LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 150-mA 100-V Step-Down Switching Regulator Check for Samples: LM5009 FEATURES DESCRIPTION * * * * * The LM5009 Step Down Switching Regulator features all of the functions needed to implement a low cost, efficient, Buck bias regulator. This device is capable of driving a 150 mA load current from a 9.5V to 95V input source. The switching frequency can exceed 600 kHz, depending on the input and output voltages. The output voltage may be set from 2.5V to 85V. This high voltage regulator contains an N-Channel buck switch and internal startup regulator. The device is easy to implement and is provided in the 8-pin VSSOP and the thermally enhanced 8-pin WSON packages. The LM5009 is a well suited alternative to a high voltage monolithic or discrete linear solution where the power loss becomes unacceptable. The regulator's operation is based on a control scheme using an ON time inversely proportional to VIN. This feature allows the operating frequency to remain relatively constant over load and input voltage variations. The control scheme requires no loop compensation, resulting in an ultra-fast transient response. An intelligent current limit is implemented with forced OFF time, which is inversely proportional to Vout. This scheme ensures short circuit protection while providing minimum foldback. Other features include: Thermal Shutdown, Vcc under-voltage lockout, Gate drive under-voltage lockout, and Maximum Duty Cycle limiter. 1 2 * * * * * * * * Integrated N-Channel MOSFET 150-mA output current capability Ultra-Fast Transient Response No loop compensation required Vin feed forward provides constant operating frequency Switching frequency can exceed 600 kHz Highly efficient operation 2% accurate 2.5V feedback from -40C to 125C Internal startup regulator Intelligent current limit protection External shutdown control Thermal shutdown 8-Pin VSSOP and thermally enhanced 8-Pin WSON packages APPLICATIONS * * * * * Heat sink eliminator for classic linear regulator applications 12V, 24V, 36V, and 48V rectified AC systems 42V Automotive Non-isolated AC mains charge coupled supplies LED Current Source Typical Application Circuit 9. 5 - 95V Input VIN VCC C3 LM5009 C1 BST R ON C4 RON/SD L1 SW VOUT SHUTDOWN D1 RCL R CL C2 R1 FB RTN 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) 2006-2013, Texas Instruments Incorporated LM5009 SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 www.ti.com Connection Diagram 1 8 SW VIN BST VCC RCL RON/SD RTN FB 2 3 7 6 4 5 Figure 2. 8-Lead VSSOP or WSON Pin Functions Table 1. Pin Descriptions Pin Name Description Application Information 1 SW Switching output Power switching output. Connect to the inductor, re-circulating diode, and bootstrap capacitor. 2 BST Boost Pin An external capacitor is required between the BST and the SW pins. A 0.022 F ceramic capacitor is recommended. An internal diode charges the capacitor from VCC. 3 RCL Current Limit off-time set pin A resistor between this pin and RTN sets the off-time when current limit is detected. The off-time is preset to 35s if FB = 0V. 4 RTN Ground pin Ground for the entire circuit. 5 FB Feedback input from Regulated Output This pin is connected to the inverting input of the internal regulation comparator. The regulation threshold is 2.5V. 6 RON/SD On-time set pin A resistor between this pin and VIN sets the switch on-time as a function of VIN. The minimum recommended on-time is 250ns at the maximum input voltage. This pin can be used for remote shutdown. 7 VCC Output from the internal high voltage startup regulator. Regulated at 7.0V. If an auxiliary voltage is available to raise the voltage on this pin above the regulation set point (7V), the internal series pass regulator will shutdown, reducing the IC power dissipation. Do not exceed 14V. This voltage provides gate drive power for the internal Buck switch. An internal diode is provided between this pin and the BST pin. A local 0.1F decoupling capacitor is required. 8 VIN Input voltage Recommended operating range: 9.5V to 95V. EP Exposed pad (WSON package only) Exposed metal pad on the underside of the device. It is recommended to connect this to the PC board ground plane to aid in heat dissipation. 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 RTN -0.3V to 100V BST to RTN -0.3V to 114V SW to RTN (Steady State) ESD Rating, Human Body Model -1V (2) 2kV BST to VCC 100V BST to SW 14V VCC to RTN 14V All Other Inputs to RTN -0.3 to 7V Storage Temperature Range (1) (2) 2 -65C to +150C 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. