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For more information www.linear .com/L TM4637 TYPICAL APPLICATION
DESCRIPTION
20A DC/DC µModule Step-Down Regulator The LT M®4637 is a complete 20A output high efficiency switch mode step-down DC/DC µModule (micromodule) regulator. Included in the package are the switching control- ler, power FETs, inductor and compensation components. Operating over an input voltage range from 4.5V to 20V, the LTM4637 supports an output voltage range of 0.6V to 5.5V, set by a single external resistor. Only a few input and output capacitors are needed. Current mode operation allows precision current sharing of up to four LTM4637 regulators to obtain up to 80A output . High switching frequency and a current mode architecture enable a very fast transient response to line and load changes without sacrificing stability. The device supports frequency synchronization, multiphase/current sharing, Burst Mode operation and output voltage tracking for supply rail sequencing. A diode-connected PNP transis- tor is available for use as an internal temperature monitor. The LTM4637 is offered in a 15mm × 15mm × 4.32mm LGA package. The LTM4637 is RoHS compliant. The LTM4637 is pin compatible with the LTM4627, a 15A DC/DC µModule regulator. L, LT, LT C, LT M, PolyPhase, Burst Mode, µModule, Linear Technology, the Linear logo are registered trademarks and L TpowerCAD is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 5847554, 6580258, 6304066, 6476589, 6774611, 6677210. 12VIN, 1.2VOUT, 20A DC/DC µModule® Regulator
FEATURES
APPLICATIONS
n Complete 20A Switch Mode Power Supply n 4.5V to 20V Input Voltage Range n 0.6V to 5.5V Output Voltage Range n ±1.5% Total DC Output Voltage Error (–40°C to 125°C) n Differential Remote Sense Amplifier for Precision Regulation for (V OUT ≤ 3.3V) n Current Mode Control/Fast T ransient Response n Parallel Current Sharing (Up to 80A) n Frequency Synchronization n Selectable Pulse-Skipping or Burst Mode® Operation n Soft-Start/Voltage T racking n Up to 88% Efficiency (12VIN, 1.8VOUT) n Overcurrent Foldback Protection n Output Overvoltage Protection n Internal Temperature Monitor n Overtemperature Protection n 15mm × 15mm × 4.32mm LGA Package n Telecom Servers and Networking Equipment n Industrial Equipment n Medical Systems n High Ambient Temperature Systems 12VIN Efficiency vs Load Current COMP TRACK/SS RUN f SET MODE_PLLIN TEMP PGOOD V OUT VOUT_LCL DIFF_OUT VOSNS+ VOSNS– VFB L TM4637 VIN10k RFB** 60.4k 22µF 16V 0.1µF 100µF* 6.3V 470µF 6.3V V OUT 1.2V 20A 330pF INTV CC 2.2µF EXTVCC * SEE TABLE 5 ** SEE TABLE 1
4637 TA01a
OUTPUT CURRENT (A) EFFICIENCY (%) 100 2 10 14
4637 TA01b
1.2VOUT 250kHz CCM
For more information www.linear .com/L TM4637 PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS MODE_PLLIN, fSET, TRACK/SS, Internal Operating Temperature Range (Note 1)
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VIN Input DC Voltage l 4.5 20 V VOUT Range VOUT Range l 0.6 5.5 V VOUT(DC) Output Voltage, Total Variation with Line and Load CIN = 22µF × 3 COUT = 100µF Ceramic, 470µF POSCAP RFB = 40.2k, MODE_PLLIN = GND VIN = 5V to 20V, IOUT = 0A to 20A (Note 4) l 1.477 1.50 1.523 V Input Specifications VRUN RUN Pin On Threshold VRUN Rising 1.1 1.25 1.4 V VRUNHYS RUN Pin On Hysteresis 130 mV The l denotes the specifications which apply over the full internal operating temperature range (Note 2), otherwise specifications are at TA = 25°C. VIN = 12V, per the typical application in Figure 22. ORDER INFORMATION LEAD FREE FINISH TRAY PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTM4637EV#PBF LTM4637EV#PBF LTM4637V 133-Lead (15mm × 15mm × 4.32mm) LGA –40°C to 125°C LTM4637IV#PBF LTM4637IV#PBF LTM4637V 133-Lead (15mm × 15mm × 4.32mm) LGA –40°C to 125°C Consult LT C 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/ LGA PACKAGE 133-LEAD (15mm × 15mm × 4.32mm) VIN 1 2 3 4 5 6 7 8 10 9 11 12 B C D E F G H J K L A M INTVCC fSET COMPTRACK/SS MODE_PLLIN INTVCC TOP VIEW SGND VOUT VIN GND EXTVCC VFB PGOOD PGOOD TEMP RUN VOSNS+ DIFF_OUT VOUT_LCL VOSNS– TJ(MAX) = 125°C, θJA = 9.5°C/W, θJCbottom = 4°C/W, θJCtop = 6.7°C/W, θJB = 4.5°C/W θJA DERIVED FROM 95mm × 76mm PCB WITH 4 LAYERS; WEIGHT = 2.9g θ VALUES DETERMINED PER JESD51-12
