRENT (A) 5 4 3.0 0.5 4 0.6 Input Current vs Output Current, VOUT0 = 12V 1.0 3 VOUT0 CURRENT (A) 0.8 0 5 VINO = 12V VINO = 24V VINO = 36V 3.5 INPUT CURRENT (A) INPUT CURRENT (A) 4.0 1.0 2 1.0 Input Current vs Output Current, VOUT0 = 8V VINO = 12V VINO = 24V VINO = 36V 1 1.2 8001 G08 Input Current vs Output Current, VOUT0 = 5V 0 5 0.2 1.5 0 4 0.4 8001 G07 2.0 3 2 VOUT0 CURRENT (A) VINO = 12V VINO = 24V VINO = 36V 1.6 0.3 VINO = 28V VINO = 36V 3 VOUT0 CURRENT (A) 1 Input Current vs Output Current, VOUT0 = 3.3V INPUT CURRENT (A) INPUT CURRENT (A) EFFICIENCY (%) 90 2 0 8001 G06 Input Current vs Output Current, VOUT0 = 2.5V 1.2 95 1 VINO = 28V VINO = 36V 8001 G05 Efficiency vs Output Current, VOUT0 = 24V 2.5 75 5 4 8001 G04 0 85 VOUT0 CURRENT (A) VOUT0 CURRENT (A) 80 90 80 75 5 4 Efficiency vs Output Current, VOUT0 = 18V EFFICIENCY (%) 100 EFFICIENCY (%) EFFICIENCY (%) Efficiency vs Output Current, VOUT0 = 8V 4 5 0 VINO = 24V VINO = 36V 0 1 2 3 4 5 VOUT0 CURRENT (A) 8001 G11 8001 G12 8001f For more information www.linear.com/8001 5 LTM8001 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted. Configured per Table 1, where applicable.) Input Current vs Output Current, VOUT0 = 24V 4.0 5.0 3.5 4.5 7 2.0 1.5 1.0 MINIMUM VIN0 VOLTAGE (V) 2.5 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 VINO = 28V VINO = 36V 0 1 2 3 VOUT0 CURRENT (A) 4 VINO = 28V VINO = 36V 0.5 0 5 0 1 3 VOUT0 CURRENT (A) 2 4 2 3 9.75 0 1 VOUT0 CURRENT (A) 2 3 13.85 13.80 13.75 13.70 13.65 25.95 25.90 25.85 25.75 19.66 19.65 25.70 25.65 4 5 VOUT0 CURRENT (A) 8001 G19 25.55 2.5 2.0 1.5 1.0 0.5 25.60 3 5 4 3.0 26.00 25.80 19.67 3 3.5 OUTPUT VOLTAGE (V) MINIMUM VIN0 VOLTAGE (V) 19.70 2 2 Output Voltage vs Output Current, VOUT0 = 2.5V 26.05 1 1 8001 G18 26.10 0 0 VOUT0 CURRENT (A) Minimum VIN0 vs Output Current, VOUT0 = 24V 19.71 5 4 8001 G17 Minimum VIN0 vs Output Current, VOUT0 = 18V MINIMUM VIN0 VOLTAGE (V) 5 4 8001 G16 19.68 3 13.90 VOUT0 CURRENT (A) 19.69 2 13.95 9.80 9.70 5 4 1 Minimum VIN0 vs Output Current, VOUT0 = 12V MINIMUM VIN0 VOLTAGE (V) MINIMUM VIN0 VOLTAGE (V) MINIMUM VIN0 VOLTAGE (V) 6.70 0 8001 G1 9.85 6.75 19.64 4 5 Minimum VIN0 vs Output Current, VOUT0 = 8V 6.80 1 5 8001 G14 Minimum VIN0 vs Output Current, VOUT0 = 5V 0 6 VOUT0 CURRENT (A) 8001 G13 6.65 Minimum VIN0 vs Output Current, VOUT0 = 3.3V and Below 4.0 3.0 INPUT CURRENT (A) INPUT CURRENT (A) Input Current vs Output Current, VOUT0 = 18V 0 1 3 VOUT0 CURRENT (A) 2 5 4 0 –10 –5 0 5 10 LOAD CURRENT (A) 8001 G20 8001 G21 8001f 6 For more information www.linear.com/8001 LTM8001 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted. Configured per Table 1, where applicable.) 600 4 500 2 0 –2 –4 0 0.25 1 0.75 0.5 ILIM VOLTAGE (V) 1.25 0 12 18 24 VIN0 VOLTAGE (V) 6 30 0 36 0 1 2 3 VOUT0 CURRENT (A) 5 4 Temperature Rise vs VOUT0 Current, Buck Regulator, VOUT0 = 5V Temperature Rise vs VOUT0 Current, Buck Regulator, VOUT0 = 8V 70 80 70 20 12VIN 24VIN 36VIN 0 1 2 3 VOUT0 CURRENT (A) 50 40 30 20 12VIN 24VIN 36VIN 10 0 5 4 TEMPERATURE RISE (°C) 60 TEMPERATURE RISE (°C) TEMPERATURE RISE (°C) 12VIN 24VIN 36VIN 10 Temperature Rise vs VOUT0 Current, Buck Regulator, VOUT0 = 3.3V 10 0 1 2 3 50 40 30 20 12VIN 24VIN 36VIN 10 0 5 4 60 0 1 VOUT0 CURRENT (A) 2 3 VOUT0 CURRENT (A) 4 5 8001 G25 8001 G26 8001 G27 Temperature Rise vs VOUT0 Current, Buck Regulator, VOUT0 = 12V Temperature Rise vs VOUT0 Current, Buck Regulator, VOUT0 = 18V Temperature Rise vs VOUT0 Current, Buck Regulator, VOUT0 = 24V 120 90 100 90 100 80 TEMPERATURE RISE (°C) TEMPERATURE RISE (°C) 20 8001 G24 30 70 60 50 40 30 20 0 1 3 VOUT0 CURRENT (A) 2 4 80 60 40 20 24VIN 36VIN 10 0 200 30 8001 G23 40 100 300 40 8001 G22 50 0 400 0 1.5 Temperature Rise vs VOUT0 Current, Buck Regulator, VOUT0 = 2.5V 50 TEMPERATURE RISE (°C) 60 60 100 –6 –8 VIN0 Input Current vs Voltage, VOUT0 Shorted TEMPERATURE RISE (°C) 6 VIN0 INPUT CURRENT (mA) MAXIMUM CURRENT (A) ILIM Voltage vs Maximum IOUT0 Output Current 5 8001 G28 0 28VIN 36VIN 0 1 2 3 VOUT0 CURRENT (A) 70 36VIN 60 50 40 30 20 10 5 4 80 8001 G29 0 0 1 3 2 VOUT0 CURRENT (A) 4 5 8001 G30 8001f For more information www.linear.com/8001 7 LTM8001 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted. Configured per Table 1, where applicable.) LDO VBIAS-to-Output Dropout Voltage vs Output Current 350 300 250 200 150 100 50 0 0 200 400 800 600 OUTPUT CURRENT (mA) 1.52 1600 1.50 1400 1.48 1.46 1.44 1.42 1.40 1.38 0 200 400 800 600 OUTPUT CURRENT (mA) 8001 G31 800 600 400 0 1000 0 20 10 30 INPUT-TO-OUTPUT DIFFERENTIAL (V) 120 LDO INPUT-TO-OUTPUT DIFFERENTIAL VOLTAGE 80 0.5V 1.6V 2.4V 4V 7V 9.5V 11.9V 60 40 20 0 500 1000 LDO OUTPUT CURRENT (mA) 100 TEMPERATURE RISE (°C) 100 LDO INPUT-TO-OUTPUT DIFFERENTIAL VOLTAGE 80 0.5V 0.9V 2V 4V 7V 8.7V 11.9V 60 40 20 0 1500 0 1 2 3 4 TOTAL LDO OUTPUT CURRENT (A) 8001 G34 100 90 90 80 80 RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) LDO Input Voltage Ripple Rejection (VOUT4 = 2.5V, VBIAS45 = 4.5V, VIN45 = 3.5V) 100 70 60 50 40 30 20 5 8001 G35 LDO Input Voltage Ripple Rejection (VOUT4 = 2.5V, VIN45 = VBIAS45 = 4.5V) 70 60 50 40 30 20 ILOAD = 100mA ILOAD = 1.1A 10 0 40 8001 G33 LDO Temperature Rise vs LDO Output Current (VIN = 24V, VOUT0 = 12V, 5 LDOs in Parallel) 120 TEMPERATURE RISE (°C) 1000 8001 G32 LDO Temperature Rise vs LDO Output Current (VIN = 24V, VOUT0 = 12V, 1 LDO Powered) 0 1200 200 1.36 1.34 1000 LDO Current Limit vs Input-toOutput Differential Voltage LDO CURRENT LIMIT (mA) 400 BIAS-TO-OUTPUT DROPOUT VOLTAGE (V) INPUT-TO-OUTPUT DROPOUT