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 Operating Ratings (1) VIN 9.5V to 95V -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. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 3 LM5009 SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 www.ti.com Electrical Characteristics Limits in standard type are for TJ = 25C only, and limits in boldface type apply over the junction temperature (TJ) range of 40C to +125C. Minimum and Maximum limits are specified through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25C, and are provided for reference purposes only. Unless otherwise stated, the following conditions apply: VIN = 48V, RON = 200k. See (1) Symbol Parameter Conditions Min Typ Max 7 7.4 Unit VCC Supply VCC Reg VCC Regulator Output 6.6 V VCC Current Limit (2) 9.5 mA VCC undervoltage Lockout Voltage (VCC increasing) 6.3 V VCC Undervoltage Hysteresis 200 mV VCC UVLO Delay (filter) 100mV overdrive 10 IIN Operating Current Non-Switching, FB = 3V 485 675 A s IIN Shutdown Current RON/SD = 0V 76 150 A 2.0 4.4 4.5 5.5 Switch Characteristics Buck Switch Rds(on) ITEST = 200mA (3) Gate Drive UVLO VBST - VSW Rising 3.4 Gate Drive UVLO Hysteresis 430 V mV Current Limit Current Limit Threshold 0.25 Current Limit Response Time Iswitch Overdrive = 0.1A Time to Switch Off OFF time generator (test 1) FB=0V, RCL = 100K OFF time generator (test 2) FB=2.3V, RCL = 100K 0.31 0.37 A 400 ns 35 s 2.56 s On Time Generator TON - 1 Vin = 10V, Ron = 200K 2.15 TON - 2 Vin = 95V, Ron = 200K 200 Remote Shutdown Threshold Rising 0.40 Remote Shutdown Hysteresis 2.77 3.5 s 300 420 ns 0.70 1.05 V 35 mV 300 ns Minimum Off Time Minimum Off Timer FB = 0V Regulation and OV Comparators FB Reference Threshold Internal reference, Trip point for switch ON FB Over-Voltage Threshold Trip point for switch OFF 2.445 2.5 2.550 V 2.875 V 1 nA Thermal Shutdown Temperature 165 C Thermal Shutdown Hysteresis 25 C VSSOP Package 200 C/W WSON Package 40 C/W FB Bias Current Thermal Shutdown Tsd Thermal Resistance JA (1) (2) (3) 4 Junction to Ambient All electrical characteristics having room temperature limits are tested during production with TA = TJ = 25C. All hot and cold limits are specified by correlating the electrical characteristics to process and temperature variations and applying statistical process control. The VCC output is intended as a self bias for the internal gate drive power and control circuits. Device thermal limitations limit external loading. For devices procured in the WSON-8 package, the Rds(on) limits are specified by design characterization data only. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 Typical Performance Characteristics On-Time vs \ VIN and RON VCC vs VIN and FS 10 7.1 FS = 180 kHz 6.9 Ron = 500k VCC (V) ON-TIME (Ps) 7.0 1.0 400 kHz 6.8 725 kHz 300k 1.2 MHz 6.7 100k 6.6 0.1 20 40 60 80 6.5 9.0 100 9.5 10.0 VIN (V) Figure 3. Figure 4. Current Limit Off-Time vs VFB and RCL VCC vs ICC and VIN 35 8 30 7 VIN t 15V VIN = 9.5V 6 25 RCL = 500k 10V 5 20 15 11.0 10.5 VIN (V) VCC (V) CURRENT LIMIT OFF TIME (Ps) 0 4 3 300k 10 2 100k 5 1 50k 0 0 0 0.5 1.0 1.5 2.0 0 2.5 2 VFB (V) 4 6 8 10 ICC (mA, External Load) Figure 5. Figure 6. ICC Current vs Applied VCC Voltage 4.0 ICC INPUT CURRENT (mA) 3.5 FS = 1.2 MHz 3.0 FS = 725 kHz 2.5 FS = 400 kHz 2.0 1.5 1.0 FS = 180 kHz 0.5 0 8 9 10 11 12 13 14 EXTERNALLY APPLIED VCC (V) Figure 7. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 5 LM5009 SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 www.ti.com TYPICAL APPLICATION CIRCUIT AND BLOCK DIAGRAM 7V SERIES REGULATOR 9.5V - 95V Input LM5009 VCC 8 VIN C1 SD C5 C3 THERMAL SHUTDOWN UVLO ON TIMER START RON COMPLETE 6 SD/ RON BST Ron OVER-VOLTAGE COMPARATOR SHUTDOWN + - 2.875V START UVLO MINIMUM OFF-TIMER 5 FB FB 3 RCL S REGULATION COMPARATOR RCL R SET CLR L1 SW 1 VOUT1 Q Q R1 COMPLETE + - START CURRENT LIMIT OFF TIMER RCL C4 DRIVER LEVEL SHIFT + - 2 VIN SD COMPLETE 2.5V 4 7 0.31A BUCK SWITCH CURRENT SENSE R3 VOUT2 D1 RTN R2 C2 Figure 8. 