LM5009 150 mA, 100V Step-Down Switching Regulator General Description Features 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 MSOP-8 and the thermally enhanced LLP-8 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 hysteretic 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 hysteretic control 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. n n n n n n n n n n n n n Integrated N-Channel MOSFET Guaranteed 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 -40˚C to 125˚C Internal startup regulator Intelligent current limit protection External shutdown control Thermal shutdown MSOP-8 and thermally enhanced LLP packages Typical Applications n Heat sink eliminator for classic linear regulator applications n 12V, 24V, 36V, and 48V rectified AC systems n 42V Automotive n Non-isolated AC mains charge coupled supplies n LED Current Source Package n MSOP - 8 n LLP - 8 (4mm x 4mm) (Available Soon) Typical Application Circuit 20165828 Basic Stepdown Regulator © 2006 National Semiconductor Corporation DS201658 www.national.com LM5009 150 mA, 100V Step-Down Switching Regulator February 2006 LM5009 Connection Diagram 20165802 8-Lead MSOP, LLP Ordering Information Order Number Package Type NSC Package Drawing Supplied As LM5009MM MSOP-8 MUA08A 1000 Units on Tape and Reel LM5009MMX MSOP-8 MUA08A 3500 Units per Reel LM5009SD LLP-8 Available Soon LM5009SDX LLP-8 Available Soon www.national.com 2 LM5009 Pin Descriptions Pin Name 1 SW Switching output Description Power switching output. Connect to the inductor, re-circulating diode, and bootstrap capacitor. Application Information 2 BST Boost Pin An external capacitor is required between the BST and the SW pins. A 0.01µF 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 35µs 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 setpoint (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 0.1µF decoupling capacitor is required. 8 VIN Input voltage Recommended operating range: 9.5V to 95V. EP Exposed Pad (LLP 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. 3 www.national.com LM5009 Absolute Maximum Ratings (Note 1) BST to SW If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VCC to RTN 14V All Other Inputs to RTN -0.3 to 7V Storage Temperature Range -65˚C to +150˚C VIN to RTN 14V -0.3V to 100V BST to RTN -0.3V to 114V SW to RTN (Steady State) -1V Operating Ratings (Note 1) VIN ESD Rating (Note 5) Human Body Model 2kV BST to VCC 9.5V to 95V Operating Junction Temperature −40˚C to + 125˚C 100V Electrical Characteristics Limits in standard type are for TJ = 25˚C only, and limits in boldface type apply over the junction temperature (TJ) range of -40˚C to +125˚C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25˚C, and are provided for reference purposes only. Unless otherwise stated, the following conditions apply: VIN = 48V, RON = 200kΩ. See (Note 3) Symbol Parameter Conditions Min Typ Max 7 7.4 Units VCC Supply VCC Reg VCC Regulator Output VCC Current Limit 6.6 (Note 4) VCC undervoltage Lockout Voltage (VCC increasing) VCC Undervoltage Hysteresis V 9.5 mA 6.3 V 200 mV VCC UVLO Delay (filter) 100mV overdrive 10 IIN Operating Current Non-Switching, FB = 3V 485 675 µA IIN Shutdown Current RON/SD = 0V 76 150 µA Buck Switch Rds(on) ITEST = 200mA, (Note 6) 2.0 4.4 Ω Gate Drive UVLO VBST − VSW Rising 4.5 5.5 µs Switch Characteristics 3.4 Gate Drive UVLO Hysteresis 430 V mV Current Limit Current Limit Threshold Current Limit Response Time 0.25 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 µs 2.56 µs On Time Generator TON - 1 Vin = 10V Ron = 200K 2.15 2.77 3.5 µs TON - 2 Vin = 95V Ron = 200K 200 300 420 ns Remote Shutdown Threshold Rising 0.40 0.70 1.05 V Remote Shutdown Hysteresis www.national.com 35 4 mV (Continued) Limits in standard type are for TJ = 25˚C only, and limits in boldface type apply over the junction temperature (TJ) range of -40˚C to +125˚C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25˚C, and are provided for reference purposes only. Unless otherwise stated, the following conditions apply: VIN = 48V, RON = 200kΩ. See (Note 3) Symbol Parameter Conditions Min Typ Max Units Minimum Off Time Minimum Off Timer FB = 0V 300 ns 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 Temp. 165 ˚C Thermal Shutdown Hysteresis 25 ˚C 200 ˚C/W FB Bias Current Thermal Shutdown Tsd Thermal Resistance θJA Junction to Ambient MUA Package SDC Package ˚C/W Note 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 guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: For detailed information on soldering plastic MSOP and LLP packages, refer to the Packaging