National Semiconductor Application Note 2085 Alan Martin March 27, 2011 Introduction Board Specifications The LMZ23605/03, LMZ22005/03 evaluation boards are designed to be an easy-to-use platform to evaluate the full capabilities of this family of SIMPLE SWITCHER® power modules. The PCB construction has excellent thermal performance and includes extra locations for optional components that may not be required in the end application. The LMZ23605/03 can accept an input voltage rail between 6V and 36V and the LMZ22005/03 can accept an input voltage rail between 6V and 20V. The devices can deliver an adjustable and highly accurate output voltage as low as 0.8V and as high as 6V. The control architecture is constant frequency PWM with emulated current mode sensing. The control loop operates well with low ESR output capacitors such as ceramics or specialty polymer. The precision enable input allows for programmable UVLO on the input supply or flexibility in sequencing. The external soft-start capacitor facilitates controlled output rise time at startup. The module family is a reliable and robust solution with cycle-by-cycle valley current limit to protect for over current or short-circuit faults. Additionally there is thermal shutdown protection, and they will start up into a pre-biased output. The free-running switching frequency is 812 kHz (typ) and a 650 kHz to 950 kHz synchronization range is supported. • • • • • • VIN = 6V to 36V (LMZ22005/03 limited to 20V) Enable UVLO = 5.7V VOUT = 3.3V IOUT = 0 to 5A (LMZ23603 and LMZ22003 limited to 3A) θJA = 12°C / W, θJC = 1.9°C/W PCB designed on four layers; Inner are 2 oz; Outer are 3 oz. • Measures 3.5 in. x 3.5 in. (8.9 cm x 8.9 cm) and is 62mil (.062”) thick of FR4 laminate material • Max ambient temp of 70°C at full 5A load (12 Vin) For additional circuit considerations refer to the Applications Section of the LMZ23605/03 or LMZ22005/03 data sheets. For negative output voltage connections follow the method shown in AN-2027. LMZ23605/03, LMZ22005/03 Evaluation Board LMZ23605/03, LMZ22005/03 Evaluation Board 30131601 FIGURE 1. Evaluation Board Simplified Schematic AN-2085 © 2011 National Semiconductor Corporation 301316 www.national.com LMZ23605 3.3Vout Efficiency @ 25°C Ambient LMZ23605 3.3Vout Dissipation @ 25°C Ambient 100 8 80 70 60 8 Vin 12 Vin 20 Vin 24 Vin 30 Vin 36 Vin 50 40 0 6 DISSIPATION (W) EFFICIENCY (%) 36 Vin 30 Vin 24 Vin 20 Vin 12 Vin 8 Vin 7 90 5 4 3 2 1 0 1 2 3 4 OUTPUT CURRENT (A) 5 0 1 2 3 4 OUTPUT CURRENT (A) 30131637 LMZ23605 3.3Vout Dissipation @ 85°C 100 8 90 80 70 9 Vin 12 Vin 20 Vin 24 Vin 30 Vin 36 Vin 50 40 0 1 2 3 4 OUTPUT CURRENT (A) 6 DISSIPATION (W) EFFICIENCY (%) 36 Vin 30 Vin 24 Vin 20 Vin 12 Vin 9 Vin 7 60 5 30131638 LMZ23605 3.3Vout Efficiency @ 85°C 5 4 3 2 1 0 5 0 1 2 3 4 OUTPUT CURRENT (A) 30131630 5 30131631 LMZ23605 Load and Line Regulation @ 25°C Ambient LMZ23605 Current Limit VOUT = 3.3V 1.002 8 7 1.001 6 CURRENT (A) OUTPUT VOLTAGE (V) AN-2085 Performance Characteristics 1.000 9 Vin 12 Vin 20 Vin 24 Vin 30 Vin 36 Vin 0.999 0.998 0 1 2 3 4 OUTPUT CURRENT (A) Output Current 5 4 3 2 Input Current 1 0 5 0 4 8 12 16 20 24 28 32 36 INPUT VOLTAGE (V) 30131636 30131639 www.national.com 2 AN-2085 Output Ripple VOUT = 3.3V IOUT = 5A, BW to 20 MHz Output Ripple VOUT = 3.3V IOUT = 5A, BW to 250 MHz 30131620 30131621 LMZ23605 Load Step Response VIN = 12V VOUT = 3.3V, 0.5A to 5A Step LMZ23603 Load Step Response VIN = 12V VOUT = 3.3V, 0.5A to 3A Step 30131618 30131619 LMZ23605 Start-up LMZ23605 Pre-biased startup 30131640 30131641 3 www.national.com AN-2085 J1 and J2 are for input and output noise measurement. To implement this feature, populate the 1uF blocking capacitors and the 49.9 ohm source resistors. Install Amphenol coax connectors type 112404 (Digikey #ACX1051).The added RC network forms a 2X scope probe when used in conjunction with an input termination of 50 ohms at the oscilloscope, providing 5 times more sensitivity than a conventional 10x probe. J3 is for connection to a frequency response analyzer such as A/P Instruments (Ridley) or Venable Industries