VOLTAGE (mV) LDO Input-to-Output Dropout Voltage vs Output Current 10 102 103 104 FREQUENCY (Hz) ILOAD = 100mA ILOAD = 1.1A 10 105 106 0 10 102 8001 G36 103 104 FREQUENCY (Hz) 105 106 8001 G37 8001f 8 For more information www.linear.com/8001 LTM8001 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted. Configured per Table 1, where applicable.) LDO VBIAS Ripple Rejection (VOUT4 = 2.5V, VBIAS45 = 4.5V, VIN45 = 3.5V) LDO Output Ripple 100 90 RIPPLE REJECTION (dB) 80 1mV/DIV 70 60 50 40 30 20 ILOAD = 100mA ILOAD = 1.1A 10 0 10 102 103 104 FREQUENCY (Hz) 105 106 2µs/DIV VOUT = 1.2V AT 700mA COUT1 = 22µF CSET1 = 1nF VIN = 12V VOUT0 = 1.8V LOADED TO A TOTAL CURRENT OF 5A 100MHz BW 8001 G39 8001 G38 PIN FUNCTIONS VIN0 (Bank 1): The VIN0 bank supplies current to the LTM8001’s internal regulator and to the internal power switches. This pin must be locally bypassed with an external, low ESR capacitor; see Table 1 for recommended values. BIAS123 (Pin B8): This pin is the supply pin for the control circuitry of the LDOs connected to VOUT1-VOUT3. For the LDOs to regulate, this voltage must be more than 1.2V to 1.6V greater than the output voltage (see Dropout specifications). GND (Bank 2): Tie these GND pins to a local ground plane below the LTM8001 and the circuit components. In most applications, the bulk of the heat flow out of the LTM8001 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 (RFB0) to this net. SS (Pin K4): 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. VIN45 (Bank 3): Input to the LDOs connected to VOUT4 and VOUT5. It must be locally bypassed with a low ESR capacitor. VOUT0 (Bank 4): Switching Power Converter Output Pins. Apply the output filter capacitor and the output load between these pins and the GND pins. In most cases, an output capacitance made up of a combination of ceramic and electrolytic capacitors yields the optimal volumetric solution. BIAS45 (Pin A8): This pin is the supply pin for the control circuitry of the LDOs connected to VOUT4 and VOUT5. For the LDOs to regulate, this voltage must be more than 1.2V to 1.6V greater than the output voltage (see Dropout specifications). SYNC (Pin K7): 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% slower 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 Switching Frequency Synchronization section in Applications Information. VREF (Pin K8): Buffered 2V Reference Capable of 0.5mA Drive. RUN (Pin L4): The RUN pin acts as an enable pin and turns on the internal circuitry. The pin does not have any pull up or pull down, requiring a voltage bias for normal part operation. The RUN pin is internally clamped, so it may be pulled up to a voltage source that is higher than 8001f For more information www.linear.com/8001 9 LTM8001 PIN FUNCTIONS the absolute maximum voltage rating of 6V through a resistor, provided the pin current does not exceed 100µA. 20% lower than the SYNC pulse frequency. Do not leave this pin open. FB0 (Pin L5): The LTM8001 regulates its FB0 pin to 1.19V. Connect the adjust resistor from this pin to ground. The value of RFB0 is given by the equation: ILIM (Pin L8): The ILIM pin reduces the maximum regulated output current of the LTM8001. The maximum control voltage range is 1.5V. ILIM voltages above 1.5V have little or no effect. If this function is not used, tie this pin to VREF. RFBO = 11.9 VOUT – 1.19 where RFB0 is in kΩ. COMP (Pin L6): Compensation Pin. This pin is generally not used. The LTM8001 is internally compensated, but some rare situations may arise that require a modification to the control loop. This pin connects directly to the input PWM comparator of the LTM8001. In most cases, no adjustment is necessary. If this function is not used, leave this pin open. RT (Pin L7): The RT pin is used to program the switching frequency of the LTM8001 by connecting a resistor from this pin to ground. The Applications Information section of the data sheet includes a table to determine the recommended resistance value and switching frequency. When using the SYNC function, set the frequency to be SET1, SET2, SET3, SET4, SET5 (Pins L9, H11, G11, D11, A9): These pins set the regulation point for each LDO. A fixed current of 10μA flows out of this pin through a single external resistor, which programs the output voltage of the device. Output voltage range is zero to the absolute maximum rated output voltage. The transient performance can be improved by adding a small capacitor from the SET pin to ground. VOUT1 (Pins L10, L11), VOUT2 (Pins J11, K11), VOUT3 (Pins E11, F11), VOUT4 (Pins B11, C11), VOUT5 (Pins A10, A11): These are the power outputs of the individual LDOs. There must be a minimum load current of 1mA or the output may not regulate. The internal LDOs are rated for positive voltages between their inputs and outputs. Avoid applications where the internal LDOs can experience a negative voltage, even during start-up and turn-off transients BLOCK DIAGRAM 2.2µH VIN0 0.2µF RSENSE VOUT0 10k 2.2µF VOUT1 1.1A LDO SET1 VOUT2 1.1A LDO SET2 VOUT3 RUN 1.1A LDO SET3 SS SYNC VREF CURRENT MODE CONTROLLER VIN0 VOUT4 INTERNAL REGULATOR 1.1A LDO SET4 VOUT5 ILIM 1.1A LDO COMP GND RT FB0 BIAS123 SET5 BIAS45 VIN45 8001 BD 8001f 10 For more information www.linear.com/8001 LTM8001 OPERATION The LTM8001 consists of two major parts: the first is a standalone nonisolated step-down switching DC/DC power converter that can deliver up to 5A of output current. The second part is an array of five parallelable 1.1A LDOs. The DC/DC converter 