MP44011HS-LF-Z

MP2355 3A, 23V, 380KHz Step-Down Converter The Future of Analog IC Technology DESCRIPTION FEATURES The MP2355 is a step-down regulator with a built in internal Power MOSFET. It achieves 3A continuous output current over a wide input supply range with excellent load and line regulation. • • • Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. Adjustable soft-start reduces the stress on the input source at turn-on. In shutdown mode the regulator draws 20μA of supply current. The MP2355 uses a minimum number of readily available external components to complete a 3A step-down DC to DC converter solution. EVALUATION BOARD REFERENCE • • • • • • • • Programmable Soft-Start 100mΩ Internal Power MOSFET Switch Stable with Low ESR Output Ceramic Capacitors Up to 95% Efficiency 20μA Shutdown Mode 3A Output Current Wide 4.75V to 23V Operating Input Range Fixed 380KHz Frequency Thermal Shutdown Cycle-by-Cycle Over Current Protection Under Voltage Lockout APPLICATIONS • • • Distributed Power Systems Battery Chargers Pre-Regulator for Linear Regulators “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. Board Number Dimensions EV2355DN-00A 2.0”X x 1.3”Y x 0.5”Z TYPICAL APPLICATION INPUT 4.75V to 23V 10nF 8 1 3 2 VIN BST LX RUN MP2355 SS FB GND 10nF 5 95 4 6 D1 B330A OUTPUT 3.3V / 3A COMP 4.7nF VOUT=5.0V 90 7 EFFICIENCY (%) OPEN AUTOMATIC STARTUP Efficiency vs Load Current 85 80 VOUT=3.3V VOUT=2.5V 75 70 65 60 MP2355_TAC_S01 0 500 1000 1500 2000 2500 3000 3500 LOAD CURRENT (mA) MP2355_EC01 MP2355 Rev. 1.5 9/21/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 1 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER ABSOLUTE MAXIMUM RATINGS (1) PACKAGE REFERENCE TOP VIEW SS 1 8 RUN BST 2 7 COMP VIN 3 6 FB LX 4 5 GND EXPOSED PAD ON BACKSIDE CONNECT TO PIN 5 MP2355_PD01-SOIC8N Supply Voltage VIN ....................... –0.3V to +25V Switch Voltage VLX ....................... –0.3V to +26V Boost Voltage VBST ..........VLX – 0.3V to VLX + 6V All Other Pins................................. –0.3V to +6V Junction Temperature...............................150°C Lead Temperature ....................................260°C Storage Temperature .............–65°C to +150°C Recommended Operating Conditions Input Voltage VIN ............................ 4.75V to 23V Operating Temperature .............–40°C to +85°C Thermal Resistance Part Number* MP2355DN * Package SOIC8N (Exposed Pad) Temperature –40°C to +85°C For Tape & Reel, add suffix –Z (eg. MP2355DN–Z) For RoHS compliant packaging, add suffix –LF (eg. MP2355DN –LF–Z) (2) (3) θJA θJC SOIC8N .................................. 50 ...... 10... °C/W Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1” square of 1 oz copper. ELECTRICAL CHARACTERISTICS VIN = 12V, TA = +25°C, unless otherwise noted. Parameter Shutdown Supply Current Supply Current Symbol Condition VRUN = 0V VRUN = 2.8, VFB = 1.5V Feedback Voltage VFB Error Amplifier Voltage Gain Error Amplifier Transconductance High-Side Switch-On Resistance Low-Side Switch-On Resistance High-Side Switch Leakage Current Current Limit (4) Current Sense to COMP Transconductance Oscillation Frequency Short Circuit Oscillation Frequency Maximum Duty Cycle Minimum Duty Cycle EN Shutdown Threshold Voltage AVEA MP2355 Rev. 1.5 9/21/2007 GEA 4.75V ≤ VIN ≤ 23V, VCOMP < 2V Min Typ 20 1.0 Max 30 1.2 Units μA mA 1.194 1.222 1.250 V 400 ΔICOMP = ±10μA 500 800 V/V 1120 μA/V RDS(ON)1 95 mΩ RDS(ON)2 10 Ω VRUN = 0V, VLX = 0V 0 3.7 GCS fS VFB = 0V DMAX DMIN 10 μA 4.3 A 3.8 A/V 330 380 430 KHz 20 35 50 KHz 0 % % 1.5 V VFB = 1.0V VFB = 1.5V 90 0.9 1.2 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 2 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS (continued) VIN = 12V, TA = +25°C, unless otherwise noted. Parameter Enable Pull Up Current EN UVLO Threshold EN UVLO