BU90002GWZ-EVK-101

ROHM Switching Regulator Solutions Evaluation Board: Synchronous Buck Converter Integrated FET No.000000000 BU90002GWZEVK-101 (3.3V | 1A Output)     Introduction This application note will provide the steps necessary to operate and evaluate ROHM’s synchronous buck DC/DC converter using the BU90002GWZ evaluation boards. Component selection, board layout recommendations, operation procedures and application data is provided. Description This evaluation board has been developed for ROHM’s synchronous buck DC/DC converter customers evaluating BU90002GWZ. While accepting a power supply of 4.0-5.5V, an output of 3.3V can be produced. The IC has internal 250mOhm high-side P-channel MOSFET and 220mOhm low-side N-channel MOSFET and a synchronization frequency range of 5.4MHz to 6.6MHz. A fixed Soft Start circuit prevents in-rush current during startup along with UVLO (low voltage error prevention circuit) and TSD (thermal shutdown detection) protection circuits. An EN pin allows for simple ON/OFF control of the IC to reduce standby current consumption. A MODE pin allows the user to select Forced PWM (Pulse Width Modulation) mode or PFM (Pulse Frequency Modulation) and PWM auto change mode utilized power save operation at light load current. Applications Smart phones, Cell phones, Portable applications and Micro DC/DC modules, USB accessories Evaluation Board Operating Limits and Absolute Maximum Ratings Parameter Symbol Limit Unit MIN TYP MAX VCC 4.0 - 5.5 V VOUT - 3.300 - V IOUT - - 1 A Conditions Supply Voltage BU90002GWZ Output Voltage / Current BU90002GWZ  Evaluation Board Below is evaluation board with the BU90002GWZ. Fig 1: BU90002GWZ Evaluation Board 1 Application Note  Evaluation Board Schematic Below is evaluation board schematic for BU90002GWZ. Fig 2: BU90002GWZ Evaluation Board Schematic  Evaluation Board I/O Below is reference application circuit that shows the inputs (VIN, EN and MODE) and the output (VOUT). Fig 3: BU90002GWZ Evaluation Board I/O  Evaluation Board Operation Procedures Below is the procedure to operate the evaluation board. 1. Connect power supply’s GND terminal to GND test point TP2 on the evaluation board. 2. Connect power supply’s VCC terminal to VIN test point TP1 on the evaluation board. This will provide VIN to the IC U1. Please note that the VCC should be in range of 4.0V to 5.5V. 3. Set operation mode of IC by set position of shunt jumper of J2 (If Pin2 connect to Pin1, MODE pin of IC U1 will be pulled high and IC U1 will operate in Forced PWM mode, else MODE pin of IC U1 will be pulled low and IC U1 will operate in Automatic PFM/PWM mode). 4. Check if shunt jumper of J1 is at position ON (Pin2 connect to Pin1, EN pin of IC U1 is pulled high). 5. Connect electronic load to TP3 and TP4. Do not turn on load (electronic load is off power). 6. Turn on power supply. The output voltage VOUT (+3.3V) can be measured at the test point TP3. Now turn on the load. The load can be increased up to 1A MAX. Notes: In some cases that the evaluation board is not operated following the above power up sequence, the output current spike can exceed the current limitation 1A with electronic load 1A setting as shown in fig.4. Then the integrated OCP (Over Current Protection) will be active to protect the IC and the output voltage is about 0.3V instead of 3.3V as expected. In order to get the IC out of OCP, turn off any output loads and power down the input voltage. Then, follow the operating procedure listed above for normal operation of this IC. Fig 4: IOUT vs. VOUT when OCP active Page 2 of 7 Application Note  Reference Application Data for BU90002GWZEVK-101 Following graphs show hot plugging test, quiescent current, efficiency, load response, output voltage ripple response of the BU90002GWZ evaluation board. Fig 5: Hot Plug-in Test with Zener Diode Fig 6: Circuit Current vs. Power supply o Voltage Characteristics (Temp=25 C, P4SMA6.8A, VIN=5V, VOUT=3.3V, IOUT=0.6A, Automatic PFM/PWM Mode Automatic PFM/PWM Mode) Fig 8: Load Response Characteristics (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=0A1A, Automatic PFM/PWM Mode) Fig 7: Electric Power Conversion