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SC4518HEVB - 600kHz, 2A Step-Down Switching Regulator - Semtech Corporation

型  号:
SC4518HEVB
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266.63KB 共15页
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SEMTECH[SemtechCorporation]
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SC4518HEVB - 600kHz, 2A Step-Down Switching Regulator - Semtech Corporation
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600kHz, 2A Step-Down Switching Regulator POWER MANAGEMENT Description The SC4518H is a current mode switching regulator with an integrated switch, operating at 600kHz with separate sync and enable functions. The integrated switch allows for cost effective low power solutions (peak switch current 2 amps). The sync function allows customers to synchronize to a faster clock in order to avoid frequency beating in noise sensitive applications. High frequency of operation allows for very small passive components. Current mode operation allows for fast dynamic response and instantaneous duty cycle adjustment as the input varies (ideal for CPE applications where the input is a wall plug power). The low shutdown current makes it ideal for portable applications where battery life is important. The SC4518H is a 600kHz switching regulator synchronizable to a faster frequency from 750kHz to 1.2MHz. SC4518H Features Wide operating voltage range: 4.4V to 24V Integrated 2 Amp switch 600kHz frequency of operation Current mode controller Synchronizable to higher frequency up to 1.2MHz Precision enable threshold SO-8 EDP package. Lead free product, fully WEEE and RoHS compliant Applications XDSL modems CPE equipment DC-DC point of load applications Portable equipment Typical Application Circuit D1 1 VIN Enable C3 2 5 8 BST IN SW 3 6 7 C1 L1 VOUT R1 SC4518H EN SYNC FB COMP GND 4 D2 R2 C2 C4 R3 Revision: August 22, 2007 1 www.semtech.com SC4518H POWER MANAGEMENT Absolute Maximum Ratings Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability. Parameter Input Supply Voltage Boost Pin Above VSW Boost Pin Voltage EN Pin Voltage FB Pin Voltage FB Pin Current SYNC Pin Current Thermal Impedance Junction to Ambient Operating Ambient Temperature Range Maximum Junction Temperature Storage Temperature Range Lead Temperature (Soldering) 10 sec ESD Rating (Human Body Model) Symbol VIN (VBST - VSW) V BST V EN V FB IFB ISYNC θJ A TA TJ TSTG TLEAD ESD Limits -0.3 to +28 16 -0.3 to +32 -0.3 to +24 -0.3 to +6 1 1 36.5(2) -40 to +85 +150 -65 to +150 300 2 (1) Units V V V V V mA mA °C/W °C °C °C °C kV Notes: (1) For proper operation of device, VIN should be within maximum Operating Input Voltage as defined in Electrical Characteristics. (2) Minimum pad size. Electrical Characteristics Unless specified: VIN = 12V, VCOMP = 0.8V, VBST = VIN + 5V, EN = tied to VIN, SYNC = 0, SW = open. TA = TJ = -40°C to 125°C. Parameter Operating Input Voltage Maximum Switch Current Limit Oscillator Frequency Switch On Voltage Drop VIN Undervoltage Lockout VIN UVLO Hysteresis VIN Supply Current Standby Current Symbol VIN ISW fOSC VD(SW) VUVLO Conditions Min Typ Max 24 (1) Units V A kHz mV TA = 25°C, D = 50% 2.0 500 600 330 3.9 60 3.0 700 ISW = 2A 4.4 V mV IQ IQ(OFF) V FB = 1V V E N = 0V 3 100 5 150 mA µA  2007 Semtech Corp. 2 www.semtech.com SC4518H POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: VIN = 12V, VCOMP = 0.8V, VBST = VIN + 5V, EN = tied to VIN, SYNC = 0, SW = open. TA = TJ = -40°C to 125°C. PARAMETER FB Input Current Feedback Voltage Feedback Voltage Line Regulation FB to VCOMP Voltage Gain(3) FB to VCOMP Transconductance(3) VCOMP Pin Source Current VCOMP Pin Sink Current VCOMP Pin to Switch Current Transconductance VCOMP Pin Maximum Switching Threshold VCOMP OCP Threshold VCOMP Hiccup Retry Threshold Maximum Switch Duty Cycle Minimum Boost Voltage Above Switch (3) Boost Current SYMBOL IFB CONDITIONS MIN TYP -0.25 MAX -1 0.816 UNITS µA V mV/V V/V 0.784 4.4V < VIN < 24V(2) 0.9V ≤ VCOMP ≤ 2.0V ∆ ICOMP = ± 10µA VFB = 0.6V VFB = 1.0V VCOMP = 1.25V Duty cycle = 0% VCOMP rising VCOMP falling VCOMP = 1.2V, ISW = 400mA 85 150 500 0.8 +3 350 850 70 -70 3 0.6 2 0.25 1300 110 -110 µMho µA µA A/V V V V % 2.7 ISW = 0.5A ISW = 2A 10 30 15 45 V mA  2007 Semtech Corp. 3 www.semtech.com SC4518H POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: VIN = 12V, VCOMP = 0.8V, VBST = VIN + 5V, EN = tied to VIN, SYNC = 0, SW = open. TA = TJ = -40°C to 125°C. PARAMETER Enable Input Threshold Voltage Enable Output Bias Current SYMBOL VETH IEOL IEOH CONDITIONS MIN 1.1 TYP 1.3 8 10 1.5 MAX 1.5 UNITS V µA µA V EN = 50mV below threshold EN = 50mV above threshold SYNC Threshold Voltage SYNC Input Frequency SYNC Pin Resistance (4) 800 VSYNC = 0.5V 20 1200 kHz kΩ Notes: (1) The device may not function properly outside its operating input voltage. (2) The required input voltage for a regulated output depends on the output voltage and load condition. (3) Guaranteed by design. (4) Please contact factory for SYNC applications.  2007 Semtech Corp. 4 www.semtech.com SC4518H POWER MANAGEMENT Pin Configurations Ordering Information Part Number (2) SC4518HSETRT Package (1) SO-8 EDP EVALUATION BOARD TOP VIEW BST IN SW GND 1 2 3 4 8 7 6 5 SYNC COMP FB EN SC4518HEVB Notes: (1) Only available in tape and reel packaging. A reel contains 2500 devices. (2) Lead free product. This product is fully WEEE and RoHS compliant. (SO-8 EDP) Pin Descriptions Pin # 1 2 Pin Name Pin Function BST IN This pin provides power to the internal NPN switch. The minimum turn on voltage for this switch is 2.7V. Pin IN delivers all power required by control and power circuitry. This pin sees high di/dt during switching actions of the switch. A decoupling capacitor should be attached to this pin as close as possible. Pin SW is the emitter of the internal switch. The external freewheeling diode should be connected as close as possible to this pin. All voltages are measured with respect to this pin. The decoupling capacitor and the freewheeling diode should be connected to GND as short as possible. This is the chip enable input. The regulator is switched on if EN is high, and it is off if EN is low. The regulator is in standby mode when EN is low, and the input supply current is reduced to a few microamperes. Feedback input for adjustable output controllers. Thi s i s the output of the i nternal error ampli fi er and i nput of the peak current comparator. A compensation network is connected to this pin to achieve the specified performance. This is synchronous control pin used to synchronize the internal oscillator to an external pulse control signal. When not used, it should be connected to GND. 3 4 5 SW GND EN 6 7 8 - FB COMP SYNC THERMAL P ad for heatsi nki ng purposes. C onnect to ground plane usi ng multi ple vi as. Not connected PAD internally.  2007 Semtech Corp. 5 www.semtech.com SC4518H POWER MANAGEMENT Block Diagram + + SLOPE Is + ISEN IN 40m COMP FB BST - + EA PWM S R Q POWER TRANSISTOR SW Is 1V EN REFERENCE UVLO SOFT START HICCUP 0.7V SLOPE SLOPE COMP FB OL GND SYNC OSCILLATOR FREQUENCY CLK Typical Characteristic - OCP Limit SC4518H OCP Limit vs Duty Cycle 4.5 4 3.5 Current Limit (A) 3 2.5 2 1.5 1 0.5 0 20 40 60 80 100 Duty Cycle (%) ILIM @ -40C ILIM @ 25C ILIM @ 125C  2007 Semtech Corp. 6 www.semtech.com SC4518H POWER MANAGEMENT Application Information General Overview The SC4518H is a high frequency current mode buck PWM regulator. It has an internal clock with fixedfrequency. The SC4518H uses two feedback loops (voltage loop and current loop) that control the duty cycle of the internal power switch. The error amplifier functions like that of the voltage mode controller. The output of the error amplifier provides a switch current reference. This technique effectively removes one of the double poles in the output LC filter stage. With this, it is easier to compensate a current mode converter for better performance. A minimum 2.7V voltage is required to saturate the NPN power switch when it is ON to reduce its conduction loss. Current Limit and Over Current Protection The current sense amplifier in the SC4518H monitors the switch current during each cycle. Overcurrent protection (OCP) is triggered when the current limit exceeds the upper limit of 2A, detected by a voltage on COMP being greater than about 2V. When an OCP