Threshold Hysteresis Soft-Start Period Symbol Condition VRUN = 0V VEN Rising Min 1.1 2.37 Typ 1.8 2.54 CSS = 0.1μF Thermal Shutdown Max 2.5 2.71 Units μA V 210 mV 10 ms 150 °C Note: 4) Equivalent output current = 1.5A ≥ 50% Duty Cycle 2.0A ≤ 50% Duty Cycle Assumes ripple current = 30% of load current. Slope compensation changes current limit above 40% duty cycle. TYPICAL PERFORMANCE CHARACTERISTICS Circuit of Figure 2, VIN = 12V, VO = 3.3V, L1 = 15µH, C1 = 10µF, C2 = 22µF, TA = +25°C, unless otherwise noted. Heavy Load Operation Light Load Operation 3A Load No Load VIN, AC 200mV/div. VIN, AC 20mV/div. VO, AC 20mV/div. VO, AC 20mV/div. IL 1A/div. IL 1A/div. VSW 10V/div. VSW 10V/div. MP2355-TPC01 MP2355-TPC02 Startup from Shutdown Startup from Shutdown Startup from Shutdown No C4 3A Resistive Load C4 = 10nF 3A Resistive Load C4 = 10nF No Load VEN 5V/div. VEN 5V/div. VOUT 1V/div. VOUT 1V/div. IL 1A/div. VOUT 1V/div. IL 1A/div. IL 1A/div. MP2355-TPC03 MP2355 Rev. 1.5 9/21/2007 VEN 5V/div. MP2355-TPC04 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. MP2355-TPC05 3 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) Circuit of Figure 2, VIN = 12V, VO = 3.3V, L1 = 15µH, C1 = 10µF, C2 = 22µF, TA = +25°C, unless otherwise noted. Load Transient Short Circuit Protection VO, AC 200mV/div. Short Circuit Recovery VOUT 2V/div. VOUT 2V/div. IL 1A/div. ILOAD 1A/div. IL 2A/div. IL 2A/div. MP2355-TPC06 MP2355-TPC07 MP2355-TPC08 PIN FUNCTIONS Pin # 1 2 3 4 5 6 7 8 Name Description Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to SS GND to set the soft-start period. A 0.1μF capacitor sets the soft-start period to 10ms. To disable the soft-start feature, leave SS unconnected. High-Side Gate Drive Boost Input. BST supplies the drive for the high-side N-Channel BST MOSFET switch. Connect a 10nF or greater capacitor from LX to BST to power the high side switch. Power Input. VIN supplies the power to the IC, as well as the step-down converter switches. VIN Drive VIN with a 4.75V to 23V power source. Bypass VIN to GND with a suitably large capacitor to eliminate noise on the input to the IC. See Input Capacitor Power Switching Output. LX is the switching node that supplies power to the output. LX Connect the output LC filter from LX to the output load. Note that a capacitor is required from LX to BST to power the high-side switch. GND Ground. (Note: Connect the exposed pad on backside to Pin 5.) Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a FB resistive voltage divider from the output voltage. The feedback threshold is 1.222V. See Setting the Output Voltage Compensation Node. COMP is used to compensate the regulation control loop. Connect a COMP series RC network from COMP to GND to compensate the regulation control loop. In some cases, an additional capacitor from COMP to GND is required. See Compensation Enable/UVLO. A voltage greater than 2.71V enables operation. For complete low current RUN shutdown the EN pin voltage needs to be less than 900mV. MP2355 Rev. 1.5 9/21/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 4 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER OPERATION is compared to the switch current measured internally to control the output voltage. The MP2355 is a current-mode step-down regulator. It regulates input voltages from 4.75V to 23V down to an output voltage as low as 1.222V, and is able to supply up to 3A of load current. The converter uses an internal N-Channel MOSFET switch to step-down the input voltage to the regulated output voltage. Since the MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between LX and BST drives the gate. The capacitor is internally charged while LX is low. The MP2355 uses current-mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal error amplifier. The output current of the