For more information www.linear .com/L TM4637 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full internal operating temperature range (Note 2), otherwise specifications are at TA = 25°C. VIN = 12V, per the typical application in Figure 22. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IQ(VIN) Input Supply Bias Current VIN = 12V, VOUT = 1.5V, Burst Mode Operation, IOUT = 0.1A VIN = 12V, VOUT = 1.5V, Pulse-Skipping Mode, IOUT = 0.1A VIN = 12V, VOUT = 1.5V, Switching Continuous, IOUT = 0.1A Shutdown, RUN = 0, VIN = 12V mA mA mA µA I S(VIN) Input Supply Current VIN = 5V, VOUT = 1.5V, IOUT = 20A VIN = 12V, VOUT = 1.5V, IOUT = 20A 6.8 2.87 A A Output Specifications I OUT(DC) Output Continuous Current Range VIN = 12V, VOUT = 1.5V (Note 4) 0 20 A ∆VOUT (Line) VOUT Line Regulation Accuracy VOUT = 1.5V, VIN from 4.5V to 20V IOUT = 0A l 0.02 0.06 %/V ∆VOUT (Load) VOUT Load Regulation Accuracy VOUT = 1.5V, IOUT = 0A to 20A, VIN = 12V (Note 4) l 0.2 0.45 % VOUT(AC) Output Ripple Voltage IOUT = 0A, COUT = 100µF Ceramic, 470µF POSCAP VIN = 12V, VOUT = 1.5V 30 mVP-P ∆VOUT(START) Turn-On Overshoot COUT = 100µF Ceramic, 470µF POSCAP, VOUT = 1.5V, IOUT = 0A, VIN = 12V 15 mV tSTART Turn-On Time COUT = 100µF Ceramic, 470µF POSCAP, No Load, TRACK/SS = 0.001µF, VIN = 12V 0.6 ms ∆VOUTLS Peak Deviation for Dynamic Load Load: 0% to 50% to 0% of Full Load COUT = 100µF × 2 Ceramic, 470µF × 3 POSCAP, VIN = 12V, VOUT = 1.5V 50 mV tSETTLE Settling Time for Dynamic Load Step Load: 0% to 50% to 0% of Full Load, V IN = 5V, COUT = 100µF × 2 Ceramic, 470µF × 3 POSCAP 50 µs IOUTPK Output Current Limit VIN = 12V, VOUT = 1.5V VIN = 5V, VOUT = 1.5V A A Control Section V FB Voltage at VFB Pin IOUT = 0A, VOUT = 1.5V l 0.594 0.60 0.606 V IFB Current at VFB Pin (Note 7) –12 –25 nA VOVL Feedback Overvoltage Lockout l 0.65 0.67 0.69 V ITRACK/SS T rack Pin Soft-Start Pull-Up Current TRACK/SS = 0V 1.0 1.2 1.4 µA t ON(MIN) Minimum On-Time (Note 3) 100 ns RFBHI Resistor Between VOUT_LCL and VFB Pins 60.05 60.40 60.75 kΩ Remote Sense Amplifier VOSNS+, VOSNS– CM RANGE Common Mode Input Range VIN = 12V, Run > 1.4V 0 3.6 V VDIFF_OUT(MAX) Maximum DIFF_OUT Voltage IDIFF_OUT = 300µA INTVCC – 1.4 V VOS Input Offset Voltage VOSNS+ = VDIFF_OUT = 1.5V, IDIFF_OUT = 100µA 2 mV AV Differential Gain (Note 7) 1 V/V SR Slew Rate (Note 6) 2 V/µs GBP Gain Bandwidth Product (Note 6) 3 MHz CMRR Common Mode Rejection (Note 7) 60 dB IDIFF_OUT DIFF_OUT Current Sourcing 2 mA
For more information www.linear .com/L TM4637 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS PSRR Power Supply Rejection Ratio 5V < VIN < 20V (Note 7) 100 dB RIN Input Resistance VOSNS+ to GND 80 kΩ PGOOD Output VPGOOD PGOOD T rip Level VFB With Respect to Set Output VFB Ramping Negative VFB Ramping Positive –10 V PGL PGOOD Voltage Low IPGOOD = 2mA 0.1 0.3 V INTVCC Linear Regulator VINTVCC Internal VCC Voltage 6V < VIN < 20V 4.8 5 5.2 V VINTVCC Load Reg INTVCC Load Regulation ICC = 0 to 50mA 0.5 % VEXTVCC External VCC Switchover EXTVCC Ramping Positive l 4.5 4.7 V VLDO Ext EXTVCC Voltage Drop ICC = 25mA, VEXTVCC = 5V 50 100 mV Oscillator and Phase-Locked Loop fSYNC Frequency Sync Capture Range MODE_PLLIN Clock Duty Cycle = 50% 250 800 kHz fNOM Nominal Frequency VfSET = 1.2V 450 500 550 kHz fLOW Lowest Frequency VfSET = 0V 210 250 290 kHz fHIGH Highest Frequency VfSET ≥ 2.4V 700 770 850 kHz IFREQ Frequency Set Current 9 10 11 µA RMODE_PLLIN MODE_PLLIN Input Resistance 250 kΩ V IH_MODE_PLLIN Clock Input Level High 2.0 V VIL_MODE_PLLIN Clock Input Level Low 0.8 V Temperature Diode VTEMP TEMP Diode Voltage ITEMP = 100µA 0.6 V TC VTEMP Temperature Coefficient l –2.2 mV/°C ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full internal operating temperature range (Note 2), otherwise specifications are at TA = 25°C. VIN = 12V, per the typical application in Figure 22. 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 LTM4637 is tested under pulsed load conditions such that TJ ≈ TA. The LTM4637E is guaranteed to meet performance specifications over the 0°C to 125°C internal operating temperature range. 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 LTM4637I is guaranteed to meet specifications over the full –40°C to 125°C internal operating temperature range. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. Note 3: The minimum on-time condition is specified for a peak-to-peak inductor ripple current of ~40% of I MAX Load. (See the Applications Information section) Note 4: See output current derating curves for different VIN, VOUT and TA. Note 5: Limit current into the RUN pin to less than 2mA. Note 6: Guaranteed by design. Note 7: 100% tested at wafer level.