6 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 FUNCTIONAL DESCRIPTION The LM5009 Step Down Switching Regulator features all the functions needed to implement a low cost, efficient, Buck bias power converter. This high voltage regulator contains a 100 V N-Channel Buck Switch, is easy to implement and is provided in the VSSOP-8 and the thermally enhanced WSON-8 packages. The regulator is based on a control scheme using an on-time inversely proportional to VIN. The control scheme requires no loop compensation. Current limit is implemented with forced off-time, which is inversely proportional to VOUT. This scheme ensures short circuit protection while providing minimum foldback. The Functional Block Diagram of the LM5009 is shown in Figure 8. The LM5009 can be applied in numerous applications to efficiently regulate down higher voltages. This regulator is well suited for 48 Volt Telecom and the 42V Automotive power bus ranges. Additional features include: Thermal Shutdown, VCC under-voltage lockout, Gate drive under-voltage lockout, Max Duty Cycle limit timer and the intelligent current limit off timer. Control Circuit Overview The LM5009 is a Buck DC-DC regulator that uses a control scheme in which the on-time varies inversely with line voltage (VIN). Control is based on a comparator and the on-time one-shot, with the output voltage feedback (FB) compared to an internal reference (2.5V). If the FB level is below the reference the buck switch is turned on for a fixed time determined by the line voltage and a programming resistor (RON). Following the ON period the switch will remain off for at least the minimum off-timer period of 300 ns. If FB is still below the reference at that time the switch will turn on again for another on-time period. This will continue until regulation is achieved, at which time the off-time increases based on the required duty cycle. The LM5009 operates in discontinuous conduction mode at light load currents, and continuous conduction mode at heavy load current. In discontinuous conduction mode, current through the output inductor starts at zero and ramps up 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 internal reference - until then the inductor current remains zero. In this mode the operating frequency is lower than in continuous conduction mode, and varies with load current. Therefore at light loads the conversion efficiency is maintained, since the switching losses reduce with the reduction in load and frequency. The discontinuous operating frequency can be calculated as follows: VOUT2 x L x 1.28 x 1020 F= RL x (RON)2 (1) where RL = the load resistance In continuous conduction mode, current flows continuously through the inductor and never ramps down to zero. In this mode the operating frequency is greater than the discontinuous mode frequency and remains relatively constant with load and line variations. The approximate continuous mode operating frequency can be calculated as follows: VOUT F= 1.25 x 10-10 x RON (2) The output voltage (VOUT) is programmed by two external resistors as shown in Figure 8. The regulation point is calculated as follows: VOUT = 2.5 x (R1 + R2) / R2 (3) This regulator regulates the output voltage based on ripple voltage at the feedback input, requiring a minimum amount of ESR for the output capacitor C2. A minimum of 25mV of ripple voltage at the feedback pin (FB) is required for the LM5009. In cases where the capacitor ESR is too small, additional series resistance may be required (R3 in Figure 8). 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. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 7 LM5009 SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 www.ti.com L1 SW LM5009 R1 R3 FB VOUT2 R2 C2 Figure 9. Low Ripple Output Configuration High Voltage Start-Up Regulator The LM5009 contains an internal high voltage startup regulator. The input pin (VIN) can be connected directly to line voltages up to 95 Volts, with transient capability to 100 volts. The regulator is internally current limited at 9.5mA. Upon power up, the regulator sources current into the external capacitor at VCC (C3). When the voltage on the VCC pin reaches the under-voltage lockout threshold of 6.3V, the buck switch is enabled. In applications involving a high value for VIN, where power dissipation in the VCC regulator is a concern, an auxiliary voltage can be diode connected to the VCC pin. Setting the voltage between 8V and 14V shuts off the internal regulator, reducing internal power dissipation. See Figure 10. The current required into the VCC pin is shown in the Typical Performance Characteristics. VCC C3 BST C4 LM5009 L1 D2 SW VOUT1 D1 R1 R3 R2 C2 FB Figure 10. Self-Biased Configuration Regulation Comparator The feedback voltage at FB is compared to an internal 2.5V reference. 