transconductance error amplifier is presented at COMP where a network compensates the regulation control system. The voltage at COMP An internal 10Ω switch from LX to GND is used to insure that LX is pulled to GND when LX is low to fully charge the BST.capacitor. VIN 3 CURRENT SENSE AMPLIFIER INTERNAL REGULATORS OSCILLATOR 42/380kHz + 0.7V -- RUN 8 -2.37V/ 2.62V + FREQUENCY FOLDBACK COMPARATOR + SLOPE COMP 5V -- CLK + SHUTDOWN COMPARATOR -- S Q R Q CURRENT COMPARATOR 2 BST 4 LX 5 GND LOCKOUT COMPARATOR 1.8V -- + -- 0.7V 1.222V 6 FB + ERROR AMPLIFIER 7 COMP 1 SS MP2355_BD01 Figure 1—Functional Block Diagram MP2355 Rev. 1.5 9/21/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 5 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER APPLICATIONS INFORMATION C5 10nF INPUT 4.75V to 23V 3 OPEN AUTOMATIC STARTUP 8 1 2 VIN RUN FB 5 OUTPUT 3.3V / 3A 4 MP2355 SS GND C4 10nF BST LX 6 D1 B330A COMP 7 C6 OPEN C3 4.7nF MP2355_TAC_F02 Figure 2—MP2355 with Murata 22μF, 10V Ceramic Output Capacitor COMPONENT SELECTION Setting the Output Voltage The output voltage is set using a resistive voltage divider from the output voltage to FB pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio: VFB = VOUT R2 R1 + R2 Thus the output voltage is: VOUT = 1.22 × R1 + R2 R2 A good rule for determining the inductance to use is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum switch current limit. Also, make sure that the peak inductor current is below the maximum switch current limit. The inductance value can be calculated by: L= ⎛ ⎞ VOUT V × ⎜⎜1 − OUT ⎟⎟ fS × ΔIL ⎝ VIN ⎠ Where VFB is the feedback voltage and VOUT is the output voltage. Where VIN is the input voltage, fS is the 380KHz switching frequency, and ΔIL is the peak-topeak inductor ripple current. A typical value for R2 can be as high as 100kΩ, but a typical value is 10kΩ. Using that value, R1 is determined by: Choose an inductor that will not saturate under the maximum inductor peak current. The peak inductor current can be calculated by: R1 = 8.18 × ( VOUT − 1.22)(kΩ ) For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is 17kΩ. Inductor The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. However, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturation current. MP2355 Rev. 1.5 9/21/2007 ILP = ILOAD + ⎛ VOUT V × ⎜1 − OUT 2 × f S × L ⎜⎝ VIN ⎞ ⎟⎟ ⎠ Where ILOAD is the load current. Table 1 lists a number of suitable inductors from various manufacturers. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI requirement. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 6 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER Table 1—Inductor Selection Guide Vendor/ Model Package Dimensions (mm) Core Type Core Material W L H Open Ferrite 7.0 7.8 5.5 Sumida CR75 CDH74 Open Ferrite 7.3 8.0 5.2 CDRH5D28 Shielded Ferrite 5.5 5.7 5.5 CDRH5D28 Shielded Ferrite 5.5 5.7 5.5 Sumida (continued) CDRH6D28 Shielded Ferrite 6.7 6.7 3.0 CDRH104R Shielded Ferrite 10.1 10.0 3.0 Input Capacitor The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current to the step-down converter while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors may also suffice. Since the input capacitor (C1) absorbs the input switching current it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: I C1 = ILOAD × Toko D53LC Type A Shielded Ferrite 5.0 5.0 3.0 D75C Shielded Ferrite 7.6 7.6 5.1 D104C Shielded Ferrite 10.0 10.0 4.3 D10FL Open Ferrite 9.7 1.5 4.0 DO3308 Open Ferrite 9.4 13.0 3.0 DO3316 Open Ferrite 9.4 13.0 5.1 Choose a diode which has a maximum reverse voltage rating is greater than the maximum input voltage, and who’s current rating is greater than the maximum load current. Table 2 lists example Schottky diodes and manufacturers. Table 2—Diode Selection Guide Diode SK33 SK34 B330 B340 MBRS330 MBRS340 MP2355 Rev. 1.5 