Nisshinbo Micro Devices Inc. RP508K331B-TR

The RP508K is a low supply current PWM/VFM step-down DC/DC converter with synchronous rectifier 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 Lx current limit (ILxLIM), it turns off P-channel Tr. Thermal shutdown circuit detects overheating of 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(PL)1212-6F package which achieves the smallest possible footprint solution on boards where area is limited. For an input capacitor (CIN) and an output capacitor (COUT), the smaller sized 0402/1005 (inch/mm) capacitor can be used. For an inductor (L), the smaller sized 0603/1608 or 1005/2012 (inch/mm) inductor can be used.

• 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 μA (VFM Mode with No-load)
• Standby Current (Istandby): Typ. 0 μA
• 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 Ω, Nch. 0.24 Ω (VIN = 3.6 V)
• UVLO Detector Threshold (VUVLO01): Typ. 2.0 V
• Soft-start Time (tstart): Typ. 90 μs
• 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(PL)1212-6F

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