LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 High-Voltage 1-A Step-Down Switching Regulator Check for Samples: LM5010 FEATURES APPLICATIONS * * * * * * * * * * 1 2 * * * * * Input Voltage Range: 8V to 75V Valley Current Limit At 1.25A Switching Frequency Can Exceed 1 MHz Integrated N-Channel Buck Switch Integrated Startup Regulator No Loop Compensation Required Ultra-Fast Transient Response Operating Frequency Remains Constant With Load and Line Variations Maximum Duty Cycle Limited During Startup Adjustable Output Voltage Precision 2.5V Feedback Reference Thermal shutdown Packages - 10-Pin WSON (4 mm x 4 mm) - 14-Pin HTSSOP - Both Packages Have Exposed Thermal Pad For Improved Heat Dissipation High Efficiency Point-Of-Load (POL) Regulator Non-Isolated Telecommunications Buck Regulator Secondary High Voltage Post Regulator Automotive Systems * * DESCRIPTION The LM5010 Step Down Switching Regulator features all the functions needed to implement a low cost, efficient, buck bias regulator capable of supplying in excess of 1A load current. This high voltage regulator contains an N-Channel Buck Switch, and is available in thermally enhanced 10-pin WSON and 14-pin HTSSOP packages. The hysteretic regulation scheme requires no loop compensation, results in fast load transient response, and simplifies circuit implementation. The operating frequency remains constant with line and load variations due to the inverse relationship between the input voltage and the on-time. The valley current limit detection is set at 1.25A. Additional features include: VCC under-voltage lockout, thermal shutdown, gate drive under-voltage lockout, and maximum duty cycle limiter. DEVICE INFORMATION 8V - 75V Input VCC VIN C3 C1 LM5010 RON BST C4 L1 RON / SD SHUTDOWN VOUT SW D1 SS R1 ISEN C2 C6 FB RTN SGND R2 Figure 1. Basic Step-Down Regulator 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2004-2013, Texas Instruments Incorporated LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com Connection Diagram Top View Top View 1 2 3 4 5 SW VIN BST VCC I SEN R ON /SD S GND SS RTN FB 10 1 9 2 8 3 14 NC NC SW VIN BST VCC 7 4 I SEN R ON /SD 6 5 6 10 Lead WSON 7 S GND SS RTN FB NC NC 13 12 11 10 9 8 14 Lead HTSSOP Pin Functions Table 1. Pin Description PIN NUMBER 2 NAME DESCRIPTION APPLICATION INFORMATION WSON10 HTSSOP14 1 2 SW Switching Node Internally connected to the buck switch source. Connect to the inductor, free-wheeling diode, and bootstrap capacitor. 2 3 BST Boost pin for bootstrap capacitor Connect a 0.022 F capacitor from SW to this pin. The capacitor is charged from VCC via an internal diode during each off-time. 3 4 ISEN Current sense The re-circulating current flows through the internal sense resistor, and out of this pin to the free-wheeling diode. Current limit is nominally set at 1.25A. 4 5 SGND Sense Ground Re-circulating current flows into this pin to the current sense resistor. 5 6 RTN Circuit Ground Ground for all internal circuitry other than the current limit detection. 6 9 FB Feedback input from the regulated output Internally connected to the regulation and over-voltage comparators. The regulation level is 2.5V. 7 10 SS Softstart An internal 11.5 A current source charges an external capacitor to 2.5V, providing the soft start function. 8 11 RON/SD On-time control and shutdown An external resistor from VIN to this pin sets the buck switch ontime. Grounding this pin shuts down the regulator. 9 12 VCC Output from the startup regulator Nominally regulates at 7.0V. An external voltage (7.5V-14V) can be applied to this pin to reduce internal dissipation. An internal diode connects VCC to VIN. 10 13 VIN Input supply voltage Nominal input range is 8.0V to 75V. 1, 7, 8, 14 NC No connection No internal connection. Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) VIN to GND 76V BST to GND 90V SW to GND (Steady State) -1.5V BST to VCC 76V BST to SW 14V VCC to GND 14V SGND to RTN -0.3V to +0.3V SS to RTN -0.3V to 4V VIN to SW 76V Current Out of ISEN See Text All Other Inputs to GND -0.3 to 7V ESD Rating, Human Body Model (2) 2kV Storage Temperature Range -55C to +150C Lead Temperature (Soldering 4 sec) (1) (2) (3) (3) 260C Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is intended to be functional. For specifications and test conditions, see the Electrical Characteristics. The human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin. For detailed information on soldering plastic HTSSOP and WSON packages, refer to the Packaging Data Book. Operating Ratings (1) VIN 8V to 75V -40C to + 125C Operating Junction Temperature (1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is