LMR61428XMMEVM/NOPB

User's Guide SNVU193A – October 2012 – Revised April 2013 AN-2281 LMR61428 Evaluation Module 1 Introduction The LMR61428 evaluation module is designed to provide the power supply design engineer with a fully functional regulator design. The evaluation module takes the input from a single Li-Ion battery and boosts the voltage up to 5V at a constant load capability of 500mA. The switching frequency of the boost regulator is set to about 1200 kHz which helps in reducing the solution size and keeping switching noise out of the AM radio band. The printed circuit board consists of 4 layers of copper on FR4 material. The first middle layer is a solid ground layer which helps in minimizing the AC current loop. This user's guide contains the evaluation module schematic, a quick setup procedure using a bench power supply, and a Bill-of-Materials (BOM). For complete circuit design information, see LMR61428 SIMPLE SWITCHER 14Vout, 2.85A Step-Up Voltage Regulator in VSSOP (SNVS815). 2 Features • • • • 3 One cell Li-Ion battery for Input Voltage 5V Output Voltage at 500mA Output Current Switching Frequency of 1.2 MHz Small Solution Size: 2.287 × 1.058 inches (58.09 × 26.87 mm) Evaluation Board Schematic L1 1 Cell Li-ion VIN SW 5V at 0.5A VOUT D1 30203001 U1 J1 + VOUT 3 2 1 7 BOOT Rfbt SW Cff 8 LMR61428 Rdd Ren EN 2 6 Cboot Rt 3 Cdd + 4 EN Cin VDD FB PGND FREQ SGND Co1 Co2 1 GND 5 Rfbb GND Figure 1. LMR61428 Evaluation Module Schematic All trademarks are the property of their respective owners. SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback AN-2281 LMR61428 Evaluation Module Copyright © 2012–2013, Texas Instruments Incorporated 1 Powering and Loading Considerations 4 www.ti.com Powering and Loading Considerations Read this entire section prior to attempting to power the evaluation board. 4.1 Quick Start Procedure Step 1: Set the bench power supply current limit to 3A. Set the power supply voltage to 3.5V. Turn off the power supply output. Connect the power supply to the LMR61428 demo board. Positive connection to VIN and negative connection to GND. Step 2: Connect a load, as high as 0.5A, to the VOUT terminal. Positive connection to VOUT and negative connection to GND. Step 3: Connect the shunt so as to short the pins 1 and 2 of the jumper J1. This sets the bootstrap to VOUT Step 4: The EN pin should be left open for normal operation. Step 5: Turn on the bench power supply with no load applied to the LMR61428. If the shunt for the jumper J1 was in place, the VOUT would be in regulation at a nominal 5V. Step 6: Gradually increase the load and VOUT should remain in regulation as the load is increased up to 0.5 Amps. 4.2 Shutdown Operation The EVM includes a pull-up resistor Ren to enable the device. Use the EN post to disable the device by pulling this node to GND. 4.3 Bootstrap Operation The EVM has a jumper installed to select the bootstrap option. The default condition is that the jumper be set such that the bootstrap voltage is obtained from the output. For more information, see LMR61428 SIMPLE SWITCHER 14Vout, 2.85A Step-Up Voltage Regulator in VSSOP (SNVS815). 4.4 Setting the Output Voltage The output voltage of the step-up regulator can be set between 1.24V and 14V. But because of the gated oscillator scheme, the maximum possible input to output boost ratio is fixed. For a boost regulator, VOUT / VIN = 1 / [1 − D] (1) The LMR61428 has a fixed duty cycle, D, of 70% typical. Therefore, VOUT / VIN = 1 / 0.3 (2) This sets the maximum possible boost ratio of VIN to VOUT to about 3 times. The user can now estimate what the minimum design inputs should be in order to achieve a desired output, or what the output would be when a certain minimum input is applied. For example, if the desired VOUT was 14V, then the least VIN should be higher than VOUT / 3. If the input voltage fell below this threshold, the output voltage would not be regulated because of the fixed duty cycle. If the minimum VIN was guaranteed at 2V, the max possible VOUT would be VIN × 3. The VOUT is set by connecting a feedback resistive divider made of Rfbt and Rfbb. The feedback resistor values are selected as follows: Rfbb = Rfbt /[(VOUT/ 1.24) −1] (3) A value of 150kΩ is suggested for Rfbt. Then, Rfbb can be selected using Equation 3. A 39pF capacitor (Cff) connected across Rfbt helps in feeding back most of the AC ripple at VOUT to the FB pin. This helps reduce the peak-to-peak output voltage ripple as well as improve the efficiency of the step-up regulator, because a set hysteresis of 30mV at the FB pin is used for the gated oscillator control scheme. 