For more information www.linear .com/L TM4637 TYPICAL PERFORMANCE CHARACTERISTICS Burst Mode Efficiency vs Load Current Pulse-Skipping Mode Efficiency vs Load Current 1V T ransient Response 1.2V T ransient Response 1.5V T ransient Response 1.8V T ransient Response Efficiency vs Load Current with 5V IN Efficiency vs Load Current with IN (Limit 5V Output to 15A) Efficiency vs Load Current with 12V IN (Limit 5V Output to 15A) OUTPUT CURRENT (A) EFFICIENCY (%) 100 2 10 14
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1VOUT, 250kHz, CCM 1.2VOUT, 250kHz, CCM 1.5VOUT, 350kHz, CCM 1.8VOUT, 350kHz, CCM 2.5VOUT, 450kHz, CCM 3.3VOUT, 600kHz, CCM OUTPUT CURRENT (A) EFFICIENCY (%) 100 2 10 14
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1VOUT, 250kHz, CCM 1.2VOUT, 250kHz, CCM 1.5VOUT, 350kHz, CCM 1.8VOUT, 350kHz, CCM 2.5VOUT, 450kHz, CCM 3.3VOUT, 600kHz, CCM 5VOUT, 600kHz, CCM OUTPUT CURRENT (A) EFFICIENCY (%) 100 2 10 14
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1VOUT, 250kHz, CCM 1.2VOUT, 250kHz, CCM 1.5VOUT, 350kHz, CCM 1.8VOUT, 350kHz, CCM 2.5VOUT, 450kHz, CCM 3.3VOUT, 600kHz, CCM 5VOUT, 600kHz, CCM OUTPUT CURRENT (A) EFFICIENCY (%) 0.5 1 1.5 2
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2.5 3 5VIN, 1.8VOUT, 350kHz 8VIN, 1.8VOUT, 350kHz 12VIN, 1.8VOUT, 350kHz OUTPUT CURRENT (A) EFFICIENCY (%) 0.5 1 1.5 2
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2.5 3 5VIN, 1.8VOUT, 350k 8VIN, 1.8VOUT, 350k 12VIN, 1.8VOUT, 350k OUTPUT TRANSIENT 50mV/DIV 200µs/DIV LOAD STEP 5A/DIV 200µs/DIVVIN = 12V VOUT = 1V IOUT = 0A TO 10A, CFF = 330pF OUTPUT CAPACITORS: 3 × 470µF POSCAP CAPACITORS 2 × 100µF CERAMIC CAPACITORS
4637 G06
200µs/DIV LOAD STEP 5A/DIV 200µs/DIVVIN = 12V VOUT = 1.2V IOUT = 0A TO 10A, CFF = 330pF OUTPUT CAPACITORS: 3 × 470µF POSCAP CAPACITORS 2 × 100µF CERAMIC CAPACITORS
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200µs/DIV LOAD STEP 5A/DIV 200µs/DIVVIN = 12V VOUT = 1.5V IOUT = 0A TO 10A, CFF = 330pF OUTPUT CAPACITORS: 3 × 470µF POSCAP CAPACITORS 2 × 100µF CERAMIC CAPACITORS
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200µs/DIV LOAD STEP 5A/DIV 200µs/DIVVIN = 12V VOUT = 1.8V IOUT = 0A TO 10A, CFF = 330pF OUTPUT CAPACITORS: 3 × 470µF POSCAP CAPACITORS 2 × 100µF CERAMIC CAPACITORS
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For more information www.linear .com/L TM4637 TYPICAL PERFORMANCE CHARACTERISTICS 2.5V T ransient Response Turn-On No Load Short-Circuit Protection No Load 3.3V T ransient Response Turn-On 20A Load Short-Circuit Protection with 20A Load 5V T ransient Response OUTPUT TRANSIENT 50mV/DIV 200µs/DIV LOAD STEP 5A/DIV 200µs/DIVVIN = 12V VOUT = 2.5V IOUT = 0A TO 10A, CFF = 330pF OUTPUT CAPACITORS: 3 × 470µF POSCAP CAPACITORS 2 × 100µF CERAMIC CAPACITORS
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200µs/DIV LOAD STEP 5A/DIV 200µs/DIVVIN = 12V VOUT = 3.3V IOUT = 0A TO 10A, CFF = 330pF OUTPUT CAPACITORS: 3 × 470µF POSCAP CAPACITORS 2 × 100µF CERAMIC CAPACITORS
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200µs/DIV LOAD STEP 5A/DIV 200µs/DIVVIN = 12V VOUT = 5V IOUT = 0A TO 10A, CFF = 330pF OUTPUT CAPACITORS: 3 × 470µF POSCAP CAPACITORS 2 × 100µF CERAMIC CAPACITORS
4637 G12
12V to 1.5V AT 0A LOAD TRACK/SS = 0.1µF
4637 G13
12V to 1.5V AT 20A LOAD TRACK/SS = 0.1µF
4637 G14
200µs/DIV INPUT CURRENT 200mA/DIV 200µs/DIV 12V to 1.5V AT 0A LOAD TRACK/SS = 0.1µF
4637 G15
200µs/DIV INPUT CURRENT 1A/DIV 200µs/DIV 12V to 1.5V AT 20A LOAD TRACK/SS = 0.1µF
4637 G16