intended to be functional. For specifications and test conditions, see the Electrical Characteristics. Electrical Characteristics Specifications with standard typeface are for TJ = 25C, and those with boldface type apply over full Operating Junction Temperature range. VIN = 48V, RON = 200k, unless otherwise stated (1) and (2). Symbol Parameter Test Conditions Min Typ Max Unit 6.6 7 7.4 Volts VCC Regulator VCCReg VCC regulated output VIN - VCC ICC = 0 mA, FS < 200 kHz, 7.5V VIN 8.0V 1.3 V VCC output impedance (0 mA ICC 5 mA) VIN = 8.0V 140 VIN = 48V 2.5 VCC current limit (3) VCC = 0V 10 VCC increasing 5.8 V UVLOVCC hysteresis VCC decreasing 145 mV UVLOVCC filter delay 100 mV overdrive IIN operating current Non-switching, FB = 3V 650 850 A IIN shutdown current RON/SD = 0V 95 200 A UVLOVCC VCC under-voltage lockout threshold (1) (2) (3) mA 3 s Typical specifications represent the most likely parametric norm at 25C operation. All electrical characteristics having room temperature limits are tested during production with TA = 25C. All hot and cold limits are specified by correlating the electrical characteristics to process and temperature variations and applying statistical process control. VCC provides bias for the internal gate drive and control circuits. Device thermal limitations limit external loading. Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 3 LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com Electrical Characteristics (continued) Specifications with standard typeface are for TJ = 25C, and those with boldface type apply over full Operating Junction Temperature range. VIN = 48V, RON = 200k, unless otherwise stated (1) and (2). Symbol Parameter Test Conditions Min Typ Max Unit 0.35 0.80 4.3 5.0 Switch Characteristics Rds(on) Buck Switch Rds(on) ITEST = 200 mA UVLOGD Gate Drive UVLO VBST - VSW Increasing 3.0 UVLOGD hysteresis 440 V mV Softstart Pin Pull-up voltage 2.5 V Internal current source 11.5 A Current Limit ILIM Threshold Current out of ISEN 1 1.25 1.5 A Resistance from ISEN to SGND 130 m Response time 150 ns On Timer, RON/SD Pin tON - 1 On-time VIN = 10V, RON = 200 k 2.1 2.75 3.4 s tON - 2 On-time VIN = 75V, RON = 200 k 290 390 490 ns Shutdown threshold Voltage at RON/SD rising 0.35 0.65 1.1 V Threshold hysteresis Voltage at RON/SD falling 40 mV 265 ns Off Timer tOFF Off-time Regulation and Over-Voltage Comparators (FB Pin) VREF FB regulation threshold SS pin = steady state FB over-voltage threshold 2.445 2.5 2.550 V 2.9 V 1 nA Thermal shutdown temperature 175 C Thermal shutdown hysteresis 20 C FB bias current Thermal Shutdown TSD Thermal Resistance JA 4 Junction to Ambient WSON-10 Package 40 HTSSOP-14 Package 40 Submit Documentation Feedback C/W Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 TYPICAL APPLICATION CIRCUIT AND BLOCK DIAGRAM INPUT 10 LM5010 7V START-UP REGULATOR VIN C5 VCC UVLO VCC 9 Thermal Shutdown C3 C1 RON ON TIMER 8 R ON /SD 7 RON START COMPLETE 2.5V 11.5 PA SS 265 ns OFF TIMER 0.7V START COMPLETE VIN C4 DRIVER LOGIC Driver C6 6 FB BST 2 Gate Drive UVLO LEVEL SHIFT L1 OVER-VOLTAGE COMPARATOR REGULATION COMPARATOR D1 CURRENT LIMIT COMPARATOR 62.5 mV 5 RTN VOUT1 SW 1 2.9V ISEN + 3 R SENSE 50 m: SGND R1 RCL 4 R2 R3 VOUT2 C2 GND NOTE: Pin numbers are for the WSON-10 package. Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 5 LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com Typical Performance Characteristics 7.5 8 VIN = 48V 7 7.0 6 FS = 100 kHz FS = 620 kHz VIN = 8V 5 VCC (V) VCC (V) 6.5 6.0 VIN = 9V 4 FS = 200 kHz 3 2 5.5 VCC Externally Loaded Load Current = 300 mA ICC = 0 mA 1 FS = 100 kHz 5.0 0 6.5 7.0 7.5 8.0 8.5 9.0 10 9.5 0 2 4 VIN (V) 10 Figure 3. VCC vs ICC 9 8.0 8 7.0 FS = 550 kHz RON = 500k 7 6.0 6 ON-TIME (Ps) ICC INPUT CURRENT(mA) 8 ICC (mA) Figure 2. VCC vs VIN 5.0 4.0 FS = 200 kHz 3.0 300k 5 4 3 2.0 100k 2 FS = 100 kHz 1.0 1 0 0 8 7 9 10 11 12 13 14 0 8 20 EXTERNALLY APPLIED VCC (V) 40 60 80 VIN (V) Figure 4. ICC vs Externally Applied VCC Figure 5. On-Time vs VIN and RON 4.0 800 FB = 3V 700 RON = 50k 600 3.0 115k 500 IIN (PA) RON/SD PIN VOLTAGE (V) 6 301k 2.0 400 300 511k 200 1.0 RON/SD = 0V 100 0 0 0 8 20 40 60 80 8 20 40 60 80 VIN (V) VIN (V) Figure 6. Voltage at RON/SD Pin 6 0 Figure 7. IIN vs VIN Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 Typical Performance Characteristics (continued) VIN 7.0V UVLO VCC SW Pin Inductor Current 2.5V SS Pin VOUT t2 t1 Figure 8. Startup Sequence FUNCTIONAL DESCRIPTION The LM5010 Step Down Switching Regulator features all the functions needed to implement a low cost, efficient buck bias power converter capable of supplying