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 will stay on for the programmed on-time, causing the FB voltage to rise above 2.5V. After the on-time period, the buck switch will stay off until the FB voltage again falls below 2.5V. During start-up, the FB voltage will be below 2.5V at the end of each on-time, resulting in the minimum off-time. Bias current at the FB pin is less than 5 nA over temperature. 8 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 Over-Voltage Comparator The feedback voltage at FB is compared to an internal 2.875V reference. If the voltage at FB rises above 2.875V the on-time pulse 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 Generator and Shutdown The on-time for the LM5009 is determined by the RON resistor, and is inversely proportional to the input voltage (Vin), resulting in a nearly constant frequency as Vin is varied over its range. The on-time equation is: TON = 1.25 x 10-10 x RON / VIN (4) RON should be selected for a minimum on-time (at maximum VIN) greater than 250 ns, for proper current limit operation. This requirement limits the maximum frequency for each application, depending on VIN and VOUT. The LM5009 can be remotely disabled by taking the RON/SD pin to ground. See Figure 11. The voltage at the RON/SD pin is between 1.7V and 5V, depending on Vin and the value of the RON resistor. Input Voltage VIN RON LM5009 RON/SD STOP RUN Figure 11. Shutdown Implementation Current Limit The LM5009 contains an intelligent current limit OFF timer. If the current in the Buck switch exceeds 0.31A the present cycle is immediately terminated, and a non-resetable OFF timer is initiated. The length of off-time is controlled by an external resistor (RCL) and the FB voltage. When FB = 0V, a maximum off-time is required, and the time is preset to 35s. This condition occurs when the output is shorted, and during the initial part of start-up. This amount of time ensures safe short circuit operation up to the maximum input voltage of 95V. In cases of overload where the FB voltage is above zero volts (not a short circuit) the current limit off-time will be less than 35s. Reducing the off-time during less severe overloads reduces the amount of foldback, recovery time, and the start-up time. The off-time is calculated from the following equation: 10 TOFF = 0.285 + -5 VFB -6 (6.35 x 10 x RCL) (5) The current limit sensing circuit is blanked for the first 50-70ns of each on-time so it is not falsely tripped by the current surge which occurs at turn-on. The current surge is required by the re-circulating diode (D1) for its turnoff recovery. N-Channel Buck Switch and Driver The LM5009 integrates an N-Channel buck switch and associated floating high voltage gate driver. The gate driver circuit works in conjunction with an external bootstrap capacitor and an internal high voltage diode. A 0.022F ceramic capacitor (C4) connected between the BST pin and SW pin provides the voltage to the driver during the on-time. During each off-time, the SW pin is at approximately -1V, and the bootstrap capacitor charges from Vcc through the internal diode. The minimum OFF timer ensures a minimum time each cycle to recharge the bootstrap capacitor. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 9 LM5009 SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 www.ti.com An external re-circulating diode (D1) carries the inductor current after the internal buck switch turns off. This diode should be of the ultra-fast or Schottky type to minimize turn-on losses and current over-shoot. Thermal Protection The LM5009 should be operated so the junction temperature does not exceed 125C during normal operation. An internal Thermal Shutdown circuit is provided to protect the LM5009 in the event of a higher than normal junction temperature. When activated, typically at 165C, the controller is forced into a low power reset state, disabling the buck switch. This feature prevents catastrophic failures from accidental device overheating. When the junction temperature reduces below 140C (typical hysteresis = 25C), the buck switch is enabled, and normal operation is resumed. 