For more information www.linear .com/L TM4637 PIN FUNCTIONS VIN (A1-A6, B1-B6, C1-C6): Power Input Pins. Apply input voltage between these and GND pins. Recommend placing input decoupling capacitance directly between VIN and GND pins. VOUT (J1-J10, K1-K11, L1-L11, M1-M11): Power Output Pins. Apply output load between these and GND pins. Rec- ommend placing output decoupling capacitance between these pins and GND pins. Review Table 5. GND (B7, B9, C7, C9, D1-D6, D8, E1-E7, E9, F1-F9, G1-G9, H1-H9): Power Ground Pins for Both Input and Output. PGOOD (F11, G12): Output Voltage Power Good Indica- tor. Open-drain logic output is pulled to ground when the output voltage exceeds a ±10% regulation window. Both pins are tied together internally. SGND ( G11, H11, H12): Signal Ground Pin. Return ground path for all analog and low power circuitry. Tie a single connection to the output capacitor GND. See layout guidelines in Figure 21. TEMP ( D10): Temperature Monitor. See Applications Information section. MODE_PLLIN (A8): Forced Continuous Mode, Burst Mode Operation, or Pulse-Skipping Mode Selection Pin and External Synchronization Input to Phase Detector Pin. Connect this pin to INTV CC to enable pulse-skipping mode. Connect to ground to enable forced continuous mode. Floating this pin will enable Burst Mode operation. A clock on this pin will enable synchronization with forced continu- ous operation. See the Applications Information section. fSET (B12): A resistor can be applied from this pin to ground to set the operating frequency, or a DC voltage can be applied to set the frequency. See the Applications Information section. TRACK/SS (A9): Output Voltage T racking Pin and Soft- Start Inputs. The pin has a 1.2µA pull-up current source. A capacitor from this pin to ground will set a soft-start ramp rate. In tracking, the regulator output can be tracked to a different voltage. See the Applications Information section. VFB (F12): The Negative Input of the Error Amplifier. Internally, this pin is connected to VOUT_LCL with a 60.4k precision resistor. Different output voltages can be programmed with an additional resistor between VFB and ground pins. In PolyPhase® operation, tying the VFB pins together allows for parallel operation. See the Applications Information section. COMP (A11): Current Control Threshold and Error Amplifier Compensation Point. The current comparator threshold increases with this control voltage. Tie all COMP pins together for parallel operation. The device is internally compensated. RUN: (A10) Run Control Pin. A voltage above 1.4V will turn on the module. A 5.1V Zener diode to ground is internal to the module for limiting the voltage on the RUN pin to 5V, and allowing a pull-up resistor to V IN for enabling the device. Limit current into the RUN pin to ≤ 2mA. INTV CC: (A7, D9) Internal 5V LDO for Driving the Control Circuitry and the Power MOSFET Drivers. Both pins are internally connected. The 5V LDO has a 100mA current limit. INTVCC is controlled and enabled when RUN is activated high. EXTV CC (E12): External power input to an internal control switch allows an external source greater than 4.7V, but less than 6V to supply IC power and bypass the internal INTVCC LDO. EXTVCC must be less than VIN at all times during power-on and power-off sequences. See the Applications Information section. 5V output application can connect the 5V output to this pin to improve efficiency. The 5V output is connected to EXTVCC in the 5V derating curves. VOUT_LCL: (L12) This pin connects to VOUT through a 1M resistor, and to VFB with a 60.4k resistor. The remote sense amplifier output DIFF_OUT is connected to VOUT_LCL, and drives the 60.4k top feedback resistor in remote sensing applications. When the remote sense amplifier is used, DIFF_OUT effectively eliminates the 1MΩ from VOUT to VOUT_LCL. When the remote sense amplifier is not used, then connect VOUT_LCL to VOUT directly. PACKAGE ROW AND COLUMN LABELING MAY VARY AMONG µModule PRODUCTS. REVIEW EACH PACKAGE LAYOUT CAREFULL Y.