in excess of 1A to the load. This high voltage regulator contains an N-Channel buck switch, is easy to implement, and is available in the thermally enhanced WSON-10 and HTSSOP-14 packages. The regulator's operation is based on a hysteretic control scheme, and uses an on-time which varies inversely with VIN. This feature results in the operating frequency remaining relatively constant with load and input voltage variations. The switching frequency can range from 100 kHz to > 1.0 MHz. The hysteretic control requires no loop compensation resulting in very fast load transient response. The valley current limit detection circuit, internally set at 1.25A, holds the buck switch off until the high current level subsides. Typical Application Circuit and Block Diagram shows the functional block diagram. The LM5010 can be applied in numerous applications to efficiently regulate down higher voltages. This regulator is well suited for 48V telecom applications, as well as the new 42V automotive power bus. Implemented as a Point-of-Load regulator following a highly efficient intermediate bus converter can result in high overall system efficiency. Features include: Thermal shutdown, VCC under-voltage lockout, gate drive under-voltage lockout, and maximum duty cycle limit. Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 7 LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com Hysteretic Control Circuit Overview The LM5010 buck DC-DC regulator employs a control scheme based on a comparator and a one-shot on-timer, with the output voltage feedback (FB) compared to an internal reference (2.5V). If the FB voltage is below the reference the buck switch is turned on for a time period determined by the input voltage and a programming resistor (RON). Following the on-time the switch remains off for 265 ns, or until the FB voltage falls below the reference, whichever is longer. The buck switch then turns on for another on-time period. Typically when the load current increases suddenly, the off-times are temporarily at the minimum of 265 ns. Once regulation is established, the off-time resumes its normal value. The output voltage is set by two external resistors (R1, R2). The regulated output voltage is calculated as follows: VOUT = 2.5V x (R1 + R2) / R2 (1) Output voltage regulation is based on ripple voltage at the feedback input, requiring a minimum amount of ESR for the output capacitor C2. The LM5010 requires a minimum of 25 mV of ripple voltage at the FB pin. In cases where the capacitor's ESR is insufficient additional series resistance may be required (R3 in Typical Application Circuit and Block Diagram). When in regulation, the LM5010 operates in continuous conduction mode at heavy load currents and discontinuous conduction mode at light load currents. In continuous conduction mode current always flows through the inductor, never reaching zero during the off-time. In this mode the operating frequency remains relatively constant with load and line variations. The minimum load current for continuous conduction mode is one-half the inductor's ripple current amplitude. The approximate operating frequency is calculated as follows: VOUT FS = 1.18 x 10-10 x RON (2) The buck switch duty cycle is approximately equal to: VOUT tON DC = tON + tOFF = VIN (3) At low load current, the circuit operates in discontinuous conduction mode, during which the inductor current ramps up from zero to a peak during the on-time, then ramps back to zero before the end of the off-time. The next on-time period starts when the voltage at FB falls below the reference - until then the inductor current remains zero, and the load current is supplied by the output capacitor (C2). In this mode the operating frequency is lower than in continuous conduction mode, and varies with load current. Conversion efficiency is maintained at light loads since the switching losses reduce with the reduction in load and frequency. The approximate discontinuous operating frequency can be calculated as follows: VOUT2 x L1 x 1.4 x 1020 FS = RL x (RON)2 (4) where RL = the load resistance. For applications where lower output voltage ripple is required the output can be taken directly from a low ESR output capacitor as shown in Figure 9. However, R3 slightly degrades the load regulation. L1 SW LM5010 R1 R3 FB V OUT2 R2 C2 Figure 9. Low Ripple Output Configuration 8 Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 Start-up Regulator (VCC) The startup regulator is integral to the LM5010. The input pin (VIN) can be connected directly to line voltages up to 75V. The VCC output is regulated at 7.0V, 6%, and is current limited