9/21/2007 ⎞ ⎟ ⎟ ⎠ The worst-case condition occurs at VIN = 2VOUT, where: I C1 = Coilcraft Output Rectifier Diode The output rectifier diode supplies the current to the inductor when the high-side switch is off. To reduce losses due to the diode forward voltage and recovery times, use a Schottky diode. VOUT ⎛⎜ VOUT × 1− VIN ⎜⎝ VIN ILOAD 2 For simplification, choose the input capacitor whose RMS current rating greater than half of the maximum load current. The input capacitor can be electrolytic, tantalum or ceramic. When using electrolytic or tantalum capacitors, a small, high quality ceramic capacitor, i.e. 0.1μF, should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple caused by capacitance can be estimated by: ΔVIN = ⎛ ILOAD V V × OUT × ⎜⎜ 1 − OUT f s × C1 VIN VIN ⎝ ⎞ ⎟⎟ ⎠ Voltage/Current Manufacture Rating 30V, 3A 40V, 3A 30V, 3A 40V, 3A 30V, 3A 40V, 3A Diodes Inc. Diodes Inc. Diodes Inc. Diodes Inc. On Semiconductor On Semiconductor www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 7 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER Output Capacitor The output capacitor is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: ΔVOUT = VOUT ⎛ V × ⎜⎜1 − OUT fS × L ⎝ VIN ⎞ ⎞ ⎛ 1 ⎟ ⎟⎟ × ⎜ R ESR + ⎜ 8 × f S × C2 ⎟⎠ ⎠ ⎝ Where L is the inductor value, C2 is the output capacitance value, and RESR is the equivalent series resistance (ESR) value of the output capacitor. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by: ΔVOUT = ⎛ V × ⎜⎜1 − OUT VIN × L × C2 ⎝ VOUT 8 × fS 2 ⎞ ⎟⎟ ⎠ In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: ΔVOUT = VOUT ⎛ V × ⎜⎜1 − OUT fS × L ⎝ VIN ⎞ ⎟⎟ × R ESR ⎠ The characteristics of the output capacitor also affect the stability of the regulation system. The MP2355 can be optimized for a wide range of capacitance and ESR values. Compensation Components MP2355 employs current mode control for easy compensation and fast transient response. The system stability and transient response are controlled through the COMP pin. COMP pin is the output of the internal transconductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to control the characteristics of the control system. The DC gain of the voltage feedback loop is given by: A VDC = R LOAD × G CS × A VEA × Where AVEA is the error amplifier voltage gain, is the current sense 400V/V; GCS transconductance, 3.8A/V; RLOAD is the load resistor value. The system has two poles of importance. One is due to the compensation capacitor (C3) and the output resistor of error amplifier, and the other is due to the output capacitor and the load resistor. These poles are located at: fP1 = GEA 2π × C3 × A VEA fP2 = 1 2π × C2 × R LOAD Where GEA is the transconductance, 800μA/V. error amplifier The system has one zero of importance, due to the compensation capacitor (C3) and the compensation resistor (R3). This zero is located at: f Z1 = 1 2π × C3 × R3 The system may have another zero of importance, if the output capacitor has a large capacitance and/or a high ESR value. The zero, due to the ESR and capacitance of the output capacitor, is located at: fESR = 1 2π × C2 × RESR In this case (as shown in Figure 2), a third pole set by the compensation capacitor (C6) and the compensation resistor (R3) is used to compensate the effect of the ESR zero on the loop gain. This pole is located at: f P3 = MP2355 Rev. 1.5 9/21/2007 VFB VOUT 1 2π × C6 × R3 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 8 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER The goal of compensation design is to shape the converter transfer function to get a desired loop gain. The system crossover frequency where the feedback loop has the unity gain is important. Lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies could cause system unstable. A good rule of thumb is to set the crossover frequency