Order Now Product Folder Support & Community Tools & Software Technical Documents LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 LMZ10503 3-A SIMPLE SWITCHER(R) Power Module With 5.5-V Maximum Input Voltage 1 Features 2 Applications * * * 1 * * * * * * Integrated Shielded Inductor Flexible Start-up Sequencing Using External Soft Start, Tracking, and Precision Enable Protection Against In-Rush Currents and Faults Such as Input UVLO and Output Short Circuit Single Exposed Pad and Standard Pinout for Easy Mounting and Manufacturing Pin-to-Pin Compatible With - LMZ10504 (4 A / 20 W Maximum) - LMZ10505 (5 A / 25 W Maximum) Electrical Specifications - 15-W Maximum Total Output Power - Up to 3-A Output Current - Input Voltage Range 2.95 V to 5.5 V - Output Voltage Range 0.8 V to 5 V - 1.63% Feedback Voltage Accuracy Over Temperature Performance Benefits - Operates at High Ambient Temperatures - High Efficiency up to 96% Reduces System Heat Generation - Low Radiated Emissions (EMI) Tested to EN55022 Class B Standard (EN 55022:2006, +A1:2007, FCC Part 15 Subpart B: 2007. See Table 9 and layout information for more regarding device under test.) - Fast Transient Response for Powering FPGAs and ASICs Create a Custom Design Using the LMZ10503 With the WEBENCH(R) Power Designer * * Point-of-Load Conversions From 3.3-V and 5-V Rails Space-Constrained Applications Noise Sensitive Applications (that is, Transceiver, Medical) 3 Description The LMZ10503 SIMPLE SWITCHER power module is a complete, easy-to-use DC-DC solution capable of driving up to a 3-A load with exceptional power conversion efficiency, output voltage accuracy, line and load regulation. The LMZ10503 is available in an innovative package that enhances thermal performance and allows for hand or machine soldering. The LMZ10503 can accept an input voltage rail between 2.95 V and 5.5 V and can deliver an adjustable and highly accurate output voltage as low as 0.8 V. One megahertz fixed-frequency PWM switching provides a predictable EMI characteristic. Two external compensation components can be adjusted to set the fastest response time, while allowing the option to use ceramic and/or electrolytic output capacitors. Externally programmable soft-start capacitor facilitates controlled startup. The LMZ10503 is a reliable and robust solution with the following features: lossless cycle-by-cycle peak current limit to protect for over current or short-circuit fault, thermal shutdown, input undervoltage lockout, and prebiased start-up. Device Information(1)(2) PART NUMBER LMZ10503 PACKAGE BODY SIZE (NOM) TO-PMOD (7) 10.16 mm x 9.85 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. (2) Peak reflow temperature equals 245C. See Design Summary LMZ1xxx and LMZ2xxx Power Module Family (SNAA214) for more details. Typical Application Circuit VIN VOUT 1 VIN Cin 2 6, 7 LMZ10503 FB EN SS CO 5 GND 4, EP 3 Efficiency VOUT = 3.3 V VOUT Rfbt CSS Rcomp Ccomp Rfbb 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 4 6.1 6.2 6.3 6.4 6.5 6.6 4 4 4 4 5 7 Detailed Description ............................................ 10 7.1 7.2 7.3 7.4 8 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Overview ................................................................. Functional Block Diagram ....................................... Feature Description................................................. Device Functional Modes........................................ 10 10 10 13 Application and Implementation ........................ 14 8.1 Application Information............................................ 14 8.2 Typical Application .................................................. 14 8.3 System Examples ................................................... 20 9 Power Supply Recommendations...................... 23 10 Layout................................................................... 23 10.1 Layout Guidelines ................................................. 10.2 Layout Examples................................................... 10.3 Estimate Power Dissipation and Thermal Considerations ......................................................... 10.4 Power Module SMT Guidelines ............................ 23 24 26 27 11 Device and Documentation Support ................. 28 11.1 11.2 11.3 11.4 11.5 11.6 11.7 Device Support...................................................... Documentation Support ........................................ Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 28 28 28 28 29 29 29 12 Mechanical, Packaging, and Orderable Information ........................................................... 29 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision J (September 2015) to Revision K Page * Changed language of WEBENCH list item; added additional content and links for WEBENCH further in data sheet ......... 1 * Changed equation 1 in Enable and UVLO .......................................................................................................................... 10 Changes from Revision I (October 2013) to Revision J Page * Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1 * Removed Easy-To-Use PFM 7-Pin Package image ............................................................................................................. 1 Changes from Revision H (April 2013) to Revision I Page * Deleted 10 mils....................................................................................................................................................................... 4 * Changed 10 mils................................................................................................................................................................... 23 * Added Power Module SMT Guidelines................................................................................................................................. 