Rate (VOUT=3.3V, Automatic PFM/PWM Mode) Fig 9: Load Response Characteristics (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=1A0A, Automatic PFM/PWM Mode) Fig 10: Output Voltage Ripple Response Characteristics Fig 11: Output Voltage Ripple Response Characteristics (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=0A, Automatic (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=1A, Automatic PFM/PWM Mode) PFM/PWM Mode) Page 3 of 7 Application Note Fig 12: Hot Plug-in Test with Zener Diode P4SMA6.8A, VIN=5V, VOUT=3.3V, IOUT=0.6A, Forced PWM Mode Fig 13: Circuit Current vs. Power supply Fig 14: Electric Power Conversion Rate o Voltage Characteristics (Temp=25 C, (VOUT=3.3V, Forced PWM Mode) Forced PWM Mode) Fig 15: Load Response Characteristics (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=0A1A, Forced PWM Mode) Fig 16: Load Response Characteristics (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=1A0A, Forced PWM Mode) Fig 17: Output Voltage Ripple Response Characteristics (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=0A, Forced PWM Mode) Fig 18: Output Voltage Ripple Response Characteristics (VIN=5V, VOUT=3.3V, L=1.0uH, COUT=4.7uF, IOUT=1A, Forced PWM Mode) Page 4 of 7 Application Note  Evaluation Board Layout Guidelines Below are the guidelines that have been followed and recommended for BU90002GWZ designs. Fig 19: BU90002GWZ PCB Layout ① ② ③ The input capacitor CIN should be connect as closely possible to VIN pin and GND pin. From the output voltage to the FB pin line should be as separate as possible. COUT and L should be connected as closely as possible. The connection of L to the LX pin should be as short as possible. Fig 20: BU90002GWZEVK Board PCB layout  Calculation of Application Circuit Components Selection of inductor (L) The inductance significantly depends on output ripple current. As shown by following equation, the ripple current decreases as the inductor and/or switching frequency increase. ∆𝐈𝐋 = (𝐕𝐈𝐍 −𝐕𝐎𝐔𝐓 )×𝐕𝐎𝐔𝐓 𝐋×𝐕𝐈𝐍 ×𝐟 f: switching frequency, L: inductance, ΔIL: inductor current ripple As a minimum requirement, the DC current rating of the inductor should be equal to the maximum load current plus half of the inductor current ripples as shown by the following equation. 𝐈𝐋𝐏𝐄𝐀𝐊 = 𝐈𝐎𝐔𝐓𝐌𝐀𝐗 + ∆𝐈𝐋 𝟐 Page 5 of 7 Application Note  Evaluation Board BOM Below is a table with the build of materials. Part numbers and supplier references are provided. Item Qty. Ref Description Manufacturer Part Number 1 2 3 4 2 1 2 1 C1,C2 D1 J1,J2 L1 CAP CER 4.7UF 6.3V 10% X5R 0603 DIODE TVS 400W 6.8V UNI 5% SMD CONN HEADER VERT .100 3POS 15AU INDUCTOR POWER 1.0UH 2.3A SMD GRM188R60J475KE19D P4SMA6.8A 87224-3 MLP2520K1R0ST0S1 5 2 TP1,TP3 TEST POINT PC MULTI PURPOSE RED 6 7 8 2 1 2 TP2,TP4 U1 TEST POINT PC MULTI PURPOSE BLK IC REG BUCK SYNC 3.3V 1A 6WLCSP Shunt jumper for header J1, J2 Murata Littelfuse TE Connectivity TDK Keystone Electronics Keystone Electronics ROHM TE Connectivity 5010 5011 BU90002GWZ-E2 881545-1 Page 6 of 7 Application Note Notes No copying or reproduction of this document, in part or in whole, is permitted without the consent of ROHM Co.,Ltd. The content specified herein is subject to change for improvement without notice. The content specified herein is for the purpose of introducing ROHM's products (hereinafter "Products"). If you wish to use any such Product, please be sure to refer to the specifications, which can be obtained from ROHM upon request. Examples of application circuits, circuit constants and any other information contained herein illustrate the standard usage and operations of the Products. The peripheral conditions must be taken into account when designing circuits for mass production. Great care was taken in ensuring the accuracy of the information specified in this document. However, should you incur any damage arising from any inaccuracy or misprint of such information, ROHM shall bear no responsibility for such damage. The technical information specified herein is intended only to show the typical functions of and examples of application circuits for the Products. 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