RP508K Series 600 mA 6 MHz Synchronous Step-down DC/DC Converter NO. EA-318-171106 OUTLINE The RP508K is a low supply current PWM/VFM step-down DC/DC converter with synchronous rectifier (1) featuring 600 mA output current. Internally, a single converter consists of an oscillator, a reference voltage unit, an error amplifier, a switching control circuit, a mode control circuit, a soft-start circuit, an under-voltage lockout (UVLO) circuit, an over current protection circuit, a thermal shutdown circuit and switching transistors. By the adoption of the synchronous rectification circuit with built-in switching transistors, the RP508K works as efficient step-down DC/DC converter, without connecting external diodes. Using synchronous rectification not only increases circuit performance but also allows a design to reduce parts count. Power controlling method can be selected from forced PWM control type or PWM/VFM auto switching control type by inputting a signal to the MODE pin. In low output current, forced PWM control switches at fixed frequency rate in order to reduce noise. Likewise, in low output current, PWM/VFM auto switching control automatically switches from PWM mode to VFM mode in order to achieve high efficiency. Output voltage is internally fixed type which allows output voltages that range from 0.8 V to 3.3 V in 0.1 V step. The output voltage accuracy is as high as 1.5% or 18 mV. Protection circuits included in the RP508K are over current protection circuit and thermal shutdown circuit. Over current protection circuit supervises the inductor peak current in each switching cycle, and if the current exceeds the L current limit (I ), it turns off P-channel Tr. Thermal shutdown circuit detects overheating of X LXLIM the converter if the output pin is shorted to the ground pin (GND) etc. and stops the converter operation to protect it from damage if the junction temperature exceeds the specified temperature. The RP508K is offered in a small and thin 6-pin DFN(PLP)1212-6F package which achieves the smallest possible footprint solution on boards where area is limited. For an input capacitor (C ) and an output capacitor (C ), the smaller sized 0402/1005 (inch/mm) capacitor IN OUT can be used. For an inductor (L), the smaller sized 0603/1608 or 1005/2012 (inch/mm) inductor can be used. FEATURES Input Voltage Range (VIN) 2.3 V to 5.5 V (Absolute Maximum Ratings: 6.5 V) Output Voltage Range (VOUT) 0.8 V to 3.3 V (Adjustable in 0.1 V steps) Supply Current (IDD2) Typ. 15 A (VFM Mode with No-load) Standby Current (Istandby) Typ. 0 A Output Voltage Temperature Coefficient (VOUT/Ta) Typ. 100 ppm/C Oscillator Frequency (fosc) Typ. 6.0 MHz Maximum Duty Cycle (Maxduty) 100% Built-in Driver ON Resistance (RONP, RONN) Typ. Pch. 0.33 , Nch. 0.24 (VIN = 3.6 V) UVLO Detector Threshold (VUVLO01) Typ. 2.0 V Soft-start Time (tstart) Typ. 90 s (1) This is an approximate value. The output current is dependent on conditions and external components. 1 RP508K NO. EA-318-171106 LX Current Limit Circuit (ILXLIM) Typ. 1.1 A Output Voltage Accuracy 1.5% (VOUT 1.2 V) or 18 mV (VOUT < 1.2 V) Package DFN(PLP)1212-6F APPLICATIONS Cellular Phones Smartphones Digital Still Camera Notebook PCs, PDAs Li-ion Battery-used Equipment SELECTION GUIDE (1) The set output voltage and the auto discharge function are user-selectable options. Selection Guide Product Name Package Quantity per Reel Pb Free Halogen Free RP508Kxx1 -TR DFN(PLP)1212-6F 5,000 pcs Yes Yes (2) xx: Specify the set output voltage (VSET) within the range of 0.8 V (08) to 3.3 V (33) in 0.1 V steps . If the set output voltage includes the 3rd digit, indicate the digit of 0.01. (1.05 V, 1.25 V, 1.35 V) Ex. If the set output voltage is 1.05 V: RP508K101 5 If the set output voltage is 1.25 V: RP508K121 5 If the set output voltage is 1.35 V: RP508K131 5 : Specify the auto-discharge option. A: Fixed output voltage type B: Fixed output voltage type, auto-discharge function in shutdown mode (1) Auto-discharge function quickly lowers the output voltage to 0 V, when the chip enable signal is switched from the active mode to the standby mode, by releasing the electrical charge accumulated in the external capacitor. (2) 0.05 V step is also available as a custom code. 2