27 2 Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 5 Pin Configuration and Functions NDW Package 7-Lead TO-PMOD Top View Exposed Pad Connect to GND 7 VOUT 6 VOUT 5 FB 4 GND 3 SS 2 EN 1 VIN Pin Functions PIN NAME NO. TYPE DESCRIPTION EN 2 Analog Active-high enable input for the device. Exposed Pad -- Ground Exposed pad is used as a thermal connection to remove heat from the device. Connect this pad to the PCB ground plane in order to reduce thermal resistance value. EP must also provide a direct electrical connection to the input and output capacitors ground terminals. Connect EP to pin 4. FB 5 Analog Feedback pin. This is the inverting input of the error amplifier used for sensing the output voltage. Keep the copper area of this node small. GND 4 Ground Power ground and signal ground. Provide a direct connection to the EP. Place the bottom feedback resistor as close as possible to GND and FB pin. SS 3 Analog Soft-start control pin. An internal 2-A current source charges an external capacitor connected between SS and GND pins to set the output voltage ramp rate during startup. The SS pin can also be used to configure the tracking feature. VIN 1 Power Power supply input. A low ESR input capacitance should be located as close as possible to the VIN pin and exposed pad (EP). 6, 7 Power The output terminal of the internal inductor. Connect the output filter capacitor between VOUT pin and EP. VOUT Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 3 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) (2) (3) VIN, VOUT, EN, FB, SS to GND Power Dissipation MIN MAX UNIT -0.3 6 V Internally Limited Junction Temperature 150 C Peak Reflow Case Temperature (30 sec) 245 C 150 C Storage Temperature, Tstg (1) (2) (3) -65 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. For soldering specifications, refer to the Absolute Maximum Ratings for Soldering (SNOA549). If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. 6.2 ESD Ratings V(ESD) (1) Electrostatic discharge VALUE UNIT 2000 V Human body model (HBM) (1) The human body model is a 100-pF capacitor discharged through a 1.5-k resistor into each pin. Test method is per JESD22-AI14S. 6.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) MIN MAX UNIT VIN to GND 2.95 5.5 V Junction Temperature (TJ) -40 125 C 6.4 Thermal Information LMZ10503 THERMAL METRIC (1) NDW (TO-PMOD) UNIT 7 PINS (2) RJA Junction-to-ambient thermal resistance RJC(top) Junction-to-case (top) thermal resistance (1) (2) 4 20 C/W 1.9 C/W For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report. RJA measured on a 2.25-in x 2.25-in (5.8 cm x 5.8 cm) 4-layer board, with 1-oz. copper, thirty six thermal vias, no air flow, and 1-W power dissipation. Refer to Layout or Evaluation Board Application Note AN-2024 LMZ1420x / LMZ1200x Evaluation Board (SNVA422). Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 6.5 Electrical Characteristics Specifications are for TJ = 25C unless otherwise specified. Minimum and maximum limits are ensured through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25C, and are provided for reference purposes only. VIN = VEN = 3.3 V, unless otherwise indicated in the conditions column. PARAMETER MIN (1) TEST CONDITIONS TYP (2) MAX (1) UNIT SYSTEM PARAMETERS V FB Total Feedback Voltage VIN = 2.95 V to 5.5 V Variation Including Line and VOUT = 2.5 V Load Regulation IOUT = 0 A to 3 A V FB VIN = 3.3 V, VOUT = 2.5 Feedback Voltage Variation V IOUT = 0 A V FB VIN = 3.3 V, VOUT = 2.5 Feedback Voltage Variation V IOUT = 3 A 0.8 over the operating junction temperature range TJ of -40C to 125C 0.78 V 0.82 0.8 over the operating junction temperature range TJ of -40C to 125C 0.787 over the operating junction temperature range TJ of -40C to 125C 0.785 V 0.812 0.798 V 0.81 2.6 VIN(UVLO) ISS Rising over the operating junction temperature range TJ of -40C to 125C Falling over the operating junction temperature range TJ of -40C to 125C Input UVLO Threshold (Measured at VIN pin) Soft-Start Current V 2.95 2.4 1.95 Charging Current IQ Non-Switching Input Current ISD Shutdown Quiescent Current IOCL Output Current Limit (Average Current) VOUT = 2.5 V fFB Frequency Fold-back In current limit 2 A 1.7 mA over the operating junction temperature range TJ of -40C to 125C VFB = 1 V 3 260 VIN = 5.5 V, VEN = 0 V over the operating junction temperature range TJ of -40C to 125C A 500 5.2 over the operating junction temperature range TJ of -40C to 125C 3.8 A 6.7 250 kHz PWM SECTION 1000 fSW Switching Frequency Drange PWM Duty Cycle Range kHz over the operating junction temperature range TJ of -40C to 125C 750 1160 over the operating junction temperature range TJ of -40C to 125C 0% 100% ENABLE CONTROL 1.23 VEN-IH EN Pin Rising Threshold over the operating junction temperature range TJ of -40C to 125C VEN-IF EN Pin Falling Threshold over the operating junction temperature range TJ of -40C to 125C V 1.8 1.06 (1) (2) V 0.8 Minimum and maximum limits are 100% production tested at an ambient temperature (TA) of 25C. Limits over the operating temperature range are ensured through correlation using Statistical Quality Control (SQC) methods. Limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25C and represent the most likely parametric norm. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 5 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com Electrical Characteristics (continued) Specifications are for TJ = 25C unless otherwise specified. Minimum and maximum limits are ensured through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25C, and are provided for reference purposes only. VIN = VEN = 3.3 V, unless otherwise indicated in the conditions column. PARAMETER TEST CONDITIONS MIN (1) TYP (2) MAX (1) UNIT THERMAL CONTROL TSD TJ for Thermal Shutdown TSD-HYS Hysteresis for Thermal Shutdown 145 C 10 C 7 mVpk- PERFORMANCE PARAMETERS VOUT Output Voltage Ripple Refer to Table 1 VOUT = 2.5 V Bandwidth Limit = 2 MHz VOUT Output Voltage Ripple Refer to Table 5 Bandwidth Limit = 20 MHz VFB / VFB Feedback Voltage Line Regulation VIN = 2.95 V to 5.5 V IOUT = 0 A 0.04% VOUT / VOUT Output Voltage Line Regulation VIN = 2.95 V to 5.5 V IOUT = 0 A, VOUT = 2.5 V 0.04% VFB / VFB Feedback Voltage Load Regulation IOUT = 0 A to 3 A VOUT / VOUT Output Voltage Load Regulation IOUT = 0 A to 3 A VOUT = 2.5 V 0.25% VOUT = 3.3 V 96.3% VOUT = 2.5 V 94.9% VOUT = 1.8 V 93.3% VOUT = 1.5 V 92.2% VOUT = 1.2 V 90.5% VOUT = 0.8 V 86.9% VOUT = 2.5 V 95.7% pk 5 mVpkpk 0.25% EFFICIENCY 6 Peak Efficiency (1 A) VIN = 5V Peak Efficiency (1 A) VIN = 3.3 V Full Load Efficiency (3 A) VIN = 5 V Full Load Efficiency (3 A) VIN = 3.3 V VOUT = 1.8 V 94% VOUT = 1.5 V 92.9% VOUT = 1.2 V 91.3% VOUT = 0.8 V 87.9% VOUT = 3.3 V 94.8% VOUT = 2.5 V 93% VOUT = 1.8 V 90.8% VOUT = 1.5 V 89.3% VOUT = 1.2 V 87.1% VOUT = 0.8 