RP550K001A 1A PWM/VFM Dual Step-down DC/DC Converter with Synchronous Rectifier No.EA-285-210909 OUTLINE *1 The RP550K001A is a CMOS-based 1A dual step-down DC/DC converter with synchronous rectifier. Internally, a single converter consists of oscillators, reference voltage units, error amplifiers, switching control circuits, soft-start circuit, latch type protection circuit, an under voltage lockout (UVLO) circuit, a thermal shutdown circuit and switching transistors. Replacing diodes with built-in switching transistors improves the efficiency of rectification. Therefore, by simply using two inductors, resistors and capacitors as the external components, a low ripple high efficiency synchronous rectifier step-down DC/DC converter can be easily configured. Latch type protection circuit latches the built-in driver to the OFF state during high load or if the output is short-circuited for a specified time (protection delay time). The latch protection circuit can be released by once setting the converter into the standby mode with the CE pin and then setting it back to the active mode, or, by turning the power off and back on. Setting the supply voltage lower than the UVLO detector threshold can also release the latch protection circuit. Thermal shutdown circuit detects overheating of the converter and stops the converter operation to protect it from damage if the junction temperature exceeds the specified temperature. By inputting a signal to the MODE pin, the RP550K001A can choose PWM/VFM auto switching control or forced PWM control. In low output current, PWM/VFM auto switching control automatically switches from PWM mode to VFM mode in order to achieve high efficiency. Likewise, in low output current, forced PWM control switches at fixed frequency in order to reduce noise. When the both converters are in PWM control, the converters operate with 180 turn-on phase shift of the switching transistors. The RP550K001A is available in DFN(PLP)2730-12 package which achieves high-density mounting on boards. *1 This is an approximate value, because output current depends on conditions and external components. FEATURES Supply Current Typ. 45A (VFM mode with no load/ 1 channel) Standby Current Max. 10A Input Voltage Range 2.3V to 5.5V (VSET 0.8V) Output Voltage Range Adjustable from 0.6V (Recommended range is up to 3.3V) Feedback Voltage Accuracy 9mV (VFB=0.6V) Output Voltage Temperature Coefficient 100ppm/C Oscillator Frequency Typ. 2.25MHz Oscillator Maximum Duty Min. 100% Built-in Driver ON Resistance Typ. Pch. 0.25, Nch. 0.21 (VIN=3.6V) UVLO Detector Threshold Typ. 2.0V Soft Start Time Typ. 0.2ms Lx Current Limit Circuit Typ. 1700mA/ channel Latch Type Protection Circuit Typ. 1.5ms Package DFN(PLP)2730-12 1 RP550K001A APPLICATION Power source for battery-powered equipment Power source for hand-held communication equipment, cameras, and VCRs Power source for Wireless LAN terminals BLOCK DIAGRAM SLOPE CURRENT IN V COMPENSATION FEEDBACK CHIP CE1 ENABLE CURRENT X1 L PROTECTION SWITCHING VFB1 CONTROL PGND1 SOFTSTART PWM / VFM CONTROL VREF CLK 0 AGND UVLO THERMAL OSCILLATOR PROTECTION PROTECTION MODE CLK 180 SLOPE CURRENT VIN COMPENSATION FEEDBACK CHIP CE2 ENABLE CURRENT LX2 PROTECTION SWITCHING VFB2 CONTROL CLK 180 PGND2 SOFTSTART PWM / VFM CONTROL VREF Figure 1. RP550K001A 2