to 10 mA. Upon power up the regulator sources current into the external capacitor at VCC (C3). With a 0.1 F capacitor at VCC, approximately 58 s are required for the VCC voltage to reach the under-voltage lockout threshold (UVLO) of 5.8V (t1 in Figure 8), at which time the buck switch is enabled, and the soft start pin is released to allow the soft start capacitor (C6) to charge up. VOUT then increases to its regulated value as the soft start voltage increases (t2 in Figure 8). The minimum input operating voltage is determined by the regulator's dropout voltage, the VCC UVLO falling threshold (5.65V), and the frequency. When VCC falls below the falling threshold the VCC UVLO activates to shut off the buck switch and ground the soft start pin. If VCC is externally loaded, the minimum input voltage increases since the output impedance at VCC is 140 at low VIN. See Figure 2 and Figure 3. In applications involving a high value for VIN where power dissipation in the startup regulator is a concern, an auxiliary voltage can be diode connected to the VCC pin (Figure 10). Setting the auxiliary voltage to between 7.5V and 14V shuts off the internal regulator, reducing internal power dissipation. The current required into the VCC pin is shown in Figure 4. Internally a diode connects VCC to VIN. VCC C3 BST C4 LM5010 L1 D2 SW VOUT1 D1 I SEN R1 R3 V OUT2 S GND R2 C2 FB Figure 10. Self Biased Configuration Regulation Comparator The feedback voltage at FB is compared to the voltage at the Softstart pin (2.5V, 2%). In normal operation (the output voltage is regulated) an on-time period is initiated when the voltage at FB falls below 2.5V. The buck switch stays on for the on-time causing the FB voltage to rise above 2.5V. After the on-time period the buck switch stays off until the FB voltage falls below 2.5V. Bias current at the FB pin is less than 5 nA over temperature. Over-Voltage Comparator The feedback voltage at FB is compared to an internal 2.9V reference. If the voltage at FB rises above 2.9V the on-time is immediately terminated. This condition can occur if the input voltage, or the output load, change suddenly. The buck switch will not turn on again until the voltage at FB falls below 2.5V. ON-Time Control The on-time of the internal switch (see Figure 5) is determined by the RON resistor and the input voltage (VIN), calculated from the following: 1.18 x 10-10 x (RON + 1.4k) tON = VIN - 1.4V + 67 ns (5) Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 9 LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com The inverse relationship of tON vs. VIN results in a nearly constant frequency as VIN is varied. If the application requires a high frequency the minimum value for tON, and consequently RON, is limited by the off-time (265 ns, 15%) which limits the maximum duty cycle at minimum VIN. The tolerance for Equation 5 is 25%. Frequencies in excess of 1 MHz are possible with the LM5010. Shutdown The LM5010 can be remotely shut down by taking the RON/SD pin below 0.65V. See Figure 11. In this mode the soft start pin is internally grounded, the on-timer is disabled, and the input current at VIN is reduced (Figure 7). Releasing the RON/SD pin allows normal operation to resume. When the switch is open, the nominal voltage at RON/SD is shown in Figure 6. VIN Input Voltage RON LM5010 R ON /SD STOP RUN Figure 11. Shutdown Implementation Current Limit Current limit detection occurs during the off-time by monitoring the recirculating current through the free-wheeling diode (D1). The detection threshold is 1.25A, 0.25A. Referring to Typical Application Circuit and Block Diagram, when the buck switch is off the inductor current flows through the load, into SGND, through the sense resistor, out of ISEN and through D1. If that current exceeds the threshold the current limit comparator output switches to delay the start of the next on-time period. The next on-time starts when the current out of ISEN is below the threshold and the voltage at FB is below 2.5V. If the overload condition persists causing the inductor current to exceed the threshold during each on-time, that is detected at the beginning of each off-time. The operating frequency is lower due to longer-than-normal off-times. Figure 12 illustrates the inductor current waveform. During normal operation the load current is IO, the average of the ripple waveform. When the load resistance decreases the current ratchets up until the lower peak attempts to exceed the threshold. During the Current Limited portion of Figure 12, the current ramps down to the threshold during each off-time, initiating the next on-time (assuming the voltage at FB is < 2.5V). During each on-time the current ramps up an amount equal to: 'I = (VIN - VOUT) x tON L1 (6) During this time the LM5010 is in a constant current mode, with an average load current (IOCL) equal to the threshold + I/2. The "valley current limit" technique allows the load current to exceed the current limit threshold as long as the lower peak of the inductor current is less than the threshold. 