fault is detected, the switch is turned off and the external COMP capacitor is discharged at the rate of dv/dt = 3µA/ Ccomp. Once the COMP voltage has fallen below 250mV, the part enters a normal startup cycle. Ccomp is the total capacitance value attached to COMP. In the case of sustained overcurrent or dead-short, the part will continually cycle through the retry sequence as described above, at a rate dependent on the value of Ccomp. During start up, the voltage on COMP rises roughly at the rate of dv/dt = 120µA/Ccomp. Therefore, the retry time for a sustained overcurrent can be approximately calculated as: Tretry 2V 2V = Ccomp • + Ccomp • 120uA 3uA Enable Pulling and holding the EN pin below 0.4V activates the shut down mode of the SC4518H which reduces the input supply current to less than 150µA. During the shut down mode, the switch is turned off. The SC4518H is turned on if the EN pin is pulled high. Oscillator Its internal free running oscillator sets the PWM frequency at 600kHz for the SC4518H without any external components to program the frequency. An external clock with a duty cycle from 20% to 80% connected to the SYNC pin activates synchronous mode. The frequency of the external clock can be from 750kHz to 1.2MHz. UVLO When the EN pin is pulled and held above 1.8V, the voltage on Pin IN determines the operation of the SC4518H. As VIN increases during power up, the internal circuit senses VIN and keeps the power transistor off until VIN reaches 4.4V. Load Current The peak current IPEAK in the switch is internally limited. For a specific application, the allowed load current IOMAX will change if the input voltage drifts away from the original design as given for continuous current mode: IOMAX = 2 − VO ⋅ (1 − D) 2 ⋅ L ⋅ fs Figure 1 shows the voltage on COMP during a sustained overcurrent condition. Where: fs = switching frequency, Vo = output voltage and D = duty ratio, VO/VI V = input voltage. I Figure 1. Voltage on COMP for Startup and OCP Figure 2 shows the theoretical maximum load current for the specific cases. In a real application, however, the allowed maximum load current also depends on the layout and the air cooling condition. Therefore, the maximum load current may need to be derated according to the thermal situation of the application. 7 www.semtech.com  2007 Semtech Corp. SC4518H POWER MANAGEMENT Application Information (Cont.) Ip −p = ∆I • IOMAX Maximum Load Current vs Input Voltage L=10uH 1.900 1.880 1.860 1.840 1.820 1.800 1.780 1.760 1.740 1.720 1.700 4 6 8 10 12 14 16 18 Vi (V) IPEAK = IOMAX + Ip −p 2 Vo=2.5V Vo=3.3V Vo=5V After the required inductor value is selected, the proper selection of the core material is based on the peak inductor current and efficiency specifications. The core must be able to handle the peak inductor current IPEAK without saturation and produce low core loss during the high frequency operation. The power loss for the inductor includes its core loss and copper loss. If possible, the winding resistance should be minimized to reduce inductor’s copper loss. The core must be able to handle the peak inductor current I PEAK without saturation and produce low core loss during the high frequency operation. The power loss for the inductor includes its core loss and copper loss. If possible, the winding resistance should be minimized to reduce inductor’s copper loss. The core loss can be found in the manufacturer’s datasheet. The inductor’s copper loss can be estimated as follows: PCOPPER = I2LRMS ⋅ R WINDING Figure 2. Theoretical maximum load current curves Inductor Selection The factors for selecting the inductor include its cost, efficiency, size and EMI. For a typical SC4518H application, the inductor selection is mainly based on its value, saturation current and DC resistance. Increasing the inductor value will decrease the ripple level of the output voltage while the output transient response will be degraded. Low value inductors offer small size and fast transient responses while they cause large ripple currents, poor efficiencies and more output capacitance to filter out the large ripple currents. The inductor should be able to handle the peak