Datasheet Single-chip Type with Built-in FET Switching Regulator Series Step-down Switching regulators with Built-in Power MOSFET BU9002xNUX Series General Description Applications The BU9002xNUX are a high efficiency 1MHz POL, 1Cell Li-ion battery for portable applications , synchronous step-down switching regulator with low USB accessories current PFM mode. It provides up to 1.5A load current and an input voltage Package(s) W(Typ.) x D(Typ.) x H(Max.) range from 4.5V to 5.5V, optimized for various VSON008X2030 2.00mm x 3.00mm x 0.60mm applications with input voltage range up to 5V. BU9002xNUX has a mode control pin that 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. Features Fast transient response Automatic PFM/PWM operation. Forced PWM operation Internal Soft Start Under voltage lockout VSON008X2030 Over current protection Thermal shutdown Typical Application Circuit(s) Lineup Output Part No. voltage BU90023NUX 1.230V BU90028NUX 1.175V Figure 1. Typical Application Circuit(s) Pin Description(s) Pin Configuration(s) Pin No. Symbol Function (TOP VIEW) 1 LX Inductor connection pin 2 MODE Forced PWM mode pin LX FB 3 PVIN Power supply input pin MODE PGND 4 VIN Power supply input pin PVIN AGND 5 EN Enable pin VIN EN 6 AGND GND pin 7 PGND GND pin 8 FB Feedback voltage input pin Figure 2. Pin Configuration(s) Product structure : Silicon monolithic integrated circuit This product is not designed protection against radioactive rays www.rohm.com TSZ02201-0F2F0AG00020-1-2 2012 ROHM Co., Ltd. All rights reserved. 1/11 TSZ2211114001 21.JUN.2012 Rev.001Datasheet BU9002xNUX Series Block Diagram(s) MODE AVIN PWM/PFM TSD UVLO control PVIN C Current sense FB Switching L OUTPUT - + Control Logic LX C ERROR AMP and Gate Driver VREF EN Frequency PGND SHUTDOWN control ON/OFF AGND Figure 3. Block Diagram(s) Description of Block(s) The BU9002xNUX are a synchronous step-down DC/DC converter that achieves fast transient response from light load to heavy load by hysteretic PWM control system and current constant PFM control system. PWM control BU9002xNUX operates by hysteretic PWM control. This scheme ensures fast switching, high efficiency, and fast transient response. When the output voltage is below the VREF voltage, the error comparator output is low to high and turning on P-channel MOSFET until above the VREF voltage and minimum on time. PFM control At light load the regulator and MODE=low, the regulator operates with reduced switching frequency and improves the efficiency. During PFM operation, the output voltage slightly higher than typical output voltage. Figure 4. Operation of PFM mode and PWM mode w ww.rohm.com TSZ02201-0F2F0AG00020-1-2 2012 ROHM Co., Ltd. All rights reserved. 2/11 TSZ2211115001 21.JUN.2012 Rev.001