Figure 1. Simplified LTM4637 Block Diagram
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VOSNS+: (J12) (+) Input to the Remote Sense Amplifier. nect to ground when not used. VOSNS–: (M12) (–) Input to the Remote Sense Amplifier. nect to ground when not used. DIFF_OUT: (K12) Output of the Remote Sense Amplifier. sense amplifier can be used for VOUT ≤ 3.3V.
For more information www.linear .com/L TM4637 DECOUPLING REQUIREMENTS SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS CIN External Input Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 1.5V) IOUT = 20A, 4× 22µF Ceramic X7R Capacitors (See Table 5) 88 µF COUT External Output Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 1.5V) IOUT = 20A (See Table 5) 400 µF TA = 25°C. Use Figure 1 configuration . Power Module Description The LTM4637 is a high performance single output stand- alone nonisolated switching mode DC/DC power supply. It can provide a 20A output with few external input and output capacitors. This module provides precisely regu- lated output voltages programmable via external resistors from 0.6VDC to 5.5VDC over a 4.5V to 20V input range. The typical application schematic is shown in Figure 22. The LTM4637 has an integrated constant-frequency cur- rent mode regulator, power MOSFETs, 0.6µH inductor, and other supporting discrete components. The switching frequency range is from 250kHz to 770kHz, and the typical operating frequency is shown in Table 5 for each VOUT. For switching noise-sensitive applications, it can be externally synchronized from 250kHz to 800kHz, subject to minimum on-time limitations. A single resistor is used to program the frequency. See the Applications Information section. With current mode control and internal feedback loop compensation, the LTM4637 module has sufficient stabil- ity margins and good transient performance with a wide range of output capacitors, even with all ceramic output capacitors. Current mode control provides cycle-by-cycle fast current limit in an overcurrent condition. An internal overvoltage monitor protects the output voltage in the event of an overvoltage >10%. The top MOSFET is turned off and the bottom MOSFET is turned on until the output is cleared. OPERATION Overtemperature protection will turn off the regulator’s RUN pin at ~130°C to 137°C. See Applications Information. Pulling the RUN pin below 1.1V forces the regulator into a shutdown state. The TRACK/SS pin is used for program- ming the output voltage ramp and voltage tracking during start-up. See the Application Information section. The LTM4637 is internally compensated to be stable over all operating conditions. Table 5 provides a guideline for input and output capacitances for several operating condi- tions. L TpowerCAD™ is available for transient and stability analysis. The VFB pin is used to program the output voltage with a single external resistor to ground. A remote sense amplifier is provided for accurately sensing output voltages ≤3.3V at the load point. Multiphase operation can be easily employed with the synchronization inputs using an external clock source. See application examples. High efficiency at light loads can be accomplished with selectable Burst Mode operation using the MODE_PLLIN pin. These light load features will accommodate battery operation. Efficiency graphs are provided for light load op- eration in the Typical Performance Characteristics section. A TEMP pin is provided to allow the internal device tem- perature to be monitored using an onboard diode connected PNP transistor.
mined by the maximum load current and output voltage. for particular applications. at very low input voltage and high duty cycle applications. temperature derating curves. Table 1. VFB Resistor Table vs Various Output Voltages COMP pins must be tied together also. good choice with RMS ripple current ratings of ~ 2A each. capacitor can be used for more input bulk capacitance. planes are used, then this bulk capacitor is not needed. electrolytic capacitor or a Polymer capacitor.
