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RP505K SERIES
1A Step-down DC/DC Converters with synchronous rectifier
NO.EA-273-110519
1
OUTLINE
The RP505K Series are low supply current CMOS-based 1A
step-down DC/DC Converters with synchronous
rectifier.Each of these ICs 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 lock out (UVLO)
circuit, a thermal shutdown circuit, and a switching transistors. A low ripple, high efficiency synchronous rectifier
step-down DC/DC converter can be easily composed of this IC with only an inