RP504x Series
600 mA PWM/VFM Step-Down DC/DC Converter with Synchronous Rectifier
NO.EA-259-150130
OUTLINE
The RP504x is a low supply current CMOS-based PWM/VFM step-down DC/DC converter with synchronous
rectifier featuring 600 mA*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 (RP504xxx1A/D), a soft-start
circuit, a Latch-type protection circuit, an under voltage lockout (UVLO) circuit a.nd switching transistors.
The RP504x 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 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 RP504x are overcurrent protection circuit and latch type protection circuit.
Overcurrent 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. 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 overcurrent status continues or
VOUT continues being the half of the setting voltage for equal or longer than protection delay time (tprot). To cancel
the latch type protection circuit, select the standby mode or the active mode with the CE pin, or drop the power
supply voltage below the UVLO detector threshold.
The RP504x is offered in 6-pin DFN(PLP)1216-6F, 6-pin DFN1616-6B and 5-pin SOT-23-5 packages which
achieve the smallest possible footprint solution on boards where area is limited.
*1 This is an approximate value. The output current is dependent on conditions and external components.
1