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 it is a step-down converter, make sure that the input voltage is high enough to support the desired output voltage and load current. The linear regulator array consists of five low drop-out regulators, of which three inputs are dedicated to the buck converter’s output (VOUT0) and two tie to an undedicated input (VIN45). Each individual linear regulator may be set to a unique voltage through its SET pin, or may be paralleled with other LDOs by tying their respective SET and VOUT pins together. can be used with a resistor between RUN and VIN0 to set hysteresis. Please refer to the UVLO and Shutdown section in the Applications Information for further details. During start-up, 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. The LTM8001 is equipped with thermal shutdown circuitry 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. Thus, 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 LTM8001 step-down switching converter utilizes fixed frequency, average current mode control to accurately regulate the output current. This results in a constantvoltage, constant-current output characteristic, making the LTM8001’s step-down regulator well suited for many supercapacitor and battery charging applications. As shown in the Typical Performance Characteristics, the current limit works in both directions. The control loop will regulate the current in the internal inductor. Once the VOUT0 output has reached the regulation voltage determined by the resistor from the FBO pin to ground, the voltage regulation loop will reduce the output current and maintain the output voltage. The ILIM input may be used to set the maximum allowable current output of the LTM8001. The analog control range of the ILIM pin is from 0V to 1.5V. If the ILIM pin is raised above 1.5V, there is little or no effect. The VOUT1-5 linear regulators are easy to use and have all the protection features expected in high performance regulators. Included are short-circuit protection and safe operating area protection, as well as thermal shutdown. These linear regulators are especially well suited to applications needing multiple rails. Their architecture allows their outputs to be adjusted down to zero volts. The output voltage is set by a single resistor, handling modern low voltage digital ICs as well as allowing easy parallel operation and simplified thermal management. The RUN pin functions as a precision enable for the stepdown switching converter connected to VOUT0. As the VOUT1-3 LDO inputs are tied to VOUT0, the RUN pin will also implicitly enable or disable these LDOs as well, unless some external power source is tied to VOUT0. Refer to the Applications Information section Shorted Input Protection if VOUT0 is forced above VIN0. 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 The linear regulators can be operated in two modes. One mode has the BIAS123 and BIAS45 pins connected to the linear regulator power input pins (VOUT0 and VIN45) which gives a limitation of about 1.6V dropout. In the other mode, the BIAS123 and BIAS45 pins can be tied to a voltage at least 1.6V above their highest respective outputs. The linear regulator power input (VOUT0 and VOUT45) can then be set to a lower voltage that meets the dropout requirement, minimizing the power dissipation. The switching frequency is determined by a resistor at the RT pin. The LTM8001 may also be synchronized to an external clock through the use of the SYNC pin. Please see the Switching Frequency Synchronization section in the Applications Information for further details. 8001f For more information www.linear.com/8001 11 LTM8001 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 VOUT0 output voltage. 2. Apply the recommended CIN0, COUT0, RFB0 and RT values. Note that ceramic and electrolytic capacitors are recommended. These are intended to work in concert to optimize performance and solution size; apply both capacitors. 3. Apply the set resistors for the VOUT1, VOUT2, VOUT3, VOUT4 and VOUT5 regulators. To set the voltage of each linear regulator, use the equation RSETX = VOUTX 10µA where the value of RSET is in Ohms. Note that there is no minimum positive output voltage for the regulator, but a minimum load current is required to maintain regulation regardless of output voltage, (please see Electrical Characteristics table). For true zero voltage output operation, this minimum load current must be returned to a negative supply voltage. If paralleling the linear regulators, set the output of each regulator to the same voltage by tying the SETx pins together and applying a single resistor. The value of the single set resistor is given by the equation: The maximum frequency (and attendant RT value) at which the LTM8001 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. 4. Apply the output capacitors for the VOUT1, VOUT2, VOUT3, VOUT4 and VOUT5 regulators. A minimum output capacitor of 2.2μF with an ESR of 0.5Ω or less is recommended to prevent oscillations. 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. 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 other factors. Please refer to the graphs in the Typical Performance Characteristics section for guidance. A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LTM8001. A ceramic input capacitor combined with trace or cable inductance forms a high Q (under damped) tank circuit. If the LTM8001 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. RSET = VOUT 10µA • n where n is the number of regulators paralleled. 