For more information www.linear .com/L TM4637 to optimize the transient performance. Stability criteria are considered in the Table 5 matrix, and L TpowerCAD is available for stability analysis. Multiphase operation will reduce effective output ripple as a function of the number of phases. Application Note 77 discusses this noise reduction versus output ripple current cancellation, but the output capacitance should be considered carefully as a function of stability and transient response. L TpowerCAD can be used to calculate the output ripple reduction as the number of implemented phases increase by N times. Burst Mode Operation The LTM4637 is capable of Burst Mode operation in which the power MOSFETs operate intermittently based on load demand, thus saving quiescent current. For applications where maximizing the efficiency at very light loads is a high priority, Burst Mode operation should be applied. To enable Burst Mode operation, simply float the MODE_PLLIN pin. During Burst Mode operation, the peak current of the inductor is set to approximately 30% of the maximum peak current value in normal operation even though the voltage at the COMP pin indicates a lower value. The voltage at the COMP pin drops when the inductor’s average current is greater than the load requirement. As the COMP voltage drops below 0.5V, the burst comparator trips, causing the internal sleep line to go high and turn off both power MOSFETs. In sleep mode, the internal circuitry is partially turned off, reducing the quiescent current. The load current is now being supplied from the output capacitors. When the output voltage drops, causing COMP to rise, the internal sleep line goes low, and the LTM4637 resumes normal operation. The next oscillator cycle will turn on the top power MOSFET and the switching cycle repeats. Pulse-Skipping Mode Operation In applications where low output ripple and high efficiency at intermediate currents are desired, pulse-skipping mode should be used. Pulse-skipping operation allows the LTM4637 to skip cycles at low output loads, thus increasing efficiency by reducing switching loss. Tying the MODE_PLLIN pin to INTVCC enables pulse-skipping operation. With pulse-skipping mode at light load, the internal current comparator may remain tripped for several cycles, thus skipping operation cycles. This mode has lower ripple than Burst Mode operation and maintains a higher frequency operation than Burst Mode operation. Forced Continuous Operation In applications where fixed frequency operation is more critical than low current efficiency, and where the lowest output ripple is desired, forced continuous operation should be used. Forced continuous operation can be enabled by tying the MODE_PLLIN pin to ground. In this mode, inductor current is allowed to reverse during low output loads, the COMP voltage is in control of the current comparator threshold throughout, and the top MOSFET always turns on with each oscillator pulse. During start-up, forced continuous mode is disabled and inductor current is prevented from reversing until the LTM4637’s output voltage is in regulation. Multiphase Operation For outputs that demand more than 20A of load current, multiple LTM4637 devices can be paralleled to provide more output current without increasing input and output ripple voltage. The MODE_PLLIN pin allows the LTM4637 to be synchronized to an external clock and the internal phase-locked loop allows the LTM4637 to lock onto input clock phase as well. The fSET resistor is selected for nor- mal frequency, then the incoming clock can synchronize the device over the specified range. See Figure 24 for a synchronizing example circuit. A multiphase power supply significantly reduces the amount of ripple current in both the input and output ca- pacitors. The RMS input ripple current is reduced by, and the effective ripple frequency is multiplied by, the number of phases used (assuming that the input voltage is greater than the number of phases used times the output voltage). The output ripple amplitude is also reduced by the number of phases used. See Application Note 77. The LTM4637 device is an inherently current mode con- trolled device, so parallel modules will have good current sharing. This will balance the thermals in the design. Tie the COMP and VFB pins of each LTM4637 together to share the current evenly. Figure 24 shows a schematic of the parallel design. APPLICATIONS INFORMATION
Figure 3. Relationship Between Switching Figure 2. Normalized Input RMS Ripple Current vs Duty Cycle for One to Six µModule Regulators (Phases)
4637 F02
1 PHASE
2 PHASE
3 PHASE
4 PHASE
6 PHASE
point. Limit 5V output to 15A.
Figure 5. Output Voltage Coincident T racking Characteristics Figure 4. Dual Outputs (1.5V and 1.2V) with Tracking
4637 F04
composite diode voltage slope. remove the IS dependency from the following equation. a zero intercept at 0 Kelvin. used to monitor the internal temperature of the LTM4637. at a 10:1 ratio. See Figure 22 for an example.
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Figure 6. Diode Voltage VD vs Temperature
For more information www.linear .com/L TM4637 APPLICATIONS INFORMATION Overtemperature Protection The internal overtemperature protection monitors the internal temperature of the module and shuts off the regulator at ~130°C to 137°C. Once the regulator cools down the regulator will restart. Run Enable The RUN pin is used to enable the power module or se- quence the power module. The threshold is 1.25V, and the pin has an internal 5.1V Zener to protect the pin. The RUN pin can be used as an undervoltage lockout (UVLO) function by connecting a resistor divider from the input supply to the RUN pin: VUVLO = ((R1+R2)/R2) • 1.25V See Figure 1, Simplified Block Diagram. INTVCC Regulator The LTM4637 has an internal low dropout regulator from VIN called INTVCC. This regulator output has a 2.2µF ceramic capacitor internal. An additional 2.2µF ceramic capacitor is needed on this pin to ground. This regulator powers the internal controller and MOSFET drivers. The gate driver current is ~20mA for 750kHz operation. The regulator loss can be calculated as: (VIN – 5V) • 20mA = PLOSS EXTVCC external voltage source ≥ 4.7V can be applied to this pin to eliminate the internal INTVCC LDO power loss and increase regulator efficiency. A 5V supply can be applied to run the internal circuitry and power MOSFET driver. If unused, leave pin floating. EXTV CC must be less than VIN at all times during power-on and power-off sequences. Stability Compensation The LTM4637 has already been internally compensated for all output voltages. Table 5 is provided for most ap- plication requirements. L TpowerCAD is available for other control loop optimization. Thermal Considerations and Output Current Derating The thermal resistances reported in the Pin Configuration section of the data sheet are consistent with those param- eters defined by JESD51-12 and are intended for use with finite element analysis (FEA) software modeling tools that leverage the outcome of thermal modeling, simulation, and correlation to hardware evaluation performed on a µModule package mounted to a hardware test board. The motivation for providing these thermal coefficients in found in JESD 51-12 (“Guidelines for Reporting and Using Electronic Package Thermal Information”). Many designers may opt to use laboratory equipment and a test vehicle such as the demo board to predict the µModule regulator’s thermal performance in their appli- cation at various electrical and environmental operating conditions to compliment any FEA activities. Without FEA software, the thermal resistances reported in the Pin Con- figuration section are, in and of themselves, not relevant to providing guidance of thermal performance; instead, the derating curves provided in this data sheet can be used in a manner that yields insight and guidance pertaining to one’s application-usage, and can be adapted to correlate thermal performance to one’s own application. The Pin Configuration section gives four thermal coeffi- cients explicitly defined in JESD 51-12; these coefficients are quoted or paraphrased below: 1 θJA, the thermal resistance from junction to ambient, is the natural convection junction-to-ambient air thermal resistance measured in a one cubic foot sealed enclo- sure. 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 95mm × 76mm PCB with four layers. 2 θJCbottom, the thermal resistance from junction to the bottom of the product case, is determined 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 pack- age, 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.