Data Book available from National Semiconductor Corporation. Note 3: All limits are guaranteed. All electrical characteristics having room temperature limits are tested during production with TA = TJ = 25˚C. All hot and cold limits are guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control. Note 4: The VCC output is intended as a self bias for the internal gate drive power and control circuits. Device thermal limitations limit external loading. Note 5: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. All pins are rated for 2 kV, except VIN and VCC which are rated for 1 kV. Note 6: For devices procured in the LLP-8 package the Rds(on) limits are guaranteed by design characterization data only. 5 www.national.com LM5009 Electrical Characteristics LM5009 Typical Performance Characteristics On-Time vs VIN and RON VCC vs VIN and FS 20165829 20165809 Current Limit Off-Time vs VFB and RCL VCC vs ICC and VIN 20165812 20165830 ICC Current vs Applied VCC Voltage 20165811 www.national.com 6 LM5009 Typical Application Circuit and Block Diagram 20165801 FIGURE 1. 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: 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 MSOP-8 and the thermally enhanced LLP-8 packages. The regulator is based on a hysteretic control scheme using an on-time inversely proportional to VIN. The hysteretic control 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 1. 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 undervoltage lockout, Max Duty Cycle limit timer and the intelligent current limit off timer. Hysteretic Control Circuit Overview 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: 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 7 www.national.com LM5009 Hysteretic Control Circuit Overview (Continued) (1) The output voltage (VOUT) is programmed by two external resistors as shown in Figure 1. The regulation point is calculated as follows: VOUT = 2.5 x (R1 + R2) / R2 All hysteretic regulators regulate 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 1). 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 2. However, R3 slightly degrades the load regulation. 20165806 FIGURE 3. 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. Over-Voltage Comparator 20165805 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. FIGURE 2. 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 3. The current required into the VCC pin is shown in the Typical Performance Characteristics. www.national.com 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: (2) TON = 1.25 x 10-10 x RON / VIN 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 4. The voltage at the RON/SD pin is between 1.7V and 5V, depending on Vin and the value of the RON resistor. 8 LM5009 ON-Time Generator and Shutdown (Continued) 20165807 FIGURE 4. Shutdown Implementation When activated, typically at 165˚C, 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 140˚C (typical hysteresis = 25˚C), the buck switch is enabled, and normal operation is resumed. 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 35µs. 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 35µs. 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: TOFF = 10-5 / (0.285 + (VFB / 6.35 x 10-6 x RCL)) (3) The current limit sensing circuit is blanked for the first 5070ns 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 turn-off recovery. Applications Information SELECTION OF EXTERNAL COMPONENTS A guide for determining the component values will be illustrated with a design example. Refer to Figure 1. 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 1, 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 kΩ (R1) and 1.00 kΩ (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) For this exercise, Fmax = 444 kHz. From equation 1, RON calculates to 180 kΩ. A standard value 237 kΩ resistor will be used to allow for tolerances in equation 1, 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 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 0.01µF 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. 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 125˚C during normal operation. An internal Thermal Shutdown circuit is provided to protect the LM5009 in the event of a higher than normal junction temperature. 