10 Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 IPK 'I IOCL Inductor Current Threshold IO Normal Operation Load Current Increases Current Limited Figure 12. Inductor Current - Current Limit Operation The current limit threshold can be increased by connecting an external resistor (RCL) between SGND and ISEN. The external resistor typically is less than 1, and its calculation is explained in the Applications Information section. The peak current out of SW and ISEN must not exceed 3.5A. The average current out of SW must be less than 3A, and the average current out of ISEN must be less than 2A. N-Channel Buck Switch and Driver The LM5010 integrates an N-Channel buck switch and associated floating high voltage gate driver. The peak current through the buck switch must not be allowed to exceed 3.5A, and the average current must be less than 3A. The gate driver circuit is powered by the external bootstrap capacitor between BST and SW (C4). During each off-time, the SW pin is at approximately -1V, and C4 is re-charged from VCC through the internal high voltage diode. The minimum off-time of 265 ns ensures a minimum time each cycle to recharge the bootstrap capacitor. A 0.022 F ceramic capacitor is recommended for C4. Soft Start The soft start feature allows the converter to gradually reach a steady state operating point, thereby reducing startup stresses and current surges. Upon turn-on, after VCC reaches the under-voltage threshold (t1 in Figure 8), an internal 11.5 A current source charges the external capacitor at the Softstart pin to 2.5V (t2 in Figure 8). The ramping voltage at SS (and at the non-inverting input of the regulation comparator) ramps up the output voltage in a controlled manner. This feature keeps the load current from going to current limit during startup, thereby reducing inrush currents. An internal switch grounds the Softstart pin if VCC is below the under-voltage lockout threshold, if a thermal shutdown occurs, or if the circuit is shutdown using the RON/SD pin. Thermal Shutdown The LM5010 should be operated so the junction temperature does not exceed 125C. If the junction temperature increases above that, an internal Thermal Shutdown circuit activates (typically) at 175C, taking the controller to a low power reset state by disabling the buck switch and the on-timer, and grounding the Softstart pin. This feature helps prevent catastrophic failures from accidental device overheating. When the junction temperature reduces below 155C (typical hysteresis = 20C), the Softstart pin is released and normal operation resumes. Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 11 LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com APPLICATIONS INFORMATION EXTERNAL COMPONENTS The procedure for calculating the external components is illustrated with a design example. The circuit in Typical Application Circuit and Block Diagram is to be configured for the following specifications: * VOUT = 10V * VIN = 15V to 75V * FS = 625 kHz * Minimum load current = 150 mA * Maximum load current = 1.0A * Softstart time = 5 ms R1 and R2: The ratio of these resistors is calculated from: R1/R2 = (VOUT/2.5V) - 1 (7) R1/R2 calculates to 3.0. The resistors should be chosen from standard value resistors in the range of 1.0 k - 10 k. Values of 3.0 k for R1, and 1.0 k for R2 will be used. RON, FS: RON sets the on-time, and can be chosen using Equation 2 to set a nominal frequency, or from Equation 5 if the on-time at a particular VIN is important. A higher frequency generally means a smaller inductor and capacitors (value, size and cost), but higher switching losses. A lower frequency means a higher efficiency, but with larger components. If PC board space is tight, a higher frequency is better. The resulting on-time and frequency have a 25% tolerance. Re-arranging Equation 2, RON = 10V 1.18 x 10-10 x 625 kHz = 136 k: (8) The next larger standard value (137 k) is chosen for RON, yielding a nominal frequency of 618 kHz. L1: The inductor value is determined based on the load current, ripple current, and the minimum and maximum input voltage (VIN(min), VIN(max)). Refer to Figure 13. IPK+ L1 Current IO IOR IPK- 0 mA 1/Fs Figure 13. Inductor Current To keep the circuit in continuous conduction mode, the maximum allowed ripple current is twice the minimum load current, or 300 mAp-p. Using this value of ripple current, the inductor (L1) is calculated using the following: VOUT1 x (VIN(max) - VOUT1) L1 = IOR x FS(min) x VIN(max) (9) where FS(min) is the minimum frequency (FS - 25%). 