V 82.3% VOUT = 2.5 V 92.4% VOUT = 1.8 V 89.8% VOUT = 1.5 V 88.2% VOUT = 1.2 V 85.9% VOUT = 0.8 V 80.8% Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 6.6 Typical Characteristics Unless otherwise specified, the following conditions apply: VIN = VEN = 5 V, CIN is 47 F 10-V X5R ceramic capacitor; TA = 25C for efficiency curves and waveforms. VOUT = 3.3 V VOUT = 2.5 V Figure 1. Efficiency VOUT = 1.8 V Figure 2. Efficiency VOUT = 1.5 V Figure 3. Efficiency Figure 4. Efficiency VOUT = 0.8 V VOUT = 1.2 V Figure 6. Efficiency Figure 5. Efficiency Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 7 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com Typical Characteristics (continued) Unless otherwise specified, the following conditions apply: VIN = VEN = 5 V, CIN is 47 F 10-V X5R ceramic capacitor; TA = 25C for efficiency curves and waveforms. VIN = 5 V, RJA = 20C/W VIN = 3.3 V, RJA = 20C/W Figure 7. Current Derating Figure 8. Current Derating VOUT = 2.5 V, IOUT = 0 A VIN = 5 V, VOUT = 2.5 V, IOUT = 3 A Figure 10. Start-Up Figure 9. Radiated Emissions (EN55022, Class B) Evaluation Board VOUT = 2.5 V, IOUT = 0 A VIN = 3.3 V, VOUT = 2.5 V, IOUT = 0.3 A to 2.7 A to 0.3-A Step 20-MHz Bandwidth Limited. Refer to Table 5 for BOM, includes optional components Figure 11. Prebiased Start-Up 8 Figure 12. Load Transient Response Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 Typical Characteristics (continued) Unless otherwise specified, the following conditions apply: VIN = VEN = 5 V, CIN is 47 F 10-V X5R ceramic capacitor; TA = 25C for efficiency curves and waveforms. VIN = 5 V, VOUT = 2.5 V, IOUT = 0.3 A to 2.7 A to 0.3-A step 20-MHz Bandwidth Limited. Refer to Table 5 for BOM, includes optional components VIN = 3.3 V, VOUT = 2.5 V, IOUT = 3 A, 20 mV/DIV. Refer to Table 5 for BOM Figure 13. Load Transient Response Figure 14. Output Voltage Ripple VIN = 5 V, VOUT = 2.5 V, IOUT = 3 A, 20 mV/DIV. Refer to Table 5 for BOM Figure 15. Output Voltage Ripple Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 9 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 7 Detailed Description 7.1 Overview The LMZ10503 SIMPLE SWITCHER power module is a complete, easy-to-use DC-DC solution capable of driving up to a 3-A load with exceptional power conversion efficiency, output voltage accuracy, line and load regulation. The LMZ10503 is available in an innovative package that enhances thermal performance and allows for hand or machine soldering. The LMZ10503 is a reliable and robust solution with the following features: lossless cycle-by-cycle peak current limit to protect for overcurrent or short-circuit fault, thermal shutdown, input undervoltage lockout, and prebiased start-up. 7.2 Functional Block Diagram VIN 1 1: SS 5 FB Drivers Voltage Mode Control 3 2.2 PF 2.2 PH 6, 7 VOUT N-MOSFET 2 EN P-MOSFET 2.2 PF 4, EP GND 7.3 Feature Description 7.3.1 Enable The LMZ10503 features an enable (EN) pin and associated comparator to allow the user to easily sequence the LMZ10503 from an external voltage rail, or to manually set the input UVLO threshold. The turnon or rising threshold and hysteresis for this comparator are typically 1.23 V and 0.15 V respectively. The precise reference for the enable comparator allows the user to ensure that the LMZ10503 will be disabled when the system demands it to be. The EN pin should not be left floating. For always-on operation, connect EN to VIN. 7.3.2 Enable and UVLO Using a resistor divider from VIN to EN as shown in the schematic diagram below, the input voltage at which the part begins switching can be increased above the normal input UVLO level according to R Renb VIN(UVLO) 1.23 V u ent Renb (1) For example, suppose that the required input UVLO level is 3.69 V. Choosing Renb = 10 k, then we calculate Rent = 20 k. 10 Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 Feature Description (continued) VIN VIN LMZ10503 Rent Cin1 EN Renb GND Figure 16. Setting Enable and UVLO Alternatively, the EN pin can be driven from another voltage source to cater to system sequencing requirements commonly found in FPGA and other multi-rail applications. Figure 17 shows an LMZ10503 that is sequenced to start based on the voltage level of a master system rail (VOUT1). Master Power Supply VOUT1 VIN VOUT2 VIN VOUT Rent Cin1 LMZ10503 CO1 EN Renb GND Figure 17. Setting Enable and UVLO Using External Power Supply 7.3.3 Soft-Start The LMZ10503 begins to operate when both the VIN and EN, voltages exceed the rising UVLO and enable thresholds, respectively. A controlled soft-start eliminates inrush currents during start-up and allows the user more control and flexibility when sequencing the LMZ10503 with other power supplies. In the event of either VIN or EN decreasing below the falling UVLO or enable threshold respectively, the voltage on the soft-start pin is collapsed by discharging the soft-start capacitor by a 14-A (typical) current sink to ground. 7.3.4 Soft-Start Capacitor Determine the soft-start capacitance with the following relationship: t ss u Iss CSS VFB where * VFB is the internal reference voltage (nominally 0.8 V), ISS is the soft-start charging current (nominally 2 A) and CSS is the external soft-start capacitance. (2) Thus, the required soft-start capacitor per unit output voltage startup time is given by: CSS 2.5 nF / ms (3) For example, a 4-ms soft-start time will yield a 10-nF capacitance. The minimum soft-start capacitance is 680 pF. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 11 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com Feature Description (continued) 7.3.5 Tracking The LMZ10503 can track the output of a master power supply during soft-start by connecting a resistor divider to the SS pin. In this way, the output voltage slew rate of the LMZ10503 will be controlled by a master supply for loads that require precise sequencing. When the tracking function is used, a small value soft-start capacitor should be connected to the SS pin to alleviate output voltage overshoot when recovering from a current limit fault. Master Power Supply VOUT1 VIN VOUT2 VIN VOUT Rtrkt Cin1 EN LMZ10503 CO1 SS VSS Rtrkb GND Figure 18. Tracking Using External Power Supply 7.3.6 Tracking - Equal Soft-Start Time One way to use the tracking feature is to design the tracking resistor divider so that the master supply output voltage, VOUT1, and the LMZ10503 output voltage, VOUT2, both rise together and reach their target values at the same time. This is termed ratiometric start-up. For this case, the equation governing the values of tracking divider resistors Rtrkb and Rtrkt is given by: R trkt R trkb VOUT1 1.0 V (4) Equation 4 includes an offset voltage, of 200 mV, to ensure that the final value of the SS pin voltage exceeds the reference voltage of the LMZ10503. This offset will cause the LMZ10503 output voltage to reach regulation slightly before the master supply. A value of 33 k 1% is recommended for Rtrkt as a compromise between high precision and low quiescent current through the divider while minimizing the effect of the 2-A soft-start current source. For example, if the master supply voltage VOUT1 is 3.3 V and the LMZ10503 output voltage was 1.8 V, then the value of Rtrkb needed to give the two supplies identical soft-start times would be 14.3 k. Figure 19 shows an example of tracking using the equal soft-start time. RATIOMETRIC STARTUP VOUT1 VOLTAGE VOUT2 EN TIME Figure 19. Timing Diagram for Tracking Using Equal Soft-Start Time 12 Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 Feature Description (continued) 7.3.7 Tracking - Equal Slew Rates Alternatively, the tracking feature can be used to have similar output voltage ramp rates. This is referred to as simultaneous start-up. In this case, the tracking resistors can be determined based on Equation 5: 0.8 V R trkb u R trkt VOUT 2 0.8 V (5) and to ensure proper overdrive of the SS pin: VOUT 2 0.8 u VOUT1 (6) For the example case of VOUT1 = 5 V and VOUT2 = 2.5 V, with Rtrkt set to 33 k as before, Rtrkb is calculated from the above equation to be 15.5 k. Figure 20 shows an example of tracking using the equal slew rates. SIMULTANEOUS STARTUP VOUT1 VOLTAGE VOUT2 EN TIME Figure 20. Timing Diagram for Tracking Using Equal Slew Rates 7.3.8 Current Limit When a current greater than the output current limit (IOCL) is sensed, the ON-time is immediately terminated and the low-side MOSFET is activated. The low-side MOSFET stays on for the entire next four switching cycles. During these skipped pulses, the voltage on the soft-start pin is reduced by discharging the soft-start capacitor by a current sink on the soft-start pin of nominally 14 A. Subsequent overcurrent events will drain more and more charge from the soft-start capacitor, effectively decreasing the reference voltage as the output droops due to the pulse skipping. Reactivation of the soft-start circuitry ensures that when the overcurrent situation is removed, the part will resume normal operation smoothly. 7.3.9 Overtemperature Protection When the LMZ10503 senses a junction temperature greater than 145C (typical), both switching MOSFETs are turned off and the part enters a standby state. Upon sensing a junction temperature below 135C (typical), the part will re-initiate the soft-start sequence and begin switching once again. 7.4 Device Functional Modes 7.4.1 Prebias Start-Up Capability At start-up, the LMZ10503 is in a prebiased state when the output voltage is greater than zero. This often occurs in many multi-rail applications such as when powering an ASIC, FPGA, or DSP. The output can be prebiased in these applications through parasitic conduction paths from one supply rail to another. Even though the LMZ10503 is a synchronous converter, it will not pull the output low when a prebias condition exists. The LMZ10503 will not sink current during start-up until the soft-start voltage exceeds the voltage on the FB pin. Because the device does not sink current it protects the load from damage that might otherwise occur if current is conducted through the parasitic paths of the load. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 13 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI's customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information The LMZ10503 is a step-down DC-to-DC power module. It is typically used to convert a higher DC voltage to a lower DC voltage with a maximum output current of 3 A. The following design procedure can be used to select components for the LMZ10503. Alternately, the WEBENCH software may be used to generate complete designs. When generating a design, the WEBENCH software uses iterative design procedure and accesses comprehensive databases of components. Please go to www.ti.com for more details. 8.2 Typical Application VIN VOUT 1 LMZ10503 VIN Cin 2 VOUT 6, 7 FB EN SS CO 5 GND 4, EP 3 Rfbt CSS Rcomp Ccomp Rfbb Figure 21. Typical Application Circuit 8.2.1 Design Requirements For this example the following application parameters exist. * VIN = 5 V * VOUT = 2.5 V * IOUT = 3 A * VOUT = 20 mVpk-pk * Vo_tran = 20 mVpk-pk Table 1. Bill of Materials, VIN = 3.3 V to 5 V, VOUT = 2.5 V, IOUT (MAX) = 3 A, Optimized for Electrolytic Input and Output Capacitance DESIGNATOR DESCRIPTION CASE SIZE MANUFACTURER MANUFACTURER P/N QUANTITY U1 SIMPLE SWITCHER PFM-7 Texas Instruments LMZ10503 1 Cin1 150 F, 6.3 V, 18 m C2, 6.0 x 3.2 x 1.8 mm Sanyo 6TPE150MIC2 1 330 F, 6.3 V, 18 m D3L, 7.3 x 4.3 x 2.8 mm Sanyo 6TPE330MIL 1 CO1 14 Rfbt 100 k 0603 Vishay Dale CRCW0603100KFKEA 1 Rfbb 47.5 k 0603 Vishay Dale CRCW060347K5FKEA 1 Rcomp 15 k 0603 Vishay Dale CRCW060315K0FKEA 1 Ccomp 330 pF, 5%, C0G, 50 V 0603 TDK C1608C0G1H331J 1 CSS 10 nF, 10%, X7R, 16 V 0603 Murata GRM188R71C103KA01 1 Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 Table 2. Bill of Materials, VIN = 3.3 V, VOUT = 0.8 V, IOUT (MAX) = 3 A, Optimized for Solution Size and Transient Response DESIGNATOR DESCRIPTION CASE SIZE MANUFACTURER MANUFACTURER P/N QUANTITY U1 SIMPLE SWITCHER PFM-7 Texas Instruments LMZ10503TZ 1 Cin1, CO1 47 F, X5R, 6.3 V 1206 TDK C3216X5R0J476M 2 Rfbt 110 k 0402 Vishay Dale CRCW0402100KFKED 1 Rcomp 1.0 k 0402 Vishay Dale CRCW04021K00FKED 1 Ccomp 27 pF, 5%, C0G, 50 V 0402 Murata GRM1555C1H270JZ01 1 CSS 10 nF, 10%, X7R, 16 V 0402 Murata GRM155R71C103KA01 1 8.2.2 Detailed Design Procedure LMZ10503 is fully supported by WEBENCH and offers the following: component selection, performance, electrical, and thermal simulations as well as the Build-It board, for a reduced design time. On the other hand, all external components can be calculated by following the design procedure below. 