to approximately one-tenth of the switching frequency. Switching frequency for the MP2355 is 380KHz, so the desired crossover frequency is around 38KHz. Table 3 lists the typical values of compensation components for some standard output voltages with various output capacitors and inductors. The values of the compensation components have been optimized for fast transient responses and good stability at given conditions. Table 3—Compensation Values for Typical Output Voltage/Capacitor Combinations VOUT L1 C2 R3 C3 C6 2.5V 10μH min. 22μF Ceramic 3.9kΩ 5.6nF None 3.3V 15μH min. 22μF Ceramic 4.7kΩ 4.7nF None 5V 15μH min. 22μF Ceramic 7.5kΩ 2.7nF None 12V 22μH min. 22μF Ceramic 15kΩ 1.5nF None 2.5V 10μH min. 560μF Al. 30mΩ ESR 100kΩ 1nF 150pF 3.3V 15μH min. 560μF Al 30mΩ ESR 120kΩ 1nF 120pF 5V 15μH min. 470μF Al. 30mΩ ESR 150kΩ 1nF 82pF 12V 22μH min. 220μF Al. 30mΩ ESR 169kΩ 1nF 39pF To optimize the compensation components for conditions not listed in Table 2, the following procedure can be used. 1) Choose the compensation resistor (R3) to set the desired crossover frequency. Determine the R3 value by the following equation: 2π × C2 × f C VOUT R3 = × G EA × G CS VFB MP2355 Rev. 1.5 9/21/2007 2) Choose the compensation capacitor (C3) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero, fZ1, to less than one forth of the crossover frequency provides sufficient phase margin. Determine the C3 value by the following equation: C3 > 4 2π × R3 × f C Where R3 is the compensation resistor value and fC is the desired crossover frequency, 38KHz. 3) Determine if the second compensation capacitor (C6) is required. It is required if the ESR zero of the output capacitor is located at less than half of the 380KHz switching frequency, or the following relationship is valid: f 1 < S 2π × C2 × R ESR 2 If this is the case, then add the second compensation capacitor (C6) to set the pole fP3 at the location of the ESR zero. Determine the C6 value by the equation: C6 = C2 × R ESR R3 External Bootstrap Diode It is recommended that an external bootstrap diode be added when the system has a 5V fixed input or the power supply generates a 5V output. This helps improve the efficiency of the regulator. The bootstrap diode can be a low cost one such as IN4148 or BAT54. 5V BS 10nF MP2355 SW MP2355_F03 Figure 3—External Bootstrap Diode This diode is also recommended for high duty cycle operation (when VOUT >65%) and high VIN output voltage (VOUT>12V) applications. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 9 MP2355 – 3A, 23V, 380KHz STEP-DOWN CONVERTER PACKAGE INFORMATION SOIC8N (EXPOSED PAD) 0.229(5.820) 0.244(6.200) PIN 1 IDENT. NOTE 4 0.150(3.810) 0.157(4.000) 0.0075(0.191) 0.0098(0.249) SEE DETAIL "A" NOTE 2 0.011(0.280) x 45o 0.020(0.508) 0.013(0.330) 0.020(0.508) 0.050(1.270)BSC 0o-8o NOTE 3 0.189(4.800) 0.197(5.000) 0.053(1.350) 0.068(1.730) DETAIL "A" 0.016(0.410) 0.050(1.270) .050 0.049(1.250) 0.060(1.524) .028 0.200 (5.07 mm) SEATING PLANE 0.001(0.030) 0.004(0.101) 0.140 (3.55mm) 0.060 Land Pattern NOTE: 1) Control dimension is in inches. Dimension in bracket is millimeters. 2) Exposed Pad Option (N-Package) ; 2.31mm -2.79mm x 2.79mm - 3.81mm. Recommend Solder Board Area: 2.80mm x 3.82mm = 10.7mm 2 (16.6 mil2) 3) The length of the package does not include mold flash. Mold flash shall not exceed 0.006in. (0.15mm) per side. With the mold flash included, over-all length of the package is 0.2087in. (5.3mm) max. 4) The width of the package does not include mold flash. Mold flash shall not exceed 0.10in. (0.25mm) per side. With the mold flash included, over-all width of the package is 0.177in. (4.5mm) max. NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP2355 Rev. 1.5 9/21/2007 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2007 MPS. All Rights Reserved. 10