10V x (75V - 10V) L1 = 12 = 63 PH 0.30A x 463 kHz x 75V (10) Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 This provides a minimum value for L1 - the next higher standard value (100 H) will be used. L1 must be rated for the peak current (IPK+) to prevent saturation. The peak current occurs at maximum load current with maximum ripple. The maximum ripple is calculated by re-arranging Equation 9 using VIN(max), FS(min), and the minimum inductor value, based on the manufacturer's tolerance. Assume, for this exercise, the inductor's tolerance is 20%. VOUT1 x (VIN(max) - VOUT1) IOR(max) = L1MIN x FS(min) x VIN(max) (11) 10V x (75V - 10V) IOR(max) = 80 PH x 463 kHz x 75V = 234 mAp-p (12) (13) IPK+ = 1.0A + 0.234A / 2 = 1.117A RCL: Since it is obvious that the lower peak of the inductor current waveform does not exceed 1.0A at maximum load current (see Figure 13), it is not necessary to increase the current limit threshold. Therefore RCL is not needed for this exercise. For applications where the lower peak exceeds 1.0A, see the section below on increasing the current limit threshold. C2 and R3: Since the LM5010 requires a minimum of 25 mVp-p of ripple at the FB pin for proper operation, the required ripple at VOUT1 is increased by R1 and R2. This necessary ripple is created by the inductor ripple current acting on C2's ESR + R3. First, the minimum ripple current is determined. VOUT1 x (VIN(min) - VOUT1) IOR(min) = = L1MAX x FS(max) x VIN(min) 10V x (15V - 10V) 120 PH x 772 kHz x 15V = 36 mA (14) The minimum ESR for C2 is then equal to: ESR(min) = 25 mV x (R1 + R2) R2 x IOR(min) = 2.8: (15) If the capacitor used for C2 does not have sufficient ESR, R3 is added in series as shown in Typical Application Circuit and Block Diagram. C2 should generally be no smaller than 3.3 F, although that is dependent on the frequency and the allowable ripple amplitude at VOUT1. Experimentation is usually necessary to determine the minimum value for C2, as the nature of the load may require a larger value. A load which creates significant transients requires a larger value for C2 than a non-varying load. D1: The important parameters are reverse recovery time and forward voltage drop. The reverse recovery time determines how long the current surge lasts each time the buck switch is turned on. The forward voltage drop is significant in the event the output is short-circuited as it is mainly this diode's voltage (plus the voltage across the current limit sense resistor) which forces the inductor current to decrease during the off-time. For this reason, a higher voltage is better, although that affects efficiency. A reverse recovery time of 30 ns, and a forward voltage drop of 0.75V are preferred. The reverse leakage specification is important as that can significantly affect efficiency. Other types of diodes may have a lower forward voltage drop, but may have longer recovery times, or greater reverse leakage. D1 should be rated for the maximum VIN, and for the peak current when in current limit (IPK in Figure 11) which is equal to: IPK = 1.5A + IOR(max) = 1.734A (16) where 1.5A is the maximum guaranteed current limit threshold, and the maximum ripple current was previously calculated as 234 mAp-p. Note that this calculation is valid only when RCL is not required. C1: Assuming the voltage supply feeding VIN has a source impedance greater than zero, this capacitor limits the ripple voltage at VIN while supplying most of the switch current during the on-time. At maximum load current, when the buck switch turns on, the current into VIN increases to the lower peak of the output current waveform, ramps up to the peak value, then drops to zero at turn-off. The average current into VIN during this on-time is the load current. For a worst case calculation, C1 must supply this average load current during the maximum ontime. The maximum on-time is calculated using Equation 5, with a 25% tolerance added: Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 13 LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com 1.18 x 10-10 x (137k + 1.4k) x 1.25 tON(max) = 15V - 1.4V + 67 ns = 1.57 Ps (17) C1 is calculated from: C1 = IO x tON = 'V 1.0A x 1.57 Ps 1V = 1.57 PF (18) where IO is the load current, and V is the allowable ripple voltage at VIN (1V for this