the heat flows from the junction to the top of the part. generally match the user’s application. a specified distance from the package. resistances are external to the µModule package. airflow, a majority of the heat flow is into the board. Figure 7. Graphical Representation of JESD 51-12 Thermal Coefficients
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Figure 8. 1VOUT Power Loss Figure 9. 2.5VOUT Power Loss Figure 10. 5VOUT Power Loss yields the set of derating curves shown in this data sheet. multiplicative factors according to the ambient temperature. ambient temperature is increased with and without airflow. current or power with increasing ambient temperature. module loss as ambient temperature is increased .
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Figure 11. 5VIN to 1.0VOUT No Heat Sink Figure 14. 12VIN to 1.0VOUT with Heat Sink Figure 15. 5VIN to 2.5VOUT No Heat Sink Figure 13. 12VIN to 1.0VOUT No Heat SinkFigure 12. 5VIN to 1.0VOUT with Heat Sink Figure 16. 5VIN to 2.5VOUT with Heat Sink Figure 17. 12VIN to 2.5VOUT No Heat Sink Figure 18. 12VIN to 2.5VOUT with Heat Sink
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0 LFM
200 LFM
400 LFM
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Table 2. 1V Output Table 3. 2.5V Output Table 4. 5V Output (5V Output Connected to EXTV CC Pin) Figure 19. 12VIN to 5VOUT No Heat Sink, EXTVCC = 5V Figure 20. 12VIN to 5VOUT with Heat Sink, EXTVCC = 5V
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Table 5. Output Voltage Response vs Component Matrix (Refer to Figure 22) 0A to 10A Load Step †Bulk capacitance is optional if VIN has very low input impedance.
to be provided to protect each unit from catastrophic failure. protection and overtemperature protection. considerations are still necessary.
- Use large PCB copper areas for high current paths, including VIN, GND and VOUT. It helps to minimize the PCB conduction loss and thermal stress.
- Place high frequency ceramic input and output capacitors next to the VIN, GND and VOUT pins to minimize high frequency noise.
- Place a dedicated power ground layer underneath the unit.
- To minimize the via conduction loss and reduce module thermal stress, use multiple vias for interconnection between top layer and other power layers.
- Do not put vias directly on the pad, unless they are capped or plated over.
- Place test points on signal pins for testing.
- Use a separated SGND ground copper area for components connected to signal pins. Connect the SGND to GND underneath the unit.
- For parallel modules, tie the COMP and VFB pins together. Use an internal layer to closely connect these pins together. Figure 21 gives a good example of the recommended layout.
Table 6. Recommended Heat Sinks
Figure 21. Recommended PCB Layout Figure 22. 4.5V to 20VIN, 1.5V at 20A Design
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Figure 23. 3.3V at 40A, Two Parallel Outputs with 2-Phase Operation
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Figure 24. 1.2V, 80A, Current Sharing with 4-Phase Operation
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For more information www.linear .com/L TM4637 PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION A1 VIN B1 VIN C1 VIN D1 GND E1 GND F1 GND A2 VIN B2 VIN C2 VIN D2 GND E2 GND F2 GND A3 VIN B3 VIN C3 VIN D3 GND E3 GND F3 GND A4 VIN B4 VIN C4 VIN D4 GND E4 GND F4 GND A5 VIN B5 VIN C5 VIN D5 GND E5 GND F5 GND A6 VIN B6 VIN C6 VIN D6 GND E6 GND F6 GND A7 INTVCC B7 GND C7 GND D7 – E7 GND F7 GND A8 MODE_PLLIN B8 – C8 – D8 GND E8 – F8 GND A9 TRACK/SS B9 GND C9 GND D9 INTVCC E9 GND F9 GND A10 RUN B10 – C10 MTP3 D10 TEMP E10 – F10 – A11 COMP B11 MTP2 C11 MTP4 D11 MTP6 E11 – F11 PGOOD A12 MTP1 B12 fSET C12 MTP5 D12 MTP7 E12 EXTVCC F12 VFB PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION PIN ID FUNCTION G1 GND H1 GND J1 VOUT K1 VOUT L1 VOUT M1 VOUT G2 GND H2 GND J2 VOUT K2 VOUT L2 VOUT M2 VOUT G3 GND H3 GND J3 VOUT K3 VOUT L3 VOUT M3 VOUT G4 GND H4 GND J4 VOUT K4 VOUT L4 VOUT M4 VOUT G5 GND H5 GND J5 VOUT K5 VOUT L5 VOUT M5 VOUT G6 GND H6 GND J6 VOUT K6 VOUT L6 VOUT M6 VOUT G7 GND H7 GND J7 VOUT K7 VOUT L7 VOUT M7 VOUT G8 GND H8 GND J8 VOUT K8 VOUT L8 VOUT M8 VOUT G9 GND H9 GND J9 VOUT K9 VOUT L9 VOUT M9 VOUT G10 – H10 – J10 VOUT K10 VOUT L10 VOUT M10 VOUT G11 SGND H11 SGND J11 – K11 VOUT L11 VOUT M11 VOUT G12 PGOOD H12 SGND J12 VOSNS+ K12 DIFF_OUT L12 VOUT_LCL M12 VOSNS– PACKAGE DESCRIPTION Pin Assignment Table (Arranged by Pin Number) PACKAGE PHOTO PACKAGE ROW AND COLUMN LABELING MAY VARY AMONG µModule PRODUCTS. REVIEW EACH PACKAGE LAYOUT CAREFULL Y.