1. Determine the input voltage and output voltage. Also, make note of the ripple voltage and voltage transient requirements. 2. Determine the necessary input and output capacitance. 3. Calculate the feedback resistor divider. 4. Select the optimized compensation component values. 5. Estimate the power dissipation and board thermal requirements. 6. Follow the PCB design guideline. 7. Learn about the LMZ10503 features such as enable, input UVLO, soft start, tracking, prebiased start-up, current limit, and thermal shutdown. 8.2.2.1 Custom Design With WEBENCH(R) Tools Click here to create a custom design using the LMZ10503 device with the WEBENCH(R) Power Designer. 1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements. 2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. Compare the generated design with other possible solutions from Texas Instruments. The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability. In most cases, these actions are available: * Run electrical simulations to see important waveforms and circuit performance * Run thermal simulations to understand board thermal performance * Export customized schematic and layout into popular CAD formats * Print PDF reports for the design, and share the design with colleagues Get more information about WEBENCH tools at www.ti.com/WEBENCH. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 15 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 8.2.2.2 Input Capacitor Selection A 22-F or 47-F, high-quality dielectric (X5R, X7R) ceramic capacitor rated at twice the maximum input voltage is typically sufficient. The input capacitor must be placed as close as possible to the VIN pin and GND exposed pad to substantially eliminate the parasitic effects of any stray inductance or resistance on the PCB and supply lines. Neglecting capacitor equivalent series resistance (ESR), the resultant input capacitor AC ripple voltage is a triangular waveform. The minimum input capacitance for a given peak-to-peak value (VIN) of VIN is specified as follows: I u Du (1 D) Cin t OUT fsw u ' VIN where * D the PWM duty cycle, D, is given by Equation 8: (7) VOUT VIN (8) If VIN is 1% of VIN, this equals to 50 mV and fSW = 1 MHz. 2.5 V * 2.5 V * 3 Au u 1 5 V (c) 5V (c) t 15 P F Cin t 1 MHz u 50mV (9) A second criteria before finalizing the Cin bypass capacitor is the RMS current capability. The necessary RMS current rating of the input capacitor to a buck regulator can be estimated by: ICin(RMS) IOUT u D(1 D) ICin(RMS) 3 Au 2.5 V 2.5 V * 1 5V (c) 5 V (10) 1.5 A (11) With this high AC current present in the input capacitor, the RMS current rating becomes an important parameter. The maximum input capacitor ripple voltage and RMS current occur at 50% duty cycle. Select an input capacitor rated for at least the maximum calculated ICin(RMS). Additional bulk capacitance with higher ESR may be required to damp any resonance effects of the input capacitance and parasitic inductance. 8.2.2.3 Output Capacitor Selection In general, 22-F to 100-F, high-quality dielectric (X5R, X7R) ceramic capacitor rated at twice the maximum output voltage is sufficient given the optimal high-frequency characteristics and low ESR of ceramic dielectrics. Although, the output capacitor can also be of electrolytic chemistry for increased capacitance density. Two output capacitance equations are required to determine the minimum output capacitance. One equation determines the output capacitance (CO) based on PWM ripple voltage. The second equation determines CO based on the load transient characteristics. Select the largest capacitance value of the two. The minimum capacitance, given the maximum output voltage ripple (VOUT) requirement, is determined by Equation 12: ' iL CO t 8 u fsw u > ' VOUT ( ' iL u RESR )@ where * ' iL 16 the peak to peak inductor current ripple (iL) is equal to Equation 13: (VIN VOUT ) u D Lu fsw (12) (13) Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 RESR is the total output capacitor ESR, L is the inductance value of the internal power inductor, where L = 2.2 H, and fSW = 1 MHz. Therefore, per the design example: V (5 V 2.2 V) u 2.5 5V ' iL 568 mA 2.2 P H u 1 MHz (14) The minimum output capacitance requirement due to the PWM ripple voltage is: 568 mA CO t 8 u 1 MHzu 20 mV 568 mAu 3 m : 1/4 (15) CO t 4 P F (16) Three m is a typical RESR value for ceramic capacitors. Equation 17 provides a good first pass capacitance requirement for a load transient: Istep u VFB u Lu VIN CO t 4 u VOUT u (VIN VOUT ) u ' Vo_tran where * * * Istep is the peak-to-peak load step (for this example Istep = 10% to 90% of the maximum load) VFB = 0.8 V and Vo_tran is the maximum output voltage deviation, which is 20 mV. (17) Therefore the capacitance requirement for the given design parameters is: 2.4 Au 0.8 Vu 2.2P Hu 5 V CO t 4 u 2.5 Vu (5 V 2.5 V) u 20mV (18) CO t 42 P F (19) In this particular design the output capacitance is determined by the load transient requirements. Table 3 lists some examples of commercially available capacitors that can be used with the LMZ10503. Table 3. Recommended Output Filter Capacitors CO (F) VOLTAGE (V), RESR (m) MAKE MANUFACTURER PART NUMBER CASE SIZE 22 6.3, < 5 Ceramic, X5R TDK C3216X5R0J226M 1206 47 6.3, < 5 Ceramic, X5R TDK C3216X5R0J476M 1206 47 6.3, < 5 Ceramic, X5R TDK C3225X5R0J476M 1210 47 10.0, < 5 Ceramic, X5R TDK C3225X5R1A476M 1210 100 6.3, < 5 Ceramic, X5R TDK C3225X5R0J107M 1210 100 6.3, 50 Tantalum AVX TPSD157M006#0050 D, 7.5 x 4.3 x 2.9 mm 100 6.3, 25 Organic Polymer Sanyo 6TPE100MPB2 B2, 3.5 x 2.8 x 1.9 mm 150 6.3, 18 Organic Polymer Sanyo 6TPE150MIC2 C2, 6.0 x 3.2 x 1.8 mm 330 6.3, 18 Organic Polymer Sanyo 6TPE330MIL D3L, 7.3 x 4.3 x 2.8 mm 470 6.3, 23 Niobium Oxide AVX NOME37M006#0023 E, 7.3 x 4.3 x 4.1 mm 8.2.2.3.1 Output Voltage Setting A resistor divider network from VOUT to the FB pin determines the desired output voltage as follows: R R fbb VOUT 0.8 Vu fbt R fbb (20) Rfbt is defined based on the voltage loop requirements and Rfbb is then selected for the desired output voltage. Resistors are normally selected as 0.5% or 1% tolerance. Higher accuracy resistors such as 0.1% are also available. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 17 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com The feedback voltage (at VOUT = 2.5 V) is accurate to within -2.5% / +2.5% over temperature and over line and load regulation. Additionally, the LMZ10503 contains error nulling circuitry to substantially eliminate the feedback voltage variation over temperature as well as the long term aging effects of the internal amplifiers. In addition the zero nulling circuit dramatically reduces the 1/f noise of the bandgap amplifier and reference. The manifestation of this circuit action is that the duty cycle will have two slightly different but distinct operating points, each evident every other switching cycle. 8.2.2.4 Loop Compensation The LMZ10503 preserves flexibility by integrating the control components around the internal error amplifier while using three small external compensation components from VOUT to FB. An integrated type II (two pole, one zero) voltage-mode compensation network is featured. To ensure stability, an external resistor and small value capacitor can be added across the upper feedback resistor as a pole-zero pair to complete a type III (three pole, two zero) compensation network. The compensation components recommended in Table 4 provide type III compensation at an optimal control loop performance. The typical phase margin is 45 with a bandwidth of 80 kHz. Calculated output capacitance values not listed in Table 4 should be verified before designing into production. The detailed application note AN-2013 LMZ1050x/LMZ1050xEXT SIMPLE SWITCHER Power Module (SNVA417) is available to provide verification support. In general, calculated output capacitance values below the suggested value will have reduced phase margin and higher control loop bandwidth. Output capacitance values above the suggested values will experience a lower bandwidth and increased phase margin. Higher bandwidth is associated with faster system response to sudden changes such as load transients. Phase margin changes the characteristics of the response. Lower phase margin is associated with underdamped ringing and higher phase margin is associated with overdamped response. Losing all phase margin will cause the system to be unstable; an optimized area of operation is 30 to 60 of phase margin, with a bandwidth of 100 kHz 20 kHz. VIN VOUT VIN EN Ccomp Rfbt LMZ10503 Rcomp FB GND Rfbb Figure 22. Loop Compensation Control Components Table 4. LMZ10503 Compensation Component Values VIN (V) 5 (1) 18 CO (F) ESR (m) Rfbt (k) (1) Ccomp (pF) (1) Rcomp (k) (1) MIN MAX 22 2 20 150 47 1 47 2 20 100 100 4.53 100 1 10 71.5 180 2 150 1 5 56.2 270 0.499 150 10 25 100 180 4.53 150 26 50 182 100 8.25 220 15 30 133 160 4.99 220 31 60 200 100 6.98 In the special case where the output voltage is 0.8 V, TI recommends to remove Rfbb and keep Rfbt, Rcomp, and Ccomp for a type III compensation. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 Table 4. LMZ10503 Compensation Component Values (continued) VIN (V) 3.3 CO (F) ESR (m) Rfbt (k) (1) Ccomp (pF) (1) Rcomp (k) (1) 20 100 56.2 5.62 20 76.8 120 3.32 10 49.9 220 1 MIN MAX 22 2 47 2 100 1 150 1 5 40.2 430 1 150 10 25 43.2 390 3.32 150 26 50 100 180 4.53 220 15 30 80.6 240 3.32 220 31 60 140 150 4.99 8.2.3 Application Curves VOUT = 3.3 V VOUT = 3.3 V Figure 23. Current Derating Figure 24. Efficiency Figure 25. Radiated Emissions (EN 55022, Class B) Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 19 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 8.3 System Examples 8.3.1 Application Schematic for 3.3-V to 5-V Input and 2.5-V Output With Optimized Ripple and Transient Response The compensation for each solution was optimized to work over the full input range. Many applications have a fixed input voltage rail. It is possible to modify the compensation to obtain a faster transient response for a given input voltage operating point. U1 Optional VIN 1 2 Cin2 + VOUT VIN EN CO1 LMZ10503 Cin1 Ccomp FB 5 CO3 CO2 Rfbt GND 4, EP SS 3 VOUT 6, 7 Rcomp CSS Optional Rfbb Figure 26. Optimized Schematic for 2.5-V Output Based on 3.3-V to 5-V Input Table 5. Bill of Materials, VIN = 3.3 V to 5 V, VOUT = 2.5 V, IOUT (MAX) = 3 A, Optimized for Low Input and Output Ripple Voltage and Fast Transient Response DESIGNATOR DESCRIPTION CASE SIZE MANUFACTURER MANUFACTURER P/N QTY. U1 SIMPLE SWITCHER PFM-7 Texas Instruments LMZ10503 1 Cin1 22 F, X5R, 10 V 1210 AVX 1210ZD226MAT 2 Cin2 (1) 220 F, 10 V, ALElec E Panasonic EEE1AA221AP 1 (1) 4.7 F, X5R, 10 V 0805 AVX 0805ZD475MAT 1 CO2 (1) 22 F, X5R, 6.3 V 1206 AVX 12066D226MAT 1 CO3 100 F, X5R, 6.3 V 1812 AVX 18126D107MAT 1 Rfbt 75 k 0402 Vishay Dale CRCW040275K0FKED 1 Rfbb 34.8 k 0402 Vishay Dale CRCW040234K8FKED 1 Rcomp 1 k 0402 Vishay Dale CRCW04021K00FKED 1 Ccomp 220 pF, 5%, C0G, 50 V 0402 Murata GRM1555C1H221JA01D 1 CSS 10 nF, 10%, X7R, 16 V 0402 Murata GRM155R71C103KA01 1 CO1 (1) Optional components, include for low input and output voltage ripple. Table 6. Output Voltage Setting (Rfbt = 75 k) 20 VOUT Rfbb 3.3V 23.7 k 2.5 V 34.8 k 1.8 V 59 k 1.5 V 84.5 k 1.2 V 150 k 0.9 V 590 k Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 8.3.2 Application Schematic for 3.3-V to 5-V Input and 2.5-V Output The compensation for each solution was optimized to work over the full input range. Many applications have a fixed input voltage rail. It is possible to modify the compensation to obtain a faster transient response for a given input voltage operating point. U1 VIN 1 VOUT VIN + Cin4 Cin3 Cin2 Cin1 CO1 LMZ10503 Ren1 Cin5 VOUT 6, 7 2 FB EN SS 3 CO2 CO3 5 GND 4, EP Rfbt CSS Rcomp Ccomp Rfbb Figure 27. Schematic for 2.5-V Output Based on 3.3-V to 5-V Input Table 7. Bill of Materials for Evaluation Board, VIN = 3.3 V to 5 V, VOUT = 2.5 V, IOUT (MAX) = 3 A DESIGNATOR DESCRIPTION CASE SIZE MANUFACTURER MANUFACTURER P/N QUANTITY U1 SIMPLE SWITCHER PFM-7 Texas Instruments LMZ10503 1 Cin1 1 F, X7R, 16 V 0805 TDK C2012X7R1C105K 1 Cin2, CO1 4.7 F, X5R, 6.3 V 0805 TDK C2012X5R0J475K 2 Cin3, CO2 22 F, X5R, 16 V 1210 TDK C3225X5R1C226M 2 Cin4 47 F, X5R, 6.3 V 1210 TDK C3225X5R0J476M 1 Cin5 220 F, 10 V, AL-Elec E Panasonic EEE1AA221AP 1 CO3 100 F, X5R, 6.3 V 1812 TDK C4532X5R0J107M 1 Rfbt 75 k 0805 Vishay Dale CRCW080575K0FKEA 1 Rfbb 34.8 k 0805 Vishay Dale CRCW080534K8FKEA 1 Rcomp 1.1 k 0805 Vishay Dale CRCW08051K10FKEA 1 Ccomp 180 pF, 5%, C0G, 50 V 0603 TDK C1608C0G1H181J 1 Ren1 100 k 0805 Vishay Dale CRCW0805100KFKEA 1 CSS 10 nF, 5%, C0G, 50 V 0805 TDK C2012C0G1H103J 1 Table 8. Output Voltage Setting (Rfbt = 75 k) VOUT Rfbb 