10 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 APPLICATIONS INFORMATION SELECTION OF EXTERNAL COMPONENTS A guide for determining the component values will be illustrated with a design example. Refer to Figure 8. The following steps will configure the LM5009 for: * Input voltage range (Vin): 12V to 90V * Output voltage (VOUT1): 10V * Load current (for continuous conduction mode): 100mA to 150mA R1 and R2: From Figure 8, VOUT1 = VFB x (R1 + R2) / R2, and since VFB = 2.5V, the ratio of R1 to R2 calculates as 3:1. Standard values of 3.01 k (R1) and 1.00 k (R2) are chosen. Other values could be used as long as the 3:1 ratio is maintained. The selected values, however, provide a small amount of output loading (2.5 mA) in the event the main load is disconnected. This allows the circuit to maintain regulation until the main load is reconnected. Fs and RON: Unless the application requires a specific frequency, the choice of frequency is generally a compromise since it affects the size of L1 and C2, and the switching losses. The maximum allowed frequency, based on a minimum on-time of 250 ns, is calculated from: FMAX = VOUT / (VINMAX x 250 ns) (6) For this exercise, Fmax = 444 kHz. From Equation 2, RON calculates to 180 k. A standard value 237 k resistor will be used to allow for tolerances in Equation 2, resulting in a nominal frequency of 337 kHz. L1: The main parameter affected by the inductor is the output current ripple amplitude. The choice of inductor value therefore depends on both the minimum and maximum load currents, keeping in mind that the maximum ripple current occurs at maximum Vin. a) Minimum load current: To maintain continuous conduction at minimum Io (100 mA), the ripple amplitude (IOR) must be less than 200 mA peak-to-peak so the lower peak of the waveform does not reach zero. L1 is calculated using the following equation: VOUT1 x (VIN - VOUT1) L1 = IOR x Fs x VIN (7) At Vin = 90V, L1(min) calculates to 132 H. The next larger standard value (150 H) is chosen and with this value IOR calculates to 176 mA peak-to-peak at Vin = 90V, and 33 mA peak-to-peak at Vin = 12V. b) Maximum load current: At a load current of 150 mA, the peak of the ripple waveform must not reach the minimum value of the LM5009's current limit threshold (250 mA). Therefore the ripple amplitude must be less than 200 mA peak-to-peak, which is already satisfied in the above calculation. With L1 = 150 H, at maximum Vin and Io, the peak of the ripple will be 238 mA. While L1 must carry this peak current without saturating or exceeding its temperature rating, it also must be capable of carrying the maximum value of the LM5009's current limit threshold (370 mA) without saturating, since the current limit is reached during startup. C3: The capacitor on the VCC output 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. C2, and R3: When selecting the output filter capacitor C2, the items to consider are ripple voltage due to its ESR, ripple voltage due to its capacitance, and the nature of the load. a) ESR and R3: A low ESR for C2 is generally desirable so as to minimize power losses and heating within the capacitor. However, this regulator requires a minimum amount of ripple voltage at the feedback input for proper loop operation. For the LM5009 the minimum ripple required at pin 5 is 25 mV peak-to-peak, requiring a minimum ripple at VOUT1 of 100 mV. Since the minimum ripple current (at minimum Vin) is 33 mA peak-to-peak, the minimum ESR required at VOUT1 is 3 . Since quality capacitors for SMPS applications have an ESR considerably less than this, R3 is inserted as shown in Figure 8. R3's value, along with C2's ESR, must result in at least 25 mV peak-to-peak ripple at pin 5. Generally, R3 will be 0.5 to 5.0 . b) Nature of the Load: The load can be connected to VOUT1 or VOUT2. VOUT1 provides good regulation, but with a ripple voltage which ranges from 100 mV (at Vin = 12V) to 580 mV (at Vin = 90V). Alternatively, VOUT2 provides low ripple (3 mV to 13 mV) but lower regulation due to R3. Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 11 LM5009 SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 www.ti.com C2 should generally be no smaller than 3.3 F. Typically, its value is 10 F to 20 F, with the optimum value determined by the load. If the load current is fairly constant, a small value suffices for C2. If the load current includes significant transients, a larger value is necessary. For each application, experimentation is needed to determine the optimum values for R3 and C2. C) Ripple Reduction: The ripple amplitude at VOUT1 can be reduced by reducing R3, and adding a capacitor across R1 so as to transfer the ripple at VOUT1 directly to the FB pin, without attenuation. The new value of R3 is calculated from: R3 = 25 mV/IOR(min) (8) where IOR(min) is the minimum ripple current amplitude - 33 mAp-p in this example. The added capacitor's value is calculated from: C = TON(max)/(R1 // R2) (9) where TON(max) is the maximum on-time (at minimum Vin). The selected capacitor should be larger than the value calculated above. RCL: When a current limit condition is detected, the minimum off-time set by this resistor must be greater than the maximum normal off-time which occurs at maximum Vin. Using Equation 4, the minimum on-time is 0.329 s, yielding a maximum off-time of 2.63 s. This is increased by 82 ns (to 2.72 s) due to a 25% tolerance of the on-time. This value is then increased to allow for: The response time of the current limit detection loop (400ns). The off-time determined by Equation 5 has a 25% tolerance: tOFFCL(MIN) = (2.72 s x 1.25) + 0.4 s= 3.8 s (10) Using Equation 5, RCL calculates to 167 k (at VFB = 2.5V). The closest standard value is 169 k. D1: The important parameters are reverse recovery time and forward voltage. The reverse recovery time determines how long the reverse 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 only this diode's voltage which forces the inductor current to reduce during the forced off-time. For this reason, a higher voltage is better, although that affects efficiency. A good choice is an ultrafast power or Schottky diode with a reverse recovery time of 30 ns, and a forward voltage drop of 0.7V. Other types of diodes may have a lower forward voltage drop, but may have longer recovery times, or greater reverse leakage. D1's reverse voltage rating must be at least as great as the maximum Vin, and its current rating be greater than the maximum current limit threshold (370 mA). C1: This capacitor's purpose is to supply most of the switch current during the on-time, and limit the voltage ripple at VIN, on the assumption that the voltage source feeding VIN has an output impedance greater than zero. At maximum load current, when the buck switch turns on, the current into pin 8 will suddenly increase to the lower peak of the output current waveform, ramp up to the peak value, then drop to zero at turn-off. The average input current during this on-time is the load current (150 mA). For a worst case calculation, C1 must supply this average load current during the maximum on-time. To keep the input voltage ripple to less than 2V (for this exercise), C1 calculates to: C1 = I x tON 'V = 0.15A x 2.47 Ps 2.0V = 0.185 PF (11) Quality ceramic capacitors in this value have a low ESR which adds only a few millivolts to the ripple. It is the capacitance which is dominant in this case. To allow for the capacitor's tolerance, temperature effects, and voltage effects, a 1.0 F, 100V, X7R capacitor will be used. C4: The recommended value is 0.022 F for C4, as this is appropriate in the majority of applications. 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 quick recharge during each off-time. At minimum VIN, when the on-time is at maximum, it is possible during start-up that C4 will not fully recharge during each 300 ns offtime. The circuit will not be able to complete the start-up, and achieve output regulation. This can occur when the frequency is intended to be low (e.g., RON = 500K). In this case C4 should be increased so it can maintain sufficient voltage across the buck switch driver during each on-time. C5: This capacitor helps avoid supply voltage transients and ringing due to long lead inductance at VIN. A low ESR, 0.1F ceramic chip capacitor is recommended, located close to the LM5009. 12 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 FINAL CIRCUIT The final circuit is shown in Figure 12. The circuit was tested, and the resulting performance is shown in Figure 13 through Figure 16. For these graphs, the load current was varied from 50mA to 200mA. MINIMUM LOAD CURRENT A minimum load current of 1 mA is required to maintain proper operation. If the load current falls below that level, the bootstrap capacitor may discharge during the long off-time, and the circuit will either shutdown, or cycle on and off at a low frequency. If the load current is expected to drop below 1 mA in the application, the feedback resistors should be chosen low enough in value so they