8001f 12 For more information www.linear.com/8001 LTM8001 APPLICATIONS INFORMATION LTM8001 Table 1: Recommended Component Values and Configuration for VOUT0 (TA = 25°C) VIN0 VOUT0 6V to 36V 1.2V 6V to 36V 1.5V 6V to 36V CIN0 COUT0 (CERAMIC) COUT0 (ELECTROLYTIC) 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G RFB0 fOPTIMAL RT(OPTIMAL) fMAX RT(MIN) Open 200kHz 200k 250kHz 169k 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 38.3k 300kHz 140k 350kHz 118k 1.8V 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 19.6k 350kHz 118k 400kHz 102k 6V to 36V 2.5V 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 9.09k 450kHz 90.9k 525kHz 78.7k 6V to 36V 3.3V 7V to 36V 5V 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 5.62k 550kHz 75.0k 625kHz 64.9k 10µF, 50V, 1210 100µF, 6.3V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 3.09k 600kHz 68.1k 700kHz 57.6k 10V to 36V 8V 10µF, 50V, 1210 100µF, 10V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 1.74k 625kHz 64.9k 750kHz 53.6k 15V to 36V 12V 10µF, 50V, 1210 47µF, 16V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 1.10k 650kHz 61.9k 800kHz 49.9k 22V to 36V 18V 10µF, 50V, 1210 22µF, 25V, 1210 47µF, 20V, 45mΩ, OS-CON, 20SVPS47M 715Ω 675kHz 59.0k 900kHz 44.2k 28V to 36V 24V 4.7µF, 50V, 1210 10µF, 50V, 1206 47µF, 35V, 30mΩ, OS-CON, 35SVPC47M 523Ω 700kHz 57.6k 1MHz 39.2k 9V to 15V 1.2V 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G Open 200kHz 200k 525kHz 78.7k 9V to 15V 1.5V 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 38.3k 300kHz 140k 650kHz 61.9k 9V to 15V 1.8V 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 19.6k 350kHz 118k 800kHz 49.9k 9V to 15V 2.5V 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 9.09k 450kHz 90.9k 1MHz 39.2k 9V to 15V 3.3V 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 5.62k 550kHz 75.0k 1MHz 39.2k 9V to 15V 5V 10µF, 50V, 1210 100µF, 6.3V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 3.09k 600kHz 68.1k 1MHz 39.2k 10V to 15V 8V 10µF, 50V, 1210 1.74k 625kHz 64.9k 1MHz 39.2k 100µF, 10V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 18V to 36V 1.2V 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G Open 200kHz 200k 250kHz 169k 18V to 36V 1.5V 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 38.3k 300kHz 140k 350kHz 118k 18V to 36V 1.8V 10µF, 50V, 1210 100µF, 6.3V, 1210 470µF, 6.3V, 9mΩ, Chemi-Con, APXF6R3ARA471MH80G 19.6k 350kHz 118k 400kHz 102k 18V to 36V 2.5V 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 9.09k 450kHz 90.9k 525kHz 78.7k 18V to 36V 3.3 10µF, 50V, 1210 100µF, 6.3V, 1210 330µF, 4V, 27mΩ, OS-CON, 4SVPC330M 5.62k 550kHz 75.0k 625kHz 64.9k 18V to 36V 5V 10µF, 50V, 1210 100µF, 6.3V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 3.09k 600kHz 68.1k 700kHz 57.6k 18V to 36V 8V 10µF, 50V, 1210 100µF, 10V, 1210 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M 1.74k 625kHz 64.9k 750kHz 53.6k 18V to 36V 12V 10µF, 50V, 1210 47µF, 16V, 1210 1.10k 650kHz 61.9k 800kHz 49.9k 120µF, 16V, 27mΩ, OS-CON, 16SVPC120M Note: An input bulk capacitor is required. 8001f For more information www.linear.com/8001 13 LTM8001 APPLICATIONS INFORMATION Programming Switching Frequency Soft-Start The LTM8001 has an operational switching frequency range between 200kHz and 1MHz. This frequency is programmed with an external resistor from the RT pin to ground. Do not leave this pin open under any condition. See Table 2 for resistor values and the corresponding switching frequencies. The soft-start function controls the slew rate of the power supply output VOUT0 voltage during start-up. A controlled output voltage ramp minimizes output voltage overshoot, reduces inrush current from the VIN0 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. Table 2. RT Resistor Values and Their Resultant Switching Frequencies SWITCHING FREQUENCY (MHz) RT (kΩ) 1 39.2 0.75 53.6 0.5 82.5 0.3 140 0.2 200 Switching Frequency Trade-Offs It is recommended that the user apply the optimal RT resistor 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 LTM8001 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 LTM8001 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. Maximum Output Current Adjust The LTM8001 features an adjustable accurate current limit. To adjust the load current limit, an analog voltage is applied to the ILIM pin. Varying the voltage between 0V and 1.5V adjusts the maximum current between the minimum and the maximum current, 5.6A typical. Above 1.5V, the control voltage has no effect on the regulated inductor current. Graphs of the output current vs ILIM voltages are given in the Typical Performance Characteristics section. The LTM8001 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 = 7.47 R2 R1+R2 A convenient value of R1 may be 10k. In that case, R2 = 10 •IMAX kΩ 7.47 –IMAX Switching Frequency Synchronization The nominal switching frequency of the LTM8001 is determined by the resistor from the RT pin to GND and may be set from 200kHz 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 0.8V 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. 