current without saturating and its copper resistance in the winding should be as low as possible to minimize its resistive power loss. A good trade-off among its size, loss and cost is to set the inductor ripple current to be within 15% to 30% of the maximum output current. The inductor value can be determined according to its operating point under its continuous mode and the switching frequency as follows: L= VO ⋅ ( VI − VO ) VI ⋅ fs ⋅ ∆I ⋅ IOMAX Iomax (A) Where: ILRMS is the RMS current in the inductor. This current can be calculated as follows: ILRMS = IOMAX ⋅ 1 + 1 ⋅ ∆I2 3 Output Capacitor Selection Basically there are two major factors to consider in selecting the type and quantity of the output capacitors. The first one is the required ESR (Equivalent Series Resistance) which should be low enough to reduce the output voltage deviation during load changes. The second one is the required capacitance, which should be high enough to hold up the output voltage. Before the SC4518H regulates the inductor current to a new value during a load transient, the output capacitor delivers all the additional current needed by the load. The ESR and ESL of the output capacitor, the loop parasitic inductance between the output capacitor and the load combined with inductor ripple current are all major contributors to the output voltage ripple. Surface mount ceramic capacitors are recommended. 8 www.semtech.com Where: fs = switching frequency, ∆I = ratio of the peak to peak inductor current to the output load current and VO = output voltage. The peak to peak inductor current is:  2007 Semtech Corp. SC4518H POWER MANAGEMENT Application Information (Cont.) Input Capacitor Selection The input capacitor selection is based on its ripple current level, required capacitance and voltage rating. This capacitor must be able to provide the ripple current by the switching actions. For the continuous conduction mode, the RMS value of the input capacitor current ICIN(RMS) can be calculated from: ICIN (RMS ) VO ⋅ ( VI − VO ) = IOMAX ⋅ V 2I The required minimum capacitance for the boost capacitor will be: Cboost = IB ⋅ TW VD Where: IB = the boost current and VD= discharge ripple voltage. With fs = 600kHz, VD = 0.5V and IB =0.045A, the required minimum capacitance for the boost capacitor is: Cboost = IB 1 0.045 1 ⋅ ⋅ Dmax = ⋅ ⋅ 0.85 = 128nF VD fs 0.5 600k This current gives the capacitor’s power loss through its RCIN(ESR) as follows: PCIN = I2 CIN(RMS ) • R CIN(ESR ) The input ripple voltage mainly depends on the input capacitor’s ESR and its capacitance for a given load, input voltage and output voltage. Assuming that the input current of the converter is constant, the required input capacitance for a given voltage ripple can be calculated by: CIN = IOMAX ⋅ D ⋅ (1 − D) fs ⋅ ( ∆VI − IOMAX ⋅ R CIN(ESR ) ) The internal driver of the switch requires a minimum 2.7V to fully turn on that switch to reduce its conduction loss. If the output voltage is less than 2.7V, the boost capacitor can be connected to either the input side or an independent supply with a decoupling capacitor. But the Pin BST should not see a voltage higher than its maximum rating. Freewheeling Diode Selection This diode conducts during the switch’s off-time. The diode should have enough current capability for full load and short circuit conditions without any thermal concerns. Its maximum repetitive reverse block voltage has to be higher than the input voltage of the SC4518H. A low forward conduction drop is also required to increase the overall efficiency. The freewheeling diode should be turned on and off fast with minimum reverse recovery because the SC4518H is designed for high frequency applications. SS13 Schottky rectifier is recommended for certain applications. The average current of the diode, ID_AVG can be calculated by: ID _ AVG = IO max ⋅ (1 − D) Where: ∆VI = the given input voltage ripple. Because the input capacitor is exposed to the large surge current, attention is needed for the input capacitor. If tantalum capacitors are used at the input side of the converter, one needs to ensure that the RMS and surge ratings are not exceeded. For generic tantalum