example). Quality ceramic capacitors with a low ESR should be used for C1. To allow for capacitor tolerances and voltage effects, a 2.2 F capacitor will be used C3: The capacitor at the VCC pin provides not only noise filtering and stability, but also prevents false triggering of the VCC UVLO at the buck switch on/off transitions. For this reason, C3 should be no smaller than 0.1 F, and should be a good quality, low ESR, ceramic capacitor. This capacitor also determines the initial startup delay (t1 in Figure 8). C4: The recommended value for C4 is 0.022 F. A high quality ceramic capacitor with low ESR is recommended as C4 supplies the surge current to charge the buck switch gate at turn-on. A low ESR also ensures a complete recharge during each off-time. C5: This capacitor suppresses transients and ringing due to long lead inductance at VIN. A low ESR, 0.1 F ceramic chip capacitor is recommended, located physically close to the LM5010. C6: The capacitor at the SS pin determines the soft start time, i.e. the time for the reference voltage at the regulation comparator, and the output voltage, to reach their final value. The time is determined from the following: tSS = C6 x 2.5V 11.5 PA (19) For a 5 ms soft start time, C6 calculates to 0.022 F. FINAL CIRCUIT The final circuit is shown in Figure 14, and its performance is shown in Figure 15 to Figure 18. VCC VIN 15 - 75V Input C1 2.2 PF C3 0.1 PF C5 0.1 PF BST RON 137k RON / SD LM5010 C4 0.022 PF L1 100 PH 10V SW SHUTDOWN VOUT D1 SS ISEN C6 0.022 PF SGND FB R1 3.0k R3 2.8 R2 1.0k C2 15 PF GND RTN Figure 14. LM5010 Example Circuit 14 Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 Table 2. Bill of Materials Item Description Part No. Package Value C1 Ceramic Capacitor TDK C4532X7R2A225M 1812 2.2 F, 100V C2 Ceramic Capacitor TDK C4532X7R1E156M 1812 15 F, 25V C3 Ceramic Capacitor Kemet C0805C104K4RAC 0805 0.1 F, 16V C4, C6 Ceramic Capacitor Kemet C0805C223K4RAC 0805 0.022 F, 16V C5 Ceramic Capacitor TDK C2012X7R2A104M 0805 0.1 F, 100V D1 Ultra fast diode Central Semi CMR2U-01 SMB 100V, 2A L1 Inductor TDK SLF10145 10.1 x 10.1 100 H R1 Resistor Vishay CRCW08053001F 0805 3.0 k R2 Resistor Vishay CRCW08051001F 0805 1.0 k R3 Resistor Vishay CRCW08052R80F 0805 2.8 RON Resistor Vishay CRCW08051373F 0805 137 k U1 Switching regulator LM5010 100 100 80 80 EFFICIENCY (%) EFFICIENCY (%) _ 60 40 20 VIN = 15V 60 24V 48V 75V 40 20 IOUT = 300mA 0 0 0 20 40 60 80 0 VIN (V) 200 400 600 800 _ 1000 LOAD CURRENT (mA) Figure 15. Efficiency vs VIN Circuit of Figure 14 Figure 16. Efficiency vs Load Current and VIN Circuit of Figure 14 700 350 600 250 FREQUENCY (kHz) OUTPUT RIPPLE (mVp-p) 300 200 150 100 500 400 50 0 300 0 20 40 60 80 VIN (V) 0 20 40 60 80 VIN (V) Figure 17. Output Voltage Ripple vs VIN Circuit of Figure 14 Figure 18. Frequency vs VIN Circuit of Figure 14 Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 15 LM5010 SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 www.ti.com INCREASING THE CURRENT LIMIT THRESHOLD The current limit threshold is nominally 1.25A, with a minimum guaranteed value of 1.0A. If, at maximum load current, the lower peak of the inductor current (IPK-in Figure 13) exceeds 1.0A, resistor RCL must be added between SGND and ISEN to increase the current limit threshold to equal or exceed that lower peak current. This resistor diverts some of the recirculating current from the internal sense resistor so that a higher current level is needed to switch the internal current limit comparator. IPK-is calculated from: IPK- = IO(max) - IOR(min) 2 (20) where IO(max) is the maximum load current, and IOR(min) is the minimum ripple current calculated using Equation 14. RCL is calculated from: RCL = 1.0A x 0.11: IPK- - 1.0A (21) where 0.11 is the minimum value of the internal resistance from SGND to ISEN. The next smaller standard value resistor should be used for RCL. With the addition of RCL it is necessary to check the average and peak current values to ensure they do not exceed the LM5010 limits. At maximum load current the average current through the internal sense resistor is: IO(max) x RCL x (VIN(max) - VOUT) IAVE = (RCL + 0.11: x VIN(max) (22) If IAVE is less than 2.0A no changes are necessary. If it exceeds 2.0A, RCL must be reduced. The upper peak of the inductor current (IPK+), at maximum load current, is calculated using the following: IOR(max) IPK+ = IO(max) + 2 (23) where IOR(max) is calculated using Equation 11. If IPK+ exceeds 3.5A , the inductor value must be increased to reduce the ripple amplitude. This will necessitate recalculation of IOR(min), IPK-, and RCL. When the circuit is