2A PWM/VFM Step-down DC/DC Converter with Synchronous Rectifier
The RP506x are low supply current CMOS-based PWM/VFM step-down DC/DC converters with synchronous rectifier featuring 2A*1 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, a latch type protection circuit, an under-voltage lockout (UVLO) circuit, a thermal shutdown circuit, and switching transistors.
The RP506x is employing synchronous rectification for improving the efficiency of rectification by replacing diodes with built-in switching transistors. 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 type can be selected from an internally fixed output voltage type (RP506Kxx1A/B/D/E) or an externally adjustable output voltage type (RP506K001C/F). The output voltage of the RP506Kxx1A/B/D/E can be set by 0.1V step and the output voltage accuracy is as high as ±1.5% or ±18mV. The output voltage of the RP506K001C/F can be set by using the external resistors.
Oscillator frequency can be selected from 2.25MHz (RP506Kxx1A/B/C) or 1.2MHz (RP506Kxx1D/E/F). Softstart time is Typ. 0.15ms, and by connecting an external capacitor to the TSS pin, soft-start time is adjustable.
Power good (PG) function monitors the VOUT pin voltage or the feedback pin voltage (VFB), and switches the PG pin to low if any abnormal condition is detected.
Protection circuits included in the RP506x are over current protection circuit, latch type 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 Pch Tr. Latch type protection circuit latches the built-in driver to the OFF state and stops the operation of the step-down DC/DC converter if the over current status continues or VOUT continues being the half of the setting voltage for equal or longer than protection delay time (tprot). 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 RP506x is available in DFN(PLP)2527-10 which achieves high-density mounting on boards.
- *1 This is an approximate value. The output current depends on conditions and external components.
|Supply Current||Typ. 48 µA (VFM mode, Lx at no load)|
|Standby Current||Typ. 0 µA|
|Input Voltage Range||2.5V to 5.5V (Absolute Maximum Ratings: 6.5V)|
|Output Voltage Range*2||
|Output Voltage Accuracy||±1.5% (VSET*3>=1.2V),
±18 mV (VSET<1.2V) (RP506Kxx1A/B/D/E)
|Feedback Voltage Accuracy||±9 mV (VFB=0.6V) (RP506K001C/F)|
|Output Voltage/Feedback Voltage Temperature Coefficient||±100 ppm/ ºC|
|Oscillator Frequency||Typ. 2.25 MHz (RP506Kxx1A/B/C)
Typ. 1.2 MHz (RP506Kxx1D/E/F)
|Oscillator Maximum Duty||Min. 100%|
|Built-in Driver ON Resistance||Typ. Pch. 0.130Ω, Nch. 0.125Ω (VIN=3.6V)|
|UVLO Detector Threshold||Typ. 2.2 V|
|Inductor Current Limit Circuit||Current limit Typ. 2.8 A|
|Latch Type Protection Circuit||Typ. 1.5 ms|
- *2Refer to Selection Guide for detailed information.
Fixed output voltage type (RP506Kxx1A/B/D/E) can be set up to 3.3V by 0.1V step.
Adjustable output voltage type (RP506K001C/F) can be set up to 4.0V.
- *3VSET=Set Output Voltage
- •Power source for Li-ion battery-used equipment
- •Power source for portable communication equipment, camcorder, DSC, Notebook PC
- •Power source for HDD, WLAN
|Data Sheet||Flyer||Design Guide|
|Package Info.||Mark Info.||Quality Assurance Data|
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