capacitors, it is suggested to derate their voltage ratings at a ratio of about two to protect these input capacitors. Boost Capacitor and its Supply Source Selection The boost capacitor selection is based on its discharge ripple voltage, worst case conduction time and boost current. The worst case conduction time Tw c an be estimated as follows: TW = 1 ⋅ Dmax fs Thermal Considerations There are three major power dissipation sources for the SC4518H. The internal switch conduction loss, its switching loss due to the high frequency switching actions and the base drive boost circuit loss. These losses can be estimated as: Ptotal = Io ⋅ R on ⋅ D + 10 .8 ⋅ 10 −3 ⋅ Io ⋅ VI + 9 2 Where: fs = the switching frequency and Dmax = maximum duty ratio, 0.85 for the SC4518H. 10 ⋅ Io ⋅ D ⋅ ( Vboost ) 500 www.semtech.com  2007 Semtech Corp. SC4518H POWER MANAGEMENT Application Information (Cont.) Where: IO = load current; R = on-equivalent resistance of the switch; ON VBOOST = input voltage or output based on the boost circuit connection. The junction temperature of the SC4518H can be further decided by: 1 IN EN GND SYNC BST 2 The goal of the compensation design is to shape the loop to have a high DC gain, high bandwidth, enough phase margin, and high attenuation for high frequency noises. Figure 3 gives a typical compensation network which offers 2 poles and 1 zero to the power stage: SC4518H SW FB COMP 3 6 7 R1 C L1 Vout TJ = TA + θJA ⋅ Ptotal 5 8 θ JA is the thermal resistance from junction to ambient. Its value is a function of the IC package, the application layout and the air cooling system. The freewheeling diode also contributes a significant portion of the total converter loss. This loss should be minimized to increase the converter efficiency by using Schottky diodes with low forward drop (VF). Pdiode = VF ⋅ Io ⋅ (1 − D) 4 C4 C5 R3 D2 R2 Figure 3. Compensation network provides 2 poles and 1 zero. The compensation network gives the following characteristics: s ωZ R2 ⋅ gm ⋅ GCOMP (s) = ω1 ⋅ s R1 + R 2 s ⋅ (1 + ) ωP 2 1+ Loop Compensation Design The SC4518H has an internal error amplifier and requires a compensation network to connect between the COMP pin and GND pin as shown in Figure 3. The compensation network includes C4, C5 and R3. R1 and R2 are used to program the output voltage according to: VO = 0.8 • (1 + R1 ) R2 Where: ω1 = 1 C 4 + C5 1 R3 ⋅ C4 Assuming the power stage ESR (equivalent series resistance) zero is an order of magnitude higher than the closed loop bandwidth, which is typically one tenth of the switching frequency, the power stage control to output transfer function with the current loop closed (Ridley model) for the SC4518H will be as follows: G VD (s ) = 3 ⋅ RL s 1+ 1 RL ⋅ C ωZ = ωP 2 = C 4 + C5 R 3 ⋅ C 4 ⋅ C5 The loop gain will be given by: s 1+ ωZ RL R2 1 ⋅ ⋅ T(s) = GCOMP (s) ⋅ G VD (s) = 2.55 ⋅ 10 ⋅ C 4 R1 + R 2 s (1 + s ) ⋅ (1 + s ) ωP1 ωP 2 −3 Where: RL – Load and C – Output capacitor.  2007 Semtech Corp. 10 www.semtech.com SC4518H POWER MANAGEMENT Application Information (Cont.) Where: ωp1 = 1 RL ⋅ C Layout Guidelines: In order to achieve optimal electrical and thermal performance for high frequency converters, special attention must be paid to the PCB layouts. The goal of layout optimization is to identify the high di/dt loops and minimize them. The following guidelines should be used to ensure proper operation of the converters. 1. A ground plane is suggested to minimize switching noises and trace losses and maximize heat transferring. 2. Start the PCB layout by placing the power components first. Arrange the power circuit to achieve a clean power flow route. Put all power connections on one side of the PCB with wide copper filled areas if possible. 3. The VIN bypass capacitor should be placed next to the VIN and GND pins. 4. The trace connecting the feedback resistors to the output should be short, direct and far away from any noise sources such as switching node and switching components. 5. Minimize the loop including input capacitor, the SC4518H and freewheeling diode D 2. This loop passes high di/dt current. Make sure the trace width is wide enough to reduce copper losses in this loop. 6. Maximize the trace width of the loop connecting the inductor, freewheeling diode D 2 a nd the output capacitor. 