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. VREF LTM8001 2V R1 ILIM R2 8001 F01 Figure 1. Setting the Output Current Limit, IMAX 8001f 14 For more information www.linear.com/8001 LTM8001 APPLICATIONS INFORMATION Load Current Derating Using the ILIM Pin VOUT 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 LTM8001 uses the ILIM pin to reduce the effective regulated current in the load. While ILIM programs the regulated current in the load, it may also be configured to reduce the regulated current. The load/board temperature derating is programmed using a resistor divider with a temperature dependant resistance, as shown in Figure 2. When the board/load temperature rises, the ILIM voltage will decrease. RV RV VREF R2 LTM8001 RNTC RNTC RX RNTC RNTC RX ILIM 8001 F02 R1 (OPTION A TO D) A B C D VOUT LTM8001 FB0 RFB0 8001 F03 Figure 3. Voltage Regulation and Overvoltage Protection Feedback Connections Thermal Shutdown If the part is too hot, the LTM8001 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. UVLO and Shutdown Figure 2. Load Current Derating vs Temperature Using an NTC Resistor VOUT0 Output Overvoltage Protection The LTM8001 switching regulator uses the FB0 pin to both regulate the output voltage and to provide a high speed overvoltage lockout to avoid high voltage output conditions. If the output voltage exceeds 125% of the regulated voltage level (1.5V at the FB0 pin), the LTM8001 terminates switching and shuts down switching for a brief period. The output voltage at which output overvoltage protection engages must be greater than 1.5V and is set by the equation: 10k VOUT = 1.5V 1+ RFB0 where RFB0 is shown in Figure 3. If the output overvoltage protection engages, the LTM8001 will stop switching. If this is due to some external power source connected to VOUT0, this source will be free to pull up VOUT0. If the VOUT0 voltage exceeds the VIN0 input, an internal power diode will clamp the output to a diode drop above the input. The LTM8001 VOUT0 step-down regulator has an internal UVLO that terminates switching, resets all logic, and discharges the soft-start capacitor for input voltages below 4.2V. The LTM8001 also has a precision RUN function that enables switching when the voltage at the RUN pin rises to 1.68V and shuts down the LTM8001 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 divider resistors for programming the falling UVLO voltage and rising enable voltage (VENA) as configured in Figure 4. R2 = VENA – 1.084 UVLO 5.5µA R1= 1.55 R2 UVLO– 1.55 For more information www.linear.com/8001 8001f 15 LTM8001 APPLICATIONS INFORMATION 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. VIN LTM8001 The LTM8001 contains a step-down switching regulator that operates at a user-selectable frequency in forced continuous mode. Step-down switching regulators that operate in forced continuous mode are capable of both sinking and sourcing current to maintain output voltage regulation When the LTM8001 is sinking current, it maintains its output voltage regulation by power conversion, not power dissipation. This means that the energy provided to the LTM8001 is in turn delivered to its input power bus. There must be something on this power bus to accept or use the energy, or the LTM8001’s input voltage will rise. Left unchecked, the energy can raise the input voltage above the absolute maximum voltage rating and damage the LTM8001. VIN R2 RUN R1 8001 F04 Figure 4. UVLO Configuration Load Sharing The VOUT0 step-down switching converter operates in fixed frequency forced continuous mode, so it is able to source and sink current. It is therefore not suitable for load current sharing. The linear regulators connected to VOUT1-VOUT5 are internally ballasted and may be paralleled. To do this, simply tie the VOUTx and SETx terminals together. When the SET pins of the regulators are tied together, the RSET resistor is determined by the equation: RSET = Input Precautions VOUT n • 10µA where n is the number of linear regulator outputs tied together. All paralleled LDOs must be active in order for this equation to be true, as it is assumed that all paralleled LDOs are contributing 10µA to a single voltage set resistor. If any LDO is off or inactive, it will be unable to contribution its share of the set current and the output voltage will be lower than expected. When paralleling LDOs, tie all of the VOUTx and all of the SETx pins together. Examples are shown in the Typical Applications section. In many cases, the system load on the LTM8001 input bus will be sufficient to absorb the energy delivered by the μModule regulator. The power required by other devices will consume more than enough to make up for what the LTM8001 delivers. In cases where the LTM8001 is the largest or only power converter, this may not be true and some means may need to be devised to prevent the LTM8001’s input from rising too high. Figure 5a shows a passive crowbar circuit that will dissipate energy during momentary input overvoltage conditions. The breakdown voltage of the zener diode is chosen in conjunction with the resistor R to set the circuit’s trip point. The trip point is typically set well above the maximum VIN voltage under normal operating conditions. This circuit does not have a precision threshold, and is subject to both part-to-part and temperature variations, so it is not suitable for applications where high accuracy is required or large voltage margins are not available. The circuit in Figure 5b also dissipates energy during momentary overvoltage conditions, but is more precise than that in Figure 5a. It uses an inexpensive comparator and the VREF output of the LTM8001 to establish a reference voltage. The optional hysteresis resistor in the comparator circuit avoids MOSFET chatter. Figure 5c shows a circuit that latches on and crowbars the input in an overvoltage 8001f 16 For more