Datasheet Single-chip Type with Built-in FET Switching Regulator Series 1.0A, Step-down Switching regulators with Built-in Power MOSFET BU90054GWZ General Description Applications The BU90054GWZ are a high efficiency 6MHz Smart phones, Cell phones, Portable applications and synchronous step-down switching regulator with ultra Micro DC/DC modules, USB accessories low current PFM mode. It provides up to 1.0A load current and an input voltage Package(s) W(Typ.) x D(Typ.) x H(Max.) range from 3.0V to 5.5V, optimized for battery powered UCSP30L1 1.30mm x 0.90mm x 0.33mm portable applications. BU90054GWZ 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 Typical Application Circuit(s) load current. 1.0uH Features VIN LX VOUT Fast transient response Automatic PFM/PWM operation 2.35.5V 4.7uF Forced PWM operation 4.7uF EN FB Internal Soft Start Under voltage lockout Over current protection GND MODE Thermal shutdown Figure 1. Typical Application Circuit(s) Lineup Operating mode Output Part No. Input voltage Switching frequency voltage MODE=L MODE=H Automatic BU90054GWZ 1.80V 2.3V to 5.5V 4.8MHz to 6.0MHz Forced PWM PFM/PWM Pin Configuration(s) Pin Description(s) (BOTTOM VIEW) Pin No. Symbol Function B1 B2 B3 A1 VIN Power supply input pin MODE LX FB A2 EN Enable pin A3 GND GND pin A1 A2 A3 VIN EN GND B1 MODE Forced PWM mode pin B2 LX Inductor connection pin B3 FB Feedback voltage input pin Figure 2. Pin Configuration(s) Product structureSilicon monolithic integrated circuit This product is not designed protection against radioactive rays www.rohm.com TSZ02201-0F1F0AG00060-1-2 2014 ROHM Co., Ltd. All rights reserved. 1/15 TSZ2211114001 8.Dec.2014 Rev.002 BU90054GWZ Block Diagram(s) L PWM/PFM MODE H PWM MODE MODE B1 VIN A1 2.3 5.5V PWM/PFM TSD UVLO control FB VOUT B3 EN 1.50.47uH Switching - B2 VOUT + Control Logic 4.7uF and LX ERROR COMP Gate Driver VREF EN Frequency H ON SHUTDOWN A2 L OFF control GND A3 Figure 3. Block Diagram(s) Description of Block(s) The BU90054GWZ 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 BU90054GWZ 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. output PWM mode voltage PFM (constant current) Threshold. Turn off Pch FET PFM Threshold. Turn on Pch FET PFM Mode at Light Load PWM Mode at Moderate to Heavy Loads Figure 4. Operation of PFM mode and PWM mode www.rohm.com TSZ02201-0F1F0AG00060-1-2 2014 ROHM Co., Ltd. All rights reserved. 2/15 TSZ2211115001 8.Dec.2014 Rev.002