provide the minimum required current at nominal Vout. PC BOARD LAYOUT The LM5009 regulation and over-voltage comparators are very fast, and as such will respond to short duration noise pulses. Layout considerations are therefore critical for optimum performance. The components at pins 1, 2, 3, 5, and 6 should be as physically close as possible to the IC, thereby minimizing noise pickup in the PC tracks. The current loop formed by D1, L1, and C2 should be as small as possible. The ground connection from C2 to C1 should be as short and direct as possible. If the internal dissipation of the LM5009 produces excessive 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 bottom of the WSON-8 package can be soldered to a ground plane on the PC board, and that plane should extend out from beneath the IC to help dissipate the heat. Additionally, the use of wide PC board traces, where possible, can also help conduct heat away from the IC. Judicious positioning of the PC board within the end product, along with use of any available air flow (forced or natural convection) can help reduce the junction temperatures. 12V - 90V Input VCC VIN 7 8 C1 1.0 PF C3 0.1 PF C5 0.1 PF BST RON 237k 2 RON/SD C4 0.022 PF LM5009 6 L1 150 PH 10.0V SW VOUT1 1 SHUTDOWN D1 RCL R1 3.01k 3 VOUT2 RCL 169k R3 3.0 FB RTN 5 4 R2 1.0k C2 15 PF GND Figure 12. LM5009 Example Circuit Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 13 LM5009 SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 www.ti.com Table 2. Bill of Materials (Circuit of Figure 12) Item Description Part Number Value C1 Ceramic Capacitor TDK C4532X7R2A105M 1 F, 100V C2 Ceramic Capacitor TDK C4532X7R1E156M 15 F, 25V C3 Ceramic Capacitor Kemet C1206C104K5RAC 0.1 F, 50V C4 Ceramic Capacitor Kemet C1206C223K5RAC 0.022 F, 50V C5 Ceramic Capacitor TDK C3216X7R2A104M 0.1 F, 100V D1 Schottky Power Diode Diodes Inc. DFLS1100 100V, 1A L1 Power Inductor TDK SLF7045T-151MR33 150 H R1 Resistor Vishay CRCW12063011F 3.01 k R2 Resistor Vishay CRCW12061001F 1.0 k R3 Resistor Vishay CRCW12063R00F 3.0 RON Resistor Vishay CRCW12062373F 237 k RCL Resistor Vishay CRCW12061693F 169 k U1 Switching Regulator LM5009 100 100 Vin = 12V EFFICIENCY (%) EFFICIENCY (%) 80 Vin = 48V 70 IOUT = 200 mA 90 90 Vin = 30V Vin = 90V 80 IOUT = 100 mA 70 60 60 50 50 50 100 150 200 0 20 LOAD CURRENT (mA) 80 100 Figure 14. Efficiency vs VIN and Load Current 330 LOAD CURRENT @ CURRENT LIMIT ONSET (mA) 10.4 10.2 VOUT (V) 60 VIN (V) Figure 13. Efficiency vs Load Current and VIN 10.0 9.8 9.6 Vin = 48V 9.4 310 290 270 250 230 50 100 150 200 LOAD CURRENT (mA) 0 20 40 60 80 100 VIN (V) Figure 15. VOUT vs Load Current 14 40 Submit Documentation Feedback Figure 16. Current Limit vs VIN Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 LM5009 www.ti.com SNVS402G - FEBRUARY 2006 - REVISED FEBRUARY 2013 REVISION HISTORY Changes from Revision F (February 2013) to Revision G * Page Changed layout of National Data Sheet to TI format .......................................................................................................... 14 Submit Documentation Feedback Copyright (c) 2006-2013, Texas Instruments Incorporated Product Folder Links: LM5009 15 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) LM5009MM NRND VSSOP DGK 8 1000 TBD Call TI Call TI -40 to 125 SLLB LM5009MM/NOPB ACTIVE VSSOP DGK 8 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SLLB LM5009MMX NRND VSSOP DGK 8 3500 TBD Call TI Call TI -40 to 125 SLLB LM5009MMX/NOPB ACTIVE VSSOP DGK 8 3500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SLLB LM5009SDC/NOPB ACTIVE WSON NGU 8 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 5009SD LM5009SDCX/NOPB ACTIVE WSON NGU 8 4500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 5009SD (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. 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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) W Pin1 (mm) Quadrant LM5009SDC/NOPB WSON NGU 8 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 LM5009SDCX/NOPB WSON NGU 8 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 Pack Materials-Page 1 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) LM5009SDC/NOPB WSON NGU 8 1000 210.0 185.0 35.0 LM5009SDCX/NOPB WSON NGU 8 4500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA NGU0008B SDC08B (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. 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