2 AN-2281 LMR61428 Evaluation Module SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated Powering and Loading Considerations www.ti.com Typical Test Setup Ammeter A Ammeter A + VOUT GND GND Voltmeter V Power Supply + - Electronic Load - 4.5 VIN V Voltmeter Demo Board Figure 2. Efficiency Measurements Oscilloscope VOUT GND Chf Figure 3. Voltage Ripple Measurements SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback AN-2281 LMR61428 Evaluation Module Copyright © 2012–2013, Texas Instruments Incorporated 3 Powering and Loading Considerations www.ti.com I I I I I GND VOUT 5 6 A B C D E F GND 4 VOUT SENSE+ 3 VOUT SENSE - 2 SPARE 1 VIN SENSE+ EN VIN I I I I I I I Figure 4. Edge Connector Schematic 4 AN-2281 LMR61428 Evaluation Module SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated Powering and Loading Considerations www.ti.com 4.6 Board Images Figure 5. Top Side SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback AN-2281 LMR61428 Evaluation Module Copyright © 2012–2013, Texas Instruments Incorporated 5 Powering and Loading Considerations www.ti.com Figure 6. Bottom Side 6 AN-2281 LMR61428 Evaluation Module SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated Typical Performance Characteristics www.ti.com 5 Typical Performance Characteristics Efficiency vs. Load Current VOUT = 5V Load Transient Waveforms VIN = 3.6V, IOUT = 50 to 500mA 84 IOUT 82 EFFICIENCY (%) 80 100 mA/Div 78 76 VOUT = 5V 74 Vin = 3.0V Vin = 3.1V Vin = 3.2V Vin = 3.4V Vin = 3.5V Vin = 3.6V Vin = 3.8V Vin = 4.0V 72 70 68 66 64 50 mV/Div 100 Ps/DIV 0.000.060.120.180.240.300.360.420.480.54 IOUT(A) Switching Node and Output Voltage Waveforms VIN = 3.6V, IOUT = 500mA Startup Waveform VSW VOUT = 5V 5V/Div 2V/Div IOUT = 0.5A 0.5A/Div VOUT = 5V VIN = 3V 1V/Div 50 mV/Div 10 Ps/DIV 500 Ps/DIV SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback AN-2281 LMR61428 Evaluation Module Copyright © 2012–2013, Texas Instruments Incorporated 7 Bill of Materials 6 8 www.ti.com Bill of Materials ID Part Number Type Size U1 LMR61428 Boost Regulator SOT-23 L1 SRU1048-8R2Y Inductor SMD Parameters Qty Vendor 1 Texas Instruments 8.2uH, 4.6A, 0.015 ohm, 1 Bourns D1 B220A-13-F Diode SMA Schottky, 20V, 2A 1 Toshiba Cin 293D226X9010C2TE3 Capacitor SMD Tantalum, 22uF, 10V 1 VishaySprague Co1 594D686X0010C2T Capacitor SMD Tantalum, 68uF, 10V 1 VishaySprague Co2 08053D105KAT2A Capacitor 0805 Ceramic, 1uF, 25V, X5R 1 AVX Cdd C0603C105K4PACTU Capacitor 0603 Ceramic, 1uF, 16V, X5R 1 Kemet Cff GRM1885C2A390JA01D Capacitor 0603 Ceramic, 39pF, 100V, C0G/NP0 1 MuRata Rfbt RG1608P-154-B-T5 Resistor 0603 150 kΩ 1 Susumu Co Ltd Rfbb RG1608P-4992-B-T5 Resistor 0603 49.9 kΩ 1 Susumu Co Ltd Rt CRCW0603118KFKEA Resistor 0603 118 kΩ 1 Vishay-Dale Rdd CRCW060349R9FKEA Resistor 0603 49.9 Ω 1 Vishay-Dale Ren CRCW060310K0FKEA Resistor 0603 10.0 kΩ 1 Vishay-Dale EN 5014 Test Point Loop Yellow 1 Keystone VIN 5010 Test Point Loop Red 1 Keystone VOUT 5013 Test Point Loop Orange 1 Keystone GND 5011 Test Point Loop Black 2 Keystone SW 5012 Test Point Loop White 1 Keystone J1 PBC03SAAN Header 100mil, 1x3 1 Sullins Connector Solutions SH-J1 969102-0000-DA Shunt 100mil, Black 1 3M AN-2281 LMR61428 Evaluation Module SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated PCB Layout www.ti.com 7 PCB Layout Figure 7. Top Copper Figure 8. Top Overlay SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback AN-2281 LMR61428 Evaluation Module Copyright © 2012–2013, Texas Instruments Incorporated 9 PCB Layout www.ti.com Figure 9. Internal Layer 1 Figure 10. Internal Layer 2 10 AN-2281 LMR61428 Evaluation Module SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated PCB Layout www.ti.com Figure 11. Bottom Copper Figure 12. Bottom Overlay SNVU193A – October 2012 – Revised April 2013 Submit Documentation Feedback AN-2281 LMR61428 Evaluation Module Copyright © 2012–2013, Texas Instruments Incorporated 11 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve 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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