information www.linear.com/8001 LTM8001 APPLICATIONS INFORMATION event. The SCR latches when the input voltage threshold is exceeded, so this circuit should be used with a fuse, as shown, or employ some other method to interrupt current from the load. As mentioned, the LTM8001 sinks current by energy conversion and not dissipation. Thus, no matter what protection circuit that is used, the amount of power that the protection circuit must absorb depends upon the amount of power at the input. For example, if the output voltage is 2.5V and can sink 5A, the input protection circuit should be designed to absorb at least 7.5W. In Figures 5a and 5b, let us say that the protection activation threshold is 30V. Then the circuit must be designed to be able to dissipate 7.5W and accept 7.5W/30V = 250mA. Figures 5a through 5c are crowbar circuits, which attempt to prevent the input voltage from rising above some level by clamping the input to GND through a power device. In some cases, it is possible to simply turn off the LTM8001 when the input voltage exceeds some threshold. This is possible when the voltage power source that drives current into VOUT never exceeds VIN. An example of this circuit is shown in Figure 5d. When the power source on the output drives VIN above a predetermined threshold, the comparator pulls down on the RUN pin and stops switching in the LTM8001. When this happens, the input capacitance needs to absorb the energy stored within the LTM8001’s internal inductor, resulting in an additional voltage rise. As shown in the Block Diagram, the internal LOAD CURRENT VIN ZENER DIODE Q LOAD CURRENT VOUT0 VIN LTM8001 GND SCR SOURCING LOAD ZENER DIODE VOUT0 LTM8001 FUSE GND SOURCING LOAD R 8001 F05a 8001 F05a Figure 5a. The MOSFET Q Dissipates Momentary Energy to GND. The Zener Diode and Resistor Are Chosen to Ensure That the MOSFET Turns On Above the Maximum VIN Voltage Under Normal Operation Figure 5c. The SCR Latches On When the Activation Threshold is Reached, So a Fuse or Some Other Method of Disconnecting the Load Should be Used LOAD CURRENT OPTIONAL HYSTERESIS RESISTOR Q + – VIN LOAD CURRENT VOUT0 VREF GND VOUT0 VIN LTM8001 LTM8001 SOURCING LOAD RUN 10µF 8001 F05b Figure 5b. The Comparator in This Circuit Activates the Q MOSFET at a More Precise Voltage Than the One Shown in Figure 5a. The Reference for the Comparator is Derived from the VREF Pin of the LTM8001 – + GND SOURCING LOAD EXTERNAL REFERENCE VOLTAGE 8001 F05d Figure 5d. This Comparator Circuit Turns Off the LTM8001 if the Input Rises Above a Predetermined Threshold. When the LTM8001 Turns Off, the Energy Stored in the Internal Inductor Will Raise VIN a Small Amount Above the Threshold. 8001f For more information www.linear.com/8001 17 LTM8001 APPLICATIONS INFORMATION inductor value is 2.2uH. If the LTM8001 negative current limit is set to 5A, for example, the energy that the input capacitance must absorb is 1/2 LI2 = 27.5μJ. Suppose the comparator circuit in Figure 5d is set to pull the RUN pin down when VTRIP = 15V. The input voltage will rise according to the capacitor energy equation: 1 C ( VIN2 – VTRIP 2 ) = 27.5µJ 2 If the total input capacitance is 10μF, the input voltage will rise to: ( 1 27.5µJ = 10µF VIN2 – 15V 2 2 VIN = 15.2V ) 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 6. The LTM8001 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. COUT4 PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8001. The LTM8001 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 6 for a suggested layout. Ensure that the grounding and heat sinking are acceptable. A few rules to keep in mind are: 3. Place the ceramic COUT0 capacitor as close as possible to the VOUT0 and GND connection of the LTM8001. The electrolytic COUT0 capacitor may be farther from the LTM8001. Place the remaining COUTx output capacitors as close as possible to the VOUTx pins. 4. Place the CIN0 and COUT0 capacitors such that their ground currents flow directly adjacent or underneath the LTM8001. 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 LTM8001. COUT2 GND GND VOUT4 VOUT5 COUT5 VOUT3 SET4 VOUT2 SET3 SET2 SET5 BIAS45 VOUT1 COUT1 SET1 VREF ILIM BIAS123 GND SYNC RT VIN45 COMP FBO VOUT0 SS RUN COUT0 1. Place the RSETx, RFB0 and RT resistors as close as possible to their respective pins. 2. Place the CIN0 capacitor as close as possible to the VIN0 and GND connection of the LTM8001. COUT3 VIN0 GND THERMAL VIAS CIN0 8001 F06 Figure 6. Layout Showing Suggested External Components, GND Plane and Thermal Vias Hot Plugging Safely The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of LTM8001. However, these capacitors can cause problems if the LTM8001 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 VIN0 pin of the LTM8001 can ring to more than twice the nominal input voltage, possibly exceeding the LTM8001’s rating 8001f 18 For more information www.linear.com/8001 LTM8001 APPLICATIONS INFORMATION and damaging the part. If the input supply is poorly controlled or the user will be plugging the LTM8001 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 VIN0, but the most popular method of controlling input voltage overshoot is to add an electrolytic bulk capacitor to the VIN0 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 performance of the circuit, though it may be physically large. Shorted Input Protection Care needs to be taken in systems where the VOUT0 output will be held high when the input to the LTM8001 is absent. If the VIN0 is allowed to float