BU90002GWZEVK-101 ROHM

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 ROHMs 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 ROHMs 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 Limit Parameter Symbol Unit Conditions MIN TYP MAX Supply Voltage BU90002GWZ V 4.0 - 5.5 V CC Output Voltage / Current V - 3.300 - V OUT BU90002GWZ IOUT - - 1 A Evaluation Board Below is evaluation board with the BU90002GWZ. EN Vout GND BD9673EFJ Eval Board Fig 1: BU90002GWZ Evaluation Board 1 Applic ation 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 (V , EN and MODE) and the output (V ). IN OUT Fig 3: BU90002GWZ Evaluation Board I/O Evaluation Board Operation Procedures Below is the procedure to operate the evaluation board. 1. Connect power supplys GND terminal to GND test point TP2 on the evaluation board. 2. Connect power supplys V terminal to V test point TP1 on the evaluation board. This will provide V to the IC U1. Please CC IN IN note that the V should be in range of 4.0V to 5.5V. CC 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 V (+3.3V) can be measured at the test point TP3. Now turn on the load. The load OUT 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: I vs. V when OCP active OUT OUT Page 2 of 7