For more information www.linear .com/L TM4637 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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 2. ALL DIMENSIONS ARE IN MILLIMETERS LAND DESIGNATION PER JESD MO-222, SPP-010 5. PRIMARY DATUM -Z- IS SEATING PLANE 6. THE TOTAL NUMBER OF PADS: 133 DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PAD #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE SYMBOL aaa bbb eee TOLERANCE 0.15 0.10 0.05 4.22 – 4.42 DETAIL B DETAIL B SUBSTRATE MOLD CAP 0.27 – 0.37 3.95 – 4.05 bbb Z Z BSC 8.42 BSC 3.29 BSC PACKAGE TOP VIEW BSC 3.54 BSC 2.18 BSC PAD 1 CORNER X Y aaa Z aaa Z DETAIL A 13.97 BSC 1.27 BSC 13.97 BSC 0.12 – 0.28 L K J H G F E D C B PACKAGE BOTTOM VIEW C(0.30) PAD 1 PADS SEE NOTES M A DETAIL A 0.630 ±0.025 SQ. 133x S Y X eee SUGGESTED PCB LAYOUT TOP VIEW 0.0000 0.6350 0.6350 1.9050 1.9050 3.1750 3.1750 4.4450 4.4450 5.7150 5.7150 6.9850 6.9850 6.9850 5.7150 5.7150 4.4450 4.4450 3.1750 3.1750 1.9050 1.9050 0.6350 0.6350 0.0000 6.9850 LGA 133 0811 REV Ø L TMXXXXXX µModule TRAY PIN 1 BEVEL PACKAGE IN TRAY LOADING ORIENTATION COMPONENT PIN “A1” 0.630 0.630 133-Lead (15mm × 15mm × 4.32mm) (Reference LTC DWG # 05-08-1906 Rev Ø)
For more information www.linear .com/L TM4637 LINEAR TECHNOLOGY CORPORATION 2013 LT 0413 • PRINTED IN USA Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com/L TM4637 RELATED PARTS DESIGN RESOURCES TYPICAL APPLICATION PART NUMBER DESCRIPTION COMMENTS LTM4609 Buck-Boost DC/DC µModule Family All Pin Compatible; Up to 5A; Up to 36VIN, 34VOUT 15mm × 15mm × 2.82mm LTM4612 Ultralow Noise High VOUT DC/DC µModule Regulator 5A, 5V ≤ VIN ≤ 36V, 3.3V ≤ VOUT ≤ 15V, 15mm × 15mm × 2.82mm Package LTM4627 15A DC/DC µModule Regulator 4.5V ≤ VIN ≤ 20V, 0.6V ≤ VOUT ≤ 5V, LGA and BGA Packages LTM4620 Dual 13A, Single 26A DC/DC µModule Regulator Up to 100A with Four in Parallel, 4.5V ≤ VIN ≤ 16V, 0.6V ≤ VOUT ≤ 2.5V COMP TRACK/SS RUN f SET MODE_PLLIN TEMP PGOOD V OUT VOUT_LCL DIFF_OUT VOSNS+ VOSNS– VFB LTM4637 VIN 10k RFB 30.1k 75k CIN 22µF 25V ×4 C7 0.1µF 100µF 6.3V X5R 470µF V OUT 1.8V 20A INTV CCEXTVCC CONTINUOUS MODE
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1.8V at 20A Design SUBJECT DESCRIPTION µModule Design and Manufacturing Resources Design:
- Selector Guides
- Demo Boards and Gerber Files
- Free Simulation Tools Manufacturing:
- Quick Start Guide
- PCB Design, Assembly and Manufacturing Guidelines
- Package and Board Level Reliability µModule Regulator Products Search 1. Sort table of products by parameters and download the result as a spread sheet. 2. Search using the Quick Power Search parametric table. TechClip Videos Quick videos detailing how to bench test electrical and thermal performance of µModule products. Digital Power System Management Linear Technology’s family of digital power supply management ICs are highly integrated solutions that offer essential functions, including power supply monitoring, supervision, margining and sequencing, and feature EEPROM for storing user configurations and fault logging.