and the RUN pin is held high (either by a logic signal or because it is tied to VIN0), then the LTM8001’s internal circuitry will pull its quiescent current through its internal power switch. This is fine if your system can tolerate this state. If the RUN pin is pulled low, the input current will drop to essentially zero. However, if the VIN0 is grounded while the VOUT0 output is held high, then parasitic diodes inside the LTM8001 can pull large currents from the output through the VIN0 pin. Figure 7 shows a circuit that will run only when the input voltage is present and that protects against a shorted or reversed input. VIN VIN VOUT0 VOUT RUN LTM8001 RT GND Charging Applications The LTM8001’s internal switching step-down regulator’s CVCC operation makes it well suited for battery or supercapacitor charging applications. A schematic of the LTM8001 charging a supercapacitor and then distributing power to various loads through the onboard LDOs is shown in the Typical Applications section. In this application, the supercapacitor is charged through the step-down switching regulator and not the LDOs. Each LDO is rated for positive and differential voltages between its input and output, but may experience a negative voltage during start-up or turn-off transients if its output is connected to a battery, supercapacitor or energized load. Avoid using the LTM8001 in applications where the internal LDOs can experience a negative voltage. Thermal Considerations The LTM8001 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 LTM8001 mounted to a 59cm2 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, the Pin Configuration of this data sheet typically gives four thermal coefficients: θJA: Thermal resistance from junction to ambient 8001 F07 Figure 7. The Input Diode Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output. It Also Protects the Circuit from a Reversed Input. The LTM8001 Runs Only When the Input is Present θJCbottom: Thermal resistance from junction to the bottom of the product case 8001f For more information www.linear.com/8001 19 LTM8001 APPLICATIONS INFORMATION 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. 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 two sided, two layer board. This board is described in JESD 51-9. Given these definitions, it should now be apparent that none of these thermal coefficients reflects an actual physical operating condition of a µModule regulator. Thus, none of them can be individually used to accurately predict the thermal performance of the product. Likewise, it would be inappropriate to attempt to use any one coefficient to correlate to the junction temperature vs load graphs given in this 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 Figure 8. The blue resistances are contained within the µModule regulator, and the green are outside. The die temperature of the LTM8001 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 LTM8001. The bulk of the heat flow out of the LTM8001 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. 8001f 20 For more information www.linear.com/8001 LTM8001 APPLICATIONS INFORMATION 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 At BOARD-TO-AMBIENT RESISTANCE 8001 F08 µMODULE DEVICE Figure 8. Thermal Resistances Among μModule Device Printed Circuit Board and Ambient Environment 8001f For more information www.linear.com/8001 21 LTM8001 TYPICAL APPLICATIONS Five Output DC/DC µModule Regulator BIAS45 BIAS123 VIN45 VIN 18V TO 36V 10µF VOUT0 VIN0 510k LDO 1 RUN COMP SS VREF ILIM SYNC LTM8001 12V1 300mA VOUT1 SET1 12V2 300mA VOUT2 STEP-DOWN LDO 2 SET2 SWITCHING V REGULATOR LDO 3 OUT3 SET3 LDO 4 GND (13.5V) 68.1k 953Ω 120µF + 12V3 300mA 12V4 300mA VOUT4 SET4 VOUT5 FBO LDO 5 SET5 RT 47µF 2.2µF 2.2µF 2.2µF 2.2µF 2.2µF 1.21M 1.21M 1.21M 1.21M 1.21M 12V5 300mA 8001 TA02 600kHz 8001f 22 For more information www.linear.com/8001 LTM8001 TYPICAL APPLICATIONS Dual Input, 2.5V 5A DC/DC µModule Converter Using a Single LTM8001 (External 3.3V Turns On Before or Simultaneously with 12V) EXTERNAL 3.3V VIN 12V 10µF 10µF VIN45 VOUT0 VIN0 510k LDO 1 RUN BIAS123 BIAS45 LTM8001 COMP SS VREF ILIM SYNC GND + VOUT1 SET1 VOUT4 SET4 VOUT5 FBO LDO 5 SET5 RT 82.5k 6.65k 500kHz 470µF 100µF VOUT2 STEP-DOWN LDO 2 SET2 SWITCHING V REGULATOR LDO 3 OUT3 SET3 LDO 4 3V 22µF 10nF 2.5V 5A 49.9k 8001 TA03 8001f For more information www.linear.com/8001 23 LTM8001 TYPICAL APPLICATIONS Supercapacitor Charger and Two Output Regulator VIN45 VIN 9V TO 15V 10µF VOUT0 VIN0 200k 48.7k RUN BIAS123 BIAS45 LTM8001 COMP SS VREF ILIM SYNC GND LDO 1 3.3V 1A VOUT1 SET1 VOUT2 STEP-DOWN LDO 2 SET2 SWITCHING V REGULATOR LDO 3 OUT3 SET3 LDO 4 68.1k 3.09k 2.5V 0.5A VOUT4 SET4 VOUT5 FBO LDO 5 SET5 RT 47µF 5V 1.5F 5V SUPERCAP PM-5ROV155-R 4.7µF 10µF 124k 110k 600kHz 8001 TA04 8001f 24 For more information www.linear.com/8001 LTM8001 TYPICAL APPLICATIONS Use Two LTM8001s to Implement a 2.5VOUT 10A DC/DC µModule Converter 100µF VIN45 VIN1 12V 10µF ×2 LDO 1 RUN BIAS123 BIAS45 LTM8001 COMP SS VREF ILIM SYNC GND 3V 470µF VOUT0 VIN0 510k + 2.5V 10A VOUT1 SET1 VOUT2 STEP-DOWN LDO 2 SET2 SWITCHING V REGULATOR LDO 3 OUT3 SET3 LDO 4 VOUT4 SET4 VOUT5 FBO LDO 5 SET5 RT 82.5k 6.65k 22µF 500kHz 100µF VIN45 3V 470µF VOUT0 VIN0 LDO 1 RUN BIAS123 BIAS45 LTM8001 COMP SS VREF ILIM SYNC GND + VOUT1 SET1 VOUT2 STEP-DOWN LDO 2 SET2 SWITCHING V REGULATOR LDO 3 OUT3 SET3 LDO 4 VOUT4 SET4 VOUT5 FBO LDO 5 SET5 RT 82.5k 6.65k 500kHz 24.9k 8001 TA05 8001f For more information www.linear.com/8001 25 