RP901K SERIES Synchronous Step-down DC/DC Converter with VD and VR NO.EA-156-121225 OUTLINE The RP901xxxx is a CMOS-based current mode PWM control synchronous step-down DC/DC converter with a voltage detector (VD) and an LDO regulator (VR). Each of Step-down DC/DC converters is composed of an oscillator, a voltage reference unit, an error amplifier, a switching control circuit, a soft-start circuit, a protection circuit, a UVLO circuit, a switching transistor. Due to the switching elements are built in and synchronous control, a high efficiency step-down DC/DC converter can be made with an inductor and capacitors. To realize high efficiency at light load, automatic PWM/VFM alternative mode can be selected other than the PWM fixed control mode. As protection circuits, a current limit circuit which limits Lx peak current cycle by cycle and a hiccup mode *1 protection circuit which works if the load current over the limit continues for a certain time are built in. The output voltage can be preset with 0.05V step in the factory due to the built-in feed back resistance, and the tolerance is 2%. Since the package is DFN (PLP) 2527-10, high density mounting on board is possible. Built-in LDO regulator (VR) is composed of a voltage reference unit, a voltage detecting resistor-network, an error amplifier, a short current limit circuit, and a driver transistor. After the soft-start time of the DC/DC converter *2 is over and a specified delay time, LDO starts up. The sequence function is fixed internally . Built-in voltage detector (VD) supervises the input voltage or the output of the VR (The reset function works for UVLO and over-current of the DC/DC converter). The option is preset in the factory. The output type is N-channel open drain. The released delay time is built-in, typ.50ms. If the junction temperature of the IC is over the limit, the system is reset by the built-in thermal shut-down circuit. *1) A version: As soon as the load current is over the limit, the system restarts by the protection. *2) C, D versions: No sequence function FEATURES Input Voltage Range 4.5V to 5.5V Supply Current Typ. 460A (at PWM mode) Typ. 170A (at light load applied to B, C, D versions) Step-down DC/DC Converter Output Voltage Range 1.2V to 1.8V, preset is possible by users request Output Voltage Tolerance 2% Oscillator Frequency Typ. 1.2MHz Built-in driver ON resistance Typ. P-channel 0.25, N-channel 0.25 (at V =5V) IN Soft-start function Typ. 1ms Lx peak current limit function Typ. 1.4A (D version: 1.5A) Output CurrentMin. 800mA (D version: 900mA) Protection Delay Time Typ. 0.1ms (applied to B, C, D versions) UVLO function Typ. 3.5V Chip enable function H active Ver. 1.0 1 RP901K LDO Regulator Output Voltage Range 2.5V to 3.3V, preset is possible by users request Output Voltage Tolerance 1.0% Output Current Min. 600mA Start-up delay time Typ. 2ms (applied to A, B versions) Auto-Discharge function at turning off Discharge resistance Typ.50 (at V =5V) IN VD Voltage Detector Threshold Range 2.0V to 3.0V, preset is possible by users request (A version: VR output voltage is supervised), 3.0V to 5.0V, preset is possible by users request (B, C, D versions: Input voltage is supervised Released Delay Time Typ.50ms Thermal shutdown circuit Detecting Temperature: Typ. 165 C, Released temperature: Typ. 110 C PackageDFN(PLP)2527-10 External Components C =10.0F, C =10.0F, L=4.7H (DC/DC), IN OUT1 C =2.2F(VR) OUT2 APPLICATION Optical Disk Equipment Ver. 2.5 2