in current limit, the upper peak current out of the SW pin is 1.5A x (150 m: + RCL) IPK+(CL) = RCL + IOR(MAX) (24) The inductor L1 and diode D1 must be rated for this current. PC BOARD LAYOUT The LM5010 regulation, over-voltage, and current limit comparators are very fast, and will respond to short duration noise pulses. Layout considerations are therefore critical for optimum performance. The layout must be as neat and compact as possible, and all the components must be as close as possible to their associated pins. The current loop formed by D1, L1, C2, and the SGND and ISEN pins should be as small as possible. The ground connection from C2 to C1 should be as short and direct as possible. If it is expected that the internal dissipation of the LM5010 will produce high junction temperatures during normal operation, good use of the PC board's ground plane can help considerably to dissipate heat. The exposed pad on the IC package bottom can be soldered to a ground plane, and that plane should both extend from beneath the IC, and be connected to exposed ground plane on the board's other side using as many vias as possible. The exposed pad is internally connected to the IC substrate. The use of wide PC board traces at the pins, where possible, can help conduct heat away from the IC. The four No Connect pins on the HTSSOP package are not electrically connected to any part of the IC, and may be connected to ground plane to help dissipate heat from the package. Judicious positioning of the PC board within the end product, along with the use of any available air flow (forced or natural convection) can help reduce the junction temperature. 16 Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 LM5010 www.ti.com SNVS307F - SEPTEMBER 2004 - REVISED FEBRUARY 2013 REVISION HISTORY Changes from Revision E (February 2013) to Revision F * Page Changed layout of National Data Sheet to TI format .......................................................................................................... 16 Submit Documentation Feedback Copyright (c) 2004-2013, Texas Instruments Incorporated Product Folder Links: LM5010 17 PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (C) Device Marking (4/5) LM5010MH NRND HTSSOP PWP 14 94 TBD Call TI Call TI -40 to 125 L5010 MH LM5010MH/NOPB ACTIVE HTSSOP PWP 14 94 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L5010 MH LM5010MHX/NOPB ACTIVE HTSSOP PWP 14 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L5010 MH LM5010SD/NOPB ACTIVE WSON DPR 10 1000 Green (RoHS & no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 L00057B LM5010SDX/NOPB ACTIVE WSON DPR 10 4500 Green (RoHS & no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 L00057B (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) LM5010MHX/NOPB HTSSOP PWP 14 2500 330.0 12.4 LM5010SD/NOPB WSON DPR 10 1000 178.0 LM5010SDX/NOPB WSON DPR 10 4500 330.0 6.95 8.3 1.6 8.0 12.0 Q1 12.4 4.3 4.3 1.3 8.0 12.0 Q1 12.4 4.3 4.3 1.3 8.0 12.0 Q1 Pack Materials-Page 1 W Pin1 (mm) Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM5010MHX/NOPB HTSSOP PWP 14 2500 367.0 367.0 35.0 LM5010SD/NOPB WSON DPR 10 1000 210.0 185.0 35.0 LM5010SDX/NOPB WSON DPR 10 4500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA PWP0014A MXA14A (Rev A) www.ti.com MECHANICAL DATA DPR0010A SDC10A (Rev A) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as "components") are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI's terms and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily performed. TI assumes no liability for applications assistance or the design of Buyers' products. Buyers are responsible for their products and applications using TI components. To minimize the risks associated with Buyers' products and applications, Buyers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications. In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI's goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. Nonetheless, such components are subject to these terms. No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use. Only those TI components which TI has specifically designated as military grade or "enhanced plastic" are designed and intended for use in military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of non-designated products, TI will not be responsible for any failure to meet ISO/TS16949. Products Applications Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP(R) Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com Wireless Connectivity www.ti.com/wirelessconnectivity Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2013, Texas Instruments Incorporated