LMR62421XSDDEMO/NOPB

User's Guide SNVA507A – November 2011 – Revised April 2013 AN-2197 LMR62421 Demo Board 1 Introduction The Texas Instruments LMR62421 is a high frequency switching boost regulator which offers small size and high power conversion efficiency. The part operates at a 1.6MHz switching frequency. It provides all the active functions to provide local DC/DC conversion with fast-transient response and accurate regulation in the smallest PCB area capable of supplying up to 2.1A of switch current. The LMR62421 is internally compensated, so it is simple to use, and requires few external components. The LMR62421 uses current-mode control to regulate the output voltage in a range from 3V to 24V. Additional features include internal soft start which helps reduce inrush current and thermal shutdown. This application note describes the demo board supplied to demonstrate the operation of this part and give information on its usage. Top View Bottom View Figure 1. LMR62421 Demo Board All trademarks are the property of their respective owners. SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated AN-2197 LMR62421 Demo Board 1 Features 2 Features • • • • • • • 3 www.ti.com 2.7V to 5.5V Input Voltage Range 12V Output Voltage (default setting) 500mA Output Current from 3.5V input supply 300mA Output Current from 2.7V input supply Switching Frequency of 1.6 MHz Low Component Count PCB size: 27.5mm × 36.9mm Shutdown Operation The demo board includes a pull-up resistor R3 to enable the device once VIN has exceeded 1.8V. Use the EN post to disable the device by pulling this node to GND. A logic signal may be applied to the post to test startup and shutdown of the device. 4 Adjusting the Output Voltage The output voltage can be changed from 12V to another voltage by adjusting the feedback resistors using the following equation: VOUT = VFB(1 + (R1/R2)) (1) Where VFB is 1.255V. 5 Feedforward Compensation The feedforward capacitor CF should be selected to set the compensation zero at approximately 8 kHz. The value of CF is calculated using: CF = 1 / (2 × π × 8k × R1) (2) The value of CF is calculated after R1 is selected for the output voltage needed for the specific application. For more information on component selection and features, see LMR62421 SIMPLE SWITCHER 24Vout, 2.1A Step-Up Voltage Regulator in SOT-23 (SNVS734). 2 AN-2197 LMR62421 Demo Board SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated LMR62421 Demo Board Schematic www.ti.com 6 LMR62421 Demo Board Schematic L1 U1 VIN 2 VIN REN SW CF LMR62421 EN 3 CIN 4 EN VOUT D1 6 RFBT FB COUT COUT2 CHF (opt) 5 AGND PGND 1 RFBB GND GND Figure 2. LMR62421 Demo Board Schematic Table 1. Bill of Materials LMR62421 ID Part Number Type Size U1 LMR62421 1.6MHz - SpaceEfficient Boost 6-pin WSON L1 7447779006 Inductor D1 B220A-13-F Diode Cin GRM21BR71A106KE51L Cout GRM31CR71E106KA12L Cout2 optional CF C0603C221J5GACTU CHF Rfbt Parameters Vendor Texas Instruments Shielded Inductor, 6.8µH, 2.91A Wurth SMA Schottky, 20V, 2A Diodes Inc. Capacitor 0805 Ceramic, 10µF, 10V, X7R Murata Capacitor 1206 Ceramic, 10µF, 25V, X7R Murata 1206 additional output cap Capacitor 0603 Ceramic, 220pF, 50V, C0G/NP0 Kemet GRM188R71H223KA01D Capacitor 0603 Ceramic, 0.022uF, 50V, X7R Murata CRCW060386K6FKEA Resistor 0603 86.6 kΩ Vishay Rfbb CRCW060310K2FKEA Resistor 0603 10.2 kΩ Vishay Ren CRCW06031M00JNEA Resistor 0603 1.0 MegΩ Vishay EN 5014 Test Point Loop Yellow Keystone VIN 5010 Test Point Loop Red Keystone VOUT 5013 Test Point Loop Orange Keystone GND 5011 Test Point Loop Black Keystone SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated AN-2197 LMR62421 Demo Board 3 Quick Setup Procedures 7 www.ti.com Quick Setup Procedures Step 1: Connect a power supply to VIN terminals. VIN range: 2.7V to 5.5V Step 2: Connect a load to VOUT terminals. IOUT range: 0mA to 500mA Step 3: Do not allow the EN pin to float or be greater than VIN + 0.3V. EN pin must be connected to VIN by means R3 for normal operation. Short this to ground to shutdown the part. Step 4: Turn on VIN with 0A load applied, check VOUT with a voltmeter. Nominal 12V Step 5: Apply a 500mA load and check VOUT. Nominal 12V Measurements Ammeter A Ammeter A + VOUT GND GND + - Electronic Load - 8 Power Supply VIN Voltmeter V V Voltmeter Evaluation Board Figure 3. Efficiency Measurements Oscilloscope VOUT GND Chf Figure 4. Voltage Ripple Measurements 4 AN-2197 LMR62421 Demo Board SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated Measurements www.ti.com I I I I I GND VOUT 5 6 A B C D E F SPARE 4 VOUT SENSE+ 3 VOUT SENSE - 2 VIN SENSE - 1 VIN SENSE+ EN VIN I I I I I I I Figure 5. Edge Connector Schematic SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated AN-2197 LMR62421 Demo Board 5 Typical Performance Characteristics 9 www.ti.com Typical Performance Characteristics Efficiency vs. Load Current LMR62421, VOUT = 12V Load regulation, VOUT = 12V 100 0.100 95 0.075 0.050 85 ERROR [%] EFFICIENCY [%] 90 80 75 70 65 60 0.025 0.000 -0.025 Vin = 2.7V Vin = 3.5V Vin = 5.5V -0.050 55 -0.075 50 -0.100 0.0 0.1 0.2 0.3 IOUT[A] 0.4 0.5 Output Voltage Ripple and Switching Waveform, VIN = 2.7, VOUT = 12V, IOUT = 300mA VOUT ripple 100 mV/Div 0.0 0.1 0.2 0.3 IOUT[A] 0.4 Output Ripple and Switching Waveform, VIN = 3.5, VOUT = 12V, IOUT = 500mA VOUT ripple VSW 5V/Div 100 mV/Div VSW 5V/Div TIME (200 ns/DIV) TIME (200 ns/DIV) Load Transient VIN = 5.5, VOUT = 12V, IOUT = 50mA to 500mA Start Up with Enable VIN = 3.5, VOUT = 12V, IOUT = 500mA VOUT ripple 0.5 EN 2V/Div 1V/Div VSW 2V/Div IOUT 100 mA/Div IOUT 200 mA/Div TIME (1 ms/DIV) TIME (200 µs/DIV) 6 AN-2197 LMR62421 Demo Board SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated Layout www.ti.com 10 Layout Figure 6. Top Layer Figure 7. Top Overlay SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated AN-2197 LMR62421 Demo Board 7 Layout www.ti.com Figure 8. Bottom Layer Figure 9. Bottom Overlay 8 AN-2197 LMR62421 Demo Board SNVA507A – November 2011 – Revised April 2013 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated 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. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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