7. Connect the ground of the feedback divider and the compensation components directly to the GND pin of the SC4518H by using a separate ground trace. 8. Connect Pin 4 to a large copper area to remove the IC heat and increase the power capability of the SC4518H. A few feedthrough holes are required to connect this large copper area to a ground plane to further improve the thermal environment of the SC4518H. The traces attached to other pins should be as wide as possible for the same purpose. One integrator is added at origin to increase the DC gain. ωZ is used to cancel the power stage pole ωP1 so that the loop gain has –20dB/dec rate when it reaches 0dB line. ωP2 is placed at half switching frequency to reject high frequency switching noises. Figure 4 gives the asymptotic diagrams of the power stage with current loop closed and its loop gain. Mag Loop gain T(s) ωp1 Power stage ωC ωZ ωP2 ω Figure 4. Asymptotic diagrams of power stage with current loop closed and its loop gain. The design guidelines for the SC4518H applications are as following: 1. Set the loop gain crossover corner frequency ω C for given switching corner frequency ωC = 2πf . c 2. Place an integrator at the origin to increase DC and low frequency gains. 3. Select ωZ such that it is placed at ωP1 to obtain a -20dB/dec rate to go across the 0dB line. 4. Place a high frequency compensator pole ωP2 (ωP2 = πfs) to get the maximum attenuation of the switching ripple and high frequency noise with the adequate phase lag at ωC.  2007 Semtech Corp. 11 www.semtech.com SC4518H POWER MANAGEMENT Application Information (Cont.) Design Example 1. 12V to 5V. VI =12V C3 10u C1 0.22u 1 BST 2 IN 4.75k R4 8 5 EN GND SYNC 4 FB COMP 3 6 7 D3 L1 10uH R1 52.3k Vo=5V C2 47u SW SC4518H SC4518 C5 180p C4 6.8n R3 8.06k R2 10k D2 Bill of Materials Item 1 2 3 4 5 6 7 8 9 10 11 12 13 Qty 1 1 1 1 1 1 1 1 1 1 1 1 1 C1 C2 C3 C4 C5 D3 D2 L1 R1 R2 R3 R4 U1 Reference Value 0.22uF, 25V, X7R, 0805 47uF, 6.3V, 1210 10uF, 25V, 1210 6.8nF, 25V, 0805 180pF, 50V, 0805 1N4148WS, SOD-323 S S 23 10uH 52.3k, 1%, 0805 10k, 1%. 0805 8.06k, 0805 4.75k, 0805 S C 4518H Fairchild P/N: SS23 Cooper P/N: DR74-100 SMTZONE SMTZONE SMTZONE SMTZONE Semtech P/N: SC4518HSTRT Part No./Manufacturer Vishay P/N: VJ0805Y224KXX Murata Panasonic Vishay Vishay Unless specified, all resistors have 1% precision with 0603 package. Resistors are +/-1% and all capacitors are +/-20%  2007 Semtech Corp. 12 www.semtech.com SC4518H POWER MANAGEMENT Application Information (Cont.) (COMPONENT - TOP) (COMPONENT - BOTTOM) SC4518H 8 (PCB - TOP) (PCB - BOTTOM)  2007 Semtech Corp. 13 www.semtech.com SC4518H POWER MANAGEMENT Outline Drawing - SOIC-8L EDP A N 2X E/2 E1 E 1 ccc C 2X N/2 TIPS 2 e/2 B D aaa C SEATING PLANE A2 A C bxN bbb F EXPOSED PAD H H GAGE PLANE 0.25 L (L1) h A1 C A-B D e D DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX A A1 A2 b c D E1 E e F H h L L1 N 01 aaa bbb ccc .069 .053 .005 .000 .065 .049 .012 .020 .010 .007 .189 .193 .197 .150 .154 .157 .236 BSC .050 BSC .116 .120 .130 .085 .095 .099 .010 .020 .016 .028 .041 (.041) 8 0° 8° .004 .010 .008 1.75 1.35 0.13 0.00 1.65 1.25 0.31 0.51 0.25 0.17 4.80 4.90 5.00 3.80 3.90 4.00 6.00 BSC 1.27 BSC 2.95 3.05 3.30 2.15 2.41 2.51 0.25 0.50 0.40 0.72 1.04 (1.05) 8 8° 0° 0.10 0.25 0.20 h c 01 SEE DETAIL SIDE VIEW NOTES: 1. A DETAIL A CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE -H3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 4. REFERENCE JEDEC STD MS-012, VARIATION BA.  2007 Semtech Corp. 14 www.semtech.com SC4518H POWER MANAGEMENT Land Pattern - SOIC-8L EDP E D SOLDER MASK DIM (C) F G Z C D E F G P X Y Z DIMENSIONS INCHES MILLIMETERS (.205) .134 .201 .101 .118 .050 .024 .087 .291 (5.20) 3.40 5.10 2.56 3.00 1.27 0.60 2.20 7.40 Y THERMAL VIA Ø 0.36mm NOTES: 1. P X THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 2. REFERENCE IPC-SM-782A, RLP NO. 300A. 3. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804  2007 Semtech Corp. 15 www.semtech.com

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