products. Refer to the FRA operating manual for this connection. Note: Do not place any type of shorting jumper to these three posts as that will cause a malfunction. Inductor current can be monitored by connecting a loop of between module pin 7 (Vout) and the Co array. First cut the top side conducting etch between the two vias adjacent to pin 7, then install a 5” loop of 22 ga insulated wire in the two vias. Monitor the inductor sense loop with an AC/DC oscilloscope current probe. The Vin input plane has solder mask openings where an input LC network can be placed to accommodate improved differential mode and conducted EMI performance. Additional component mounting pads are available to experiment with alternative Cin and Cout combinations. See Figure 6 for corresponding schematic locations. Notes Solder turrets are located on the edge of the PCB assembly for evaluation hookup to bench test equipment. The Enable input turret is designed for direct connection to the VIN turret. There is a resistive divider implemented on the board that establishes the 5.5V precision UVLO level of the board. A common user change to this divider is to raise the value of RENT to increase the operating UVLO to that of the target application. Refer to the respective data sheet for calculation. Note that if in the end application the module pin 3 enable voltage does not exceed 5.5V at maximum Vin, then enable clamp zener D1 can be omitted. Each implementation of the evaluation board is preset to 3.3V output; with current rating and maximum input voltage rating dictated by the model of module installed. A common user change is to adjust the output voltage for different requirements. A table of suggested resistor pairs are listed in Figure 1 for quick reference. Locations are provide for testing the operation as a coincident turn-on tracking supply (slave). To implement this feature, remove CSS and install Rtkt and Rtkb. Calculations are suggested in the respective data sheets. A turret is also provided for applying a clock to synchronize the module switching frequency anywhere between 650 kHz and 950 kHz. Note that a sustained “logic one” on this input corresponds to “zero hertz” and will cause the module to stop switching. PCB View and layout diagrams Gerber and CAD files can be downloaded from the LMZ23605 /03, LMZ22005/03 respective product folders. 30131614 FIGURE 2. Top View of Assembly www.national.com 4 AN-2085 30131609 FIGURE 3. Top Layer 30131610 FIGURE 4. Internal Layer I (Ground) Heat Sinking Layer 5 www.national.com AN-2085 30131611 FIGURE 5. Internal Layer II (Ground and Routing) Heat Sinking Layer 30131612 FIGURE 6. Bottom Layer (Ground) Heat Sinking Layer www.national.com 6 AN-2085 30131613 FIGURE 7. LMZ2360x / LMZ2200x PCB CAD package schematic DNP = Component not populated 7 www.national.com AN-2085 TABLE 1. Bill of Materials, VIN = 6V to 36V, VOUT = 3.3V, IOUT (MAX) = 5A (3A) Note: The same BOM applies to all implementations Designator Description Case Size Manufacturer Manufacturer P/N Quantity U1 SIMPLE SWITCHER® TO-PMOD-7 National Semiconductor LMZ23605TZ or LMZ23603TZ or LMZ22005TZ or LMZ22003TZ 1 CIN1 CIN5 CO1 CO6 0.047 µF, X7R, 50V 1206 Yageo America CC1206KRX7R9BB473 4 CIN2 CIN3 10 µF, X5R, 50V 1210 Taiyo Yuden UMK325BJ106MM-T 2 CIN6 OPT 150 µF,Aluminum Electrolytic, 50V G Panasonic EEE-FK1H151P 1 CO2 OPT 100 µF, X5R, 6.3V 1210 TDK C3225X5R0J107M 1 CO5 220 µF, Specialty Polymer, 6.3V Panasonic EEF-UE0J221LR 1 CFF DNP CSS 0.47µF, X7R, 16V 0805 AVX 0805YC474KAT2A 1 D1 5.1V 200mW SOD-323 Diodes Inc. MMSZ5231BS-7-F 1 RENB 12.7 kΩ 0805 Panasonic ERJ-6ENF1272V 1 RENT 42.2 kΩ 0805 Panasonic ERJ-6ENF4222V 1 RENH 100 Ω 0805 Vishay-Dale CRCW0805100RFKEA 1 RFBT 3.32 kΩ 0805 Vishay-Dale CRCW08053K32FKEA 1 RFBB 1.07 kΩ 0805 Vishay-Dale CRCW08051K07FKEA 1 RFRA 23.7 Ω 0805 Vishay-Dale CRCW080523R7FKEA 1 RFF DNP RSN 1.50 kΩ 0805 Vishay-Dale CRCW08051K50FKEA 1 www.national.com 8 AN-2085 9 www.national.com LMZ23605/03, LMZ22005/03 Evaluation Board Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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