0.635 ±0.025 Ø 121x PACKAGE TOP VIEW 2.540 SUGGESTED PCB LAYOUT TOP VIEW 1.270 4 0.3175 0.000 0.3175 PIN “A1” CORNER E 1.270 aaa Z 2.540 D X For more information www.linear.com/8001 6.350 5.080 3.810 2.540 1.270 0.000 1.270 2.540 3.810 5.080 6.350 Y aaa Z SYMBOL A A1 A2 b b1 D E e F G H1 H2 aaa bbb ccc ddd eee H1 SUBSTRATE NOM 3.42 0.60 2.82 0.75 0.63 15.00 15.00 1.27 12.70 12.70 0.32 2.50 MAX 3.62 0.70 2.92 0.90 0.66 NOTES DETAIL B PACKAGE SIDE VIEW 0.37 2.55 0.15 0.10 0.20 0.30 0.15 TOTAL NUMBER OF BALLS: 121 0.27 2.45 MIN 3.22 0.50 2.72 0.60 0.60 b1 DIMENSIONS ddd M Z X Y eee M Z DETAIL A Øb (121 PLACES) DETAIL B H2 MOLD CAP ccc Z A1 A2 A (Reference LTC DWG# 05-08-1923 Rev Ø) // bbb Z 26 Z Z BGA Package 121-Lead (15.00mm × 15.00mm × 3.42mm) F 11 10 9 7 6 5 4 PACKAGE BOTTOM VIEW 8 G 3 2 1 DETAIL A DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE BALL DESIGNATION PER JESD MS-028 AND JEP95 L K J H G F E D C B A TRAY PIN 1 BEVEL BGA 121 0512 REV Ø PACKAGE IN TRAY LOADING ORIENTATION LTMXXXXXX µModule 6. SOLDER BALL COMPOSITION CAN BE 96.5% Sn/3.0% Ag/0.5% Cu OR Sn Pb EUTECTIC 5. PRIMARY DATUM -Z- IS SEATING PLANE 4 3 2. ALL DIMENSIONS ARE IN MILLIMETERS NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 e COMPONENT PIN “A1” b 3 SEE NOTES PIN 1 LTM8001 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. 8001f 6.350 5.080 3.810 3.810 5.080 6.350 LTM8001 PACKAGE DESCRIPTION Table 3. LTM8001 Pinout (Sorted by Pin Number) PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME A1 GND B1 GND C1 GND D1 GND E1 GND F1 GND A2 GND B2 GND C2 GND D2 GND E2 GND F2 GND A3 VOUT0 B3 VOUT0 C3 VOUT0 D3 GND E3 GND F3 GND A4 VOUT0 B4 VOUT0 C4 VOUT0 D4 GND E4 GND F4 GND A5 VOUT0 B5 VOUT0 C5 VOUT0 D5 GND E5 GND F5 GND A6 VIN45 B6 VIN45 C6 VIN45 D6 GND E6 GND F6 GND A7 VIN45 B7 VIN45 C7 VIN45 D7 GND E7 GND F7 GND A8 BIAS45 B8 BIAS123 C8 GND D8 GND E8 GND F8 GND A9 SET5 B9 GND C9 GND D9 GND E9 GND F9 GND A10 VOUT5 B10 GND C10 GND D10 GND E10 GND F10 GND A11 VOUT5 B11 VOUT4 C11 VOUT4 D11 SET4 E11 VOUT3 F11 VOUT3 PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME G1 GND H1 GND J1 VIN0 K1 VIN0 L1 VIN0 G2 GND H2 GND J2 VIN0 K2 VIN0 L2 VIN0 G3 GND H3 GND J3 VIN0 K3 VIN0 L3 VIN0 G4 GND H4 GND J4 GND K4 SS L4 RUN G5 GND H5 GND J5 GND K5 GND L5 FB0 G6 GND H6 GND J6 GND K6 GND L6 COMP G7 GND H7 GND J7 GND K7 SYNC L7 RT G8 GND H8 GND J8 GND K8 VREF L8 ILIM G9 GND H9 GND J9 GND K9 GND L9 SET1 G10 GND H10 GND J10 GND K10 GND L10 VOUT1 G11 SET3 H11 SET2 J11 VOUT2 K11 VOUT2 L11 VOUT1 PACKAGE PHOTO 8001f 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 its circuits as described herein will not infringe on existing patent rights. Forofmore information www.linear.com/8001 27 LTM8001 TYPICAL APPLICATION Three Output DC/DC µModule Converter VIN45 VIN 9V TO 18V 10µF VIN0 510k 10k LDO 1 RUN BIAS123 BIAS45 LTM8001 COMP SS VREF ILIM SYNC GND 1.8V 1A 1V 2.2A VOUT0 VOUT1 SET1 VOUT2 STEP-DOWN LDO 2 SET2 SWITCHING V REGULATOR LDO 3 OUT3 SET3 LDO 4 VOUT5 FBO LDO 5 SET5 RT 20.5k 118k 1.2V 1.3A VOUT4 SET4 19.6k 4.7µF 10µF 60.4k 33.2k 470µF + 100µF 8001 TA06 350kHz RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTM8026 36VIN, 5A Step-Down µModule Regulator with Adjustable Current Limit 6V ≤ VIN ≤ 36V, 1.2V ≤ VOUT ≤ 24V, Adjustable Current Limit, Parallelable Outputs, CLK Input, 11.25mm × 15mm × 2.82mm LGA LTM8052 36VIN, ±5A Step-Down µModule Regulator with Adjustable Current Limit 6V ≤ VIN ≤ 36V, 1.2V ≤ VOUT ≤ 24V, –5V ≤ IOUT ≤ 5A, Adjustable Current Limit, CLK Input, 11.25mm × 15mm × 2.82mm LGA, Pin Compatible with LTM8026 LTM8061 32V, 2A Step-Down µModule Battery Charger with Programmable Input Current Limit Suitable for CC-CV Charging Single and Dual Cell Li-Ion or Li-Poly Batteries, 4.95V ≤ VIN ≤ 32V, C/10 or Adjustable Timer Charge Termination, NTC Resistor Monitor Input, 9mm × 15mm × 4.32mm LGA LTM8062A 32V, 2A Step-Down µModule Battery Charger with Integrated Maximum Peak Power Tracking (MPPT) for Solar applications Suitable for CC-CV Charging Method Battery Chemistries (Li-Ion, Li-Poly, Lead-Acid, LiFePO4), User Adjustable MPPT Servo Voltage, 4.95V ≤ VIN ≤ 32V, 3.3V ≤ VBATT ≤ 18.8V Adjustable, C/10 or Adjustable Timer Charge Termination, NTC Resistor Monitor Input, 9mm × 15mm × 4.32mm LGA LTM8033 36V, 3A EN55022 Class B Certified DC/DC Step-Down µModule Regulator 3.6V ≤ VIN ≤ 36V, 0.8V ≤ VOUT ≤ 24V, Synchronizable, 11.25mm × 15mm × 4.32mm LGA LTM4613 36VIN, 8A EN55022 Class B Certified DC/DC StepDown µModule Regulator 5V ≤ VIN ≤ 36V, 3.3V ≤ VOUT ≤ 15V, PLL input, VOUT Tracking and Margining, 15mm × 15mm × 4.32mm LGA LTM8048 1.5W, 725VDC Galvanically Isolated µModule Converter 3.1V ≤ VIN ≤ 32V, 2.5V ≤ VOUT ≤ 12V, 1mVP-P Output Ripple, Internal Isolated Transformer, 9mm × 11.25mm × 4.92mm BGA with LDO Post regulator LTC2978 Octal Digital Power Supply Manager with EEPROM I2C/PMBus Interface, Configuration EEPROM, Fault Logging, 16-Bit ADC with ±0.25% TUE, 3.3V to 15V Operation LTC2974 Quad Digital Power Supply Manager with EEPROM I2C/PMBus Interface, Configuration EEPROM, Fault Logging, per Channel Voltage, Current and Temperature Measurements LTC3880 Dual Output PolyPhase® Step-Down DC/DC Controller with Digital Power System Management I2C/PMBus Interface, Configuration EEPROM, Fault Logging, ±0.5% Output Voltage Accuracy, MOSFET Gate Drivers 8001f 28 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/8001 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/8001 LT 0213 • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2013