3.3V 23.7 k 2.5 V 34.8 k 1.8 V 59 k 1.5 V 84.5 k 1.2 V 150 k 0.9 V 590 k Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 21 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 8.3.3 EMI Tested Schematic for 2.5-V Output Based on 3.3-V to 5-V Input The compensation for each solution was optimized to work over the full input range. Many applications have a fixed input voltage rail. It is possible to modify the compensation to obtain a faster transient response for a given input voltage operating point. U1 VIN 1 VOUT VIN VOUT 6, 7 CO1 LMZ10503 Cin3 Cin2 Cin1 2 FB EN SS 3 5 GND 4, EP Rfbt CSS Rcomp Ccomp Rfbb Figure 28. EMI Tested Schematic for 2.5-V Output Based on 3.3-V to 5-V Input Table 9. Bill of Materials, VIN = 5 V, VOUT = 2.5 V, IOUT (MAX) = 3 A, Tested With EN55022 Class B Radiated Emissions DESIGNATOR DESCRIPTION CASE SIZE MANUFACTURER MANUFACTURER P/N QUANTITY U1 SIMPLE SWITCHER PFM-7 Texas Instruments LMZ10503 1 Cin1 1 F, X7R, 16 V 0805 TDK C2012X7R1C105K 1 Cin2 4.7 F, X5R, 6.3 V 0805 TDK C2012X5R0J475K 1 Cin3 47 F, X5R, 6.3 V 1210 TDK C3225X5R0J476M 1 CO1 100 F, X5R, 6.3 V 1812 TDK C4532X5R0J107M 1 Rfbt 75 k 0805 Vishay Dale CRCW080575K0FKEA 1 Rfbb 34.8 k 0805 Vishay Dale CRCW080534K8FKEA 1 Rcomp 1.1 k 0805 Vishay Dale CRCW08051K10FKEA 1 Ccomp 180 pF, 5%, C0G, 50 V 0603 TDK C1608C0G1H181J 1 CSS 10 nF, 5%, C0G, 50 V 0805 TDK C2012C0G1H103J 1 Table 10. Output Voltage Setting (Rfbt = 75 k) 22 VOUT Rfbb 3.3 V 23.7 k 2.5 V 34.8 k 1.8 V 59 k 1.5 V 84.5 k 1.2 V 150 k 0.9 V 590 k Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 9 Power Supply Recommendations The LMZ10503 device is designed to operate from an input voltage supply range between 2.95 V and 5.5 V. This input supply should be well regulated and able to withstand maximum input current and maintain a stable voltage. The resistance of the input supply rail should be low enough that an input current transient does not cause a high enough drop at the LMZ10503 supply voltage that can cause a false UVLO fault triggering and system reset. If the input supply is more than a few inches from the LMZ10503, additional bulk capacitance may be required in addition to the ceramic bypass capacitors. The amount of bulk capacitance is not critical, but a 47F or 100-F electrolytic capacitor is a typical choice. 10 Layout 10.1 Layout Guidelines The PCB copper heat sink must be connected to the exposed pad (EP). Approximately thirty six, 8 mil thermal vias spaced 59 mils (1.5 mm) apart must connect the top copper to the bottom copper. For an extended discussion and formulations of thermal rules of thumb, refer to AN-2020 Thermal Design By Insight, Not Hindsight (SNVA419). For an example of a high thermal performance PCB layout with RJA of 20C/W, refer to the evaluation board application note AN-2022 LMZ1050x Evaluation Board (SNVA421) and for results of a study of the effects of the PCB designs, refer to AN-2026 Effect of PCB Design on Thermal Performance of SIMPLE SWITCHER Power Modules (SNVA424). PCB layout is an important part of DC-DC converter design. Poor board layout can disrupt the performance of a DC-DC converter and surrounding circuitry by contributing to EMI, ground bounce and resistive voltage drop in the traces. These can send erroneous signals to the DC-DC converter resulting in poor regulation or instability. Good layout can be implemented by following a few simple design rules. 1. Minimize area of switched current loops. From an EMI reduction standpoint, it is imperative to minimize the high di/dt current paths. The high current that does not overlap contains high di/dt, see Figure 29. Therefore physically place input capacitor (Cin1) as close as possible to the LMZ10503 VIN pin and GND exposed pad to avoid observable high-frequency noise on the output pin. This will minimize the high di/dt area and reduce radiated EMI. Additionally, grounding for both the input and output capacitor should consist of a localized top side plane that connects to the GND exposed pad (EP). 2. Have a single point ground. The ground connections for the feedback, soft-start, and enable components should be routed only to the GND pin of the device. This prevents any switched or load currents from flowing in the analog ground traces. If not properly placed, poor grounding can result in degraded load regulation or erratic output voltage ripple behavior. Provide the single point ground connection from pin 4 to EP. 3. Minimize trace length to the FB pin. Both feedback resistors, Rfbt and Rfbb, and the compensation components, Rcomp and Ccomp, should be located close to the FB pin. Since the FB node is high impedance, keep the copper area as small as possible. This is most important as relatively high value resistors are used to set the output voltage. 4. Make input and output bus connections as wide as possible. This reduces any voltage drops on the input or output of the converter and maximizes efficiency. To optimize voltage accuracy at the load, ensure that a separate feedback voltage sense trace is made at the load. Doing so will correct for voltage drops and provide optimum output accuracy. 5. Provide adequate device heat-sinking. Use an array of heat-sinking vias to connect the exposed pad to the ground plane on the bottom PCB layer. If the PCB has multiple copper layers, thermal vias can also be employed to make connection to inner layer heat-spreading ground planes. For best results use a 6 x 6 via array with minimum via diameter of 8 mils thermal vias spaced 59 mils (1.5 mm). Ensure enough copper area is used for heat-sinking to keep the junction temperature below 125C. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 23 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 10.2 Layout Examples Figure 29. Critical Current Loops to Minimize Top View Thermal Vias GND GND EXPOSED PAD 6 7 VOUT VOUT VIN 1 2 3 4 5 FB GND SS EN CIN VIN RENT CSS RENB COUT VOUT RFBT CFF RFBB GND Plane Figure 30. PCB Layout Guide Figure 31. Top Copper 24 Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 Layout Examples (continued) Figure 32. Internal Layer 1 (Ground) Figure 33. Internal Layer 2 (Ground and Signal Traces) Figure 34. Bottom Copper Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 25 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 10.3 Estimate Power Dissipation and Thermal Considerations Use the current derating curves in the Typical Characteristics section to obtain an estimate of power loss (PIC_LOSS). For the design case of VIN = 5 V, VOUT = 2.5 V, IOUT = 3 A, TA(MAX) = 85C , and TJ(MAX) = 125C, the device must see a thermal resistance from case to ambient (CA) of less than: TJ(MAX) TA(MAX) TCA t TJC PIC_LOSS (21) TCA o 125o C 85o C C 1.9 0.56 W W o 69.5 C W (22) Given the typical thermal resistance from junction to case (JC) to be 1.9C/W (typical). Continuously operating at a TJ greater than 125C will have a shorten life span. To reach CA = 69.5C/W, the PCB is required to dissipate heat effectively. With no airflow and no external heat, a good estimate of the required board area covered by 1-oz. copper on both the top and bottom metal layers is: Board Area_cm 2 t Board Area_cm 2 t 500 o Cu cm 2 u T CA W 500 o 69.5 C W o u Cu cm W (23) 2 (24) As a result, approximately 7.2 square cm of 1-oz. copper on top and bottom layers is required for the PCB design. 26 Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 10.4 Power Module SMT Guidelines The recommendations below are for a standard module surface mount assembly * Land Pattern - Follow the PCB land pattern with either soldermask defined or non-soldermask defined pads * Stencil Aperture - For the exposed die attach pad (DAP), adjust the stencil for approximately 80% coverage of the PCB land pattern - For all other I/O pads use a 1:1 ratio between the aperture and the land pattern recommendation * Solder Paste - Use a standard SAC Alloy such as SAC 305, type 3 or higher * Stencil Thickness - 0.125 to 0.15 mm * Reflow - Refer to solder paste supplier recommendation and optimized per board size and density * Maximum number of reflows allowed is one * Refer to Design Summary LMZ1xxx and LMZ2xxx Power Modules Family (SNAA214) for reflow information. Figure 35. Sample Reflow Profile Table 11. Sample Reflow Profile Table PROBE MAX TEMP (C) REACHED MAX TEMP TIME ABOVE 235C REACHED 235C TIME ABOVE 245C REACHED 245C TIME ABOVE 260C REACHED 260C 1 242.5 6.58 0.49 6.39 2 242.5 7.10 0.55 6.31 0.00 - 0.00 - 0.00 7.10 0.00 3 241.0 7.09 0.42 6.44 - 0.00 - 0.00 - Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 27 LMZ10503 SNVS641K - JANUARY 2010 - REVISED MAY 2017 www.ti.com 11 Device and Documentation Support 11.1 Device Support 11.1.1 Third-Party Products Disclaimer TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE. 11.1.2 Development Support 11.1.2.1 Custom Design With WEBENCH(R) Tools Click here to create a custom design using the LMZ10503 device with the WEBENCH(R) Power Designer. 1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements. 2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. Compare the generated design with other possible solutions from Texas Instruments. The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability. In most cases, these actions are available: * Run electrical simulations to see important waveforms and circuit performance * Run thermal simulations to understand board thermal performance * Export customized schematic and layout into popular CAD formats * Print PDF reports for the design, and share the design with colleagues Get more information about WEBENCH tools at www.ti.com/WEBENCH. 11.2 Documentation Support 11.2.1 Related Documentation For related documentation, see the following: * AN-2027 Inverting Application for the LMZ14203 SIMPLE SWITCHER Power Module (SNVA425) * Absolute Maximum Ratings for Soldering (SNOA549) * AN-2022 LMZ1050x Evaluation Board (SNVA421) * AN-2024 LMZ1420x / LMZ1200x Evaluation Board (SNVA422) * AN-2013 LMZ1050x/LMZ1050xEXT SIMPLE SWITCHER Power Module (SNVA417) * AN-2020 Thermal Design By Insight, Not Hindsight (SNVA419) * AN-2026 Effect of PCB Design on Thermal Performance of SIMPLE SWITCHER Power Modules (SNVA424) * Design Summary LMZ1xxx and LMZ2xxx Power Modules Family (SNAA214) 11.3 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 11.4 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2ETM Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. 28 Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 LMZ10503 www.ti.com SNVS641K - JANUARY 2010 - REVISED MAY 2017 Community Resources (continued) Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 11.5 Trademarks E2E is a trademark of Texas Instruments. SIMPLE SWITCHER, WEBENCH are registered trademarks of Texas Instruments. All other trademarks are the property of their respective owners. 11.6 Electrostatic Discharge Caution 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. 11.7 Glossary SLYZ022 -- TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Submit Documentation Feedback Copyright (c) 2010-2017, Texas Instruments Incorporated Product Folder Links: LMZ10503 29 PACKAGE OPTION ADDENDUM www.ti.com 27-Apr-2017 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) LMZ10503TZ-ADJ/NOPB ACTIVE TO-PMOD NDW 7 250 RoHS (In Work) & Green (In Work) CU SN Level-3-245C-168 HR -40 to 125 LMZ10503 TZ-ADJ LMZ10503TZE-ADJ/NOPB ACTIVE TO-PMOD NDW 7 45 RoHS (In Work) & Green (In Work) CU SN Level-3-245C-168 HR -40 to 125 LMZ10503 TZ-ADJ LMZ10503TZX-ADJ/NOPB ACTIVE TO-PMOD NDW 7 500 RoHS (In Work) & Green (In Work) CU SN Level-3-245C-168 HR -40 to 125 LMZ10503 TZ-ADJ (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) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (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. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 27-Apr-2017 continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 27-May-2018 TAPE AND REEL INFORMATION *All dimensions are nominal Device LMZ10503TZ-ADJ/NOPB LMZ10503TZX-ADJ/NOP B 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 TOPMOD NDW 7 250 330.0 24.4 10.6 14.22 5.0 16.0 24.0 Q2 TOPMOD NDW 7 500 330.0 24.4 10.6 14.22 5.0 16.0 24.0 Q2 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 27-May-2018 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMZ10503TZ-ADJ/NOPB TO-PMOD NDW 7 250 367.0 367.0 45.0 LMZ10503TZX-ADJ/NOPB TO-PMOD NDW 7 500 367.0 367.0 45.0 Pack Materials-Page 2 MECHANICAL DATA NDW0007A BOTTOM SIDE OF PACKAGE TOP SIDE OF PACKAGE TZA07A (Rev D) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated (TI) reserves 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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