9 www.national.com LM5009 Applications Information (Continued) where IOR(min) is the minimum ripple current amplitude - 33 mAp-p in this example. The added capacitor’s value is calculated from: be less than 200 mA p-p so the lower peak of the waveform does not reach zero. L1 is calculated using the following equation: C = TON(max)/(R1 // R2) 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 2, the minimum on-time is 0.329 µs, yielding a maximum off-time of 2.63 µs. This is increased by 82 ns (to 2.72 µs) due to a ± 25% tolerance of the on-time. This value is then increased to allow for: At Vin = 90V, L1(min) calculates to 132 µH. The next larger standard value (150 µH) is chosen and with this value IOR calculates to 176 mA p-p at Vin = 90V, and 33 mA p-p 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 guaranteed value of the LM5009’s current limit threshold (250 mA). Therefore the ripple amplitude must be less than 200 mA p-p, which is already satisfied in the above calculation. With L1 = 150 µH, 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 guaranteed 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 µF. 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, a hysteretic 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 p-p, requiring a minimum ripple at VOUT1 of 100 mV. Since the minimum ripple current (at minimum Vin) is 33 mA p-p, the minimum ESR required at VOUT1 is 3 Ω. Since quality capacitors for SMPS applications have an ESR considerably less than this, R3 is inserted as shown in Figure 1. R3’s value, along with C2’s ESR, must result in at least 25 mV p-p ripple at pin 5. Generally, R3 will be 0.5 Ω to 5.0 Ω. 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 ( @ Vin = 12V) to 580 mV (@Vin = 90V). Alternatively, VOUT2 provides low ripple (3 mV to 13 mV) but lower regulation due to R3. C2 should generally be no smaller than 3.3 µF. Typically, its value is 10 µF to 20 µF, 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 tranfer the ripple at VOUT1 directly to the FB pin, without attenuation. The new value of R3 is calculated from: The response time of the current limit detection loop (400ns), The off-time determined by equation 3 has a ± 25% tolerance, tOFFCL(MIN) = (2.72 µs x 1.25) + 0.4 µs= 3.8 µs Using equation 3, RCL calculates to 167 kΩ (at VFB = 2.5V). The closest standard value is 169 kΩ. 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 ontime. To keep the input voltage ripple to less than 2V (for this exercise), C1 calculates to: 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 µF, 100V, X7R capacitor will be used. C4: The recommended value is 0.01µF for C4, as this is appropriate in the majority of applications. A high quality ceramic capacitor, with low ESR is recommended as C4 R3 = 25 mV/IOR(min) www.national.com 10 mum 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. (Continued) 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 off-time. 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. 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 LLP-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. C5: This capacitor helps avoid supply voltage transients and ringing due to long lead inductance at VIN. A low ESR, 0.1µF ceramic chip capacitor is recommended, located close to the LM5009. FINAL CIRCUIT The final circuit is shown in Figure 5. The circuit was tested, and the resulting performance is shown in Figure 6 through Figure 9. For these graphs, the load current was varied from 50mA to 200mA. 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 opti- 20165822 FIGURE 5. LM5009 Example Circuit 11 www.national.com LM5009 Applications Information LM5009 Applications Information (Continued) Bill of Materials (Circuit of Figure 5) Item Description Part Number Value C1 Ceramic Capacitor TDK C4532X7R2A105M 1µF, 100V C2 Ceramic Capacitor TDK C4532X7R1E156M 15µF, 25V C3 Ceramic Capacitor Kemet C1206C104K5RAC 0.1µF, 50V C4 Ceramic Capacitor Kemet C1206C103K5RAC 0.01µF, 50V C5 Ceramic Capacitor TDK C3216X7R2A104M 0.1µF, 100V D1 UltraFast Power Diode Diodes Inc. DFLS1100 100V, 1A L1 Power Inductor TDK SLF7045T-151MR33 150 µH R1 Resistor Vishay CRCW12063011F 3.01 kΩ R2 Resistor Vishay CRCW12061001F 1.0 kΩ R3 Resistor Vishay CRCW12063R00F 3.0 Ω RON Resistor Vishay CRCW12062373F 237 kΩ RCL Resistor Vishay CRCW12061693F 169 kΩ U1 Switching Regulator National Semiconductor LM5009 20165823 FIGURE 6. Efficiency vs Load Current and VIN 20165827 FIGURE 7. Efficiency vs VIN and Load Current www.national.com 12 LM5009 Applications Information (Continued) 20165824 FIGURE 8. VOUT vs Load Current 20165831 FIGURE 9. Current Limit vs VIN 13 www.national.com LM5009 150 mA, 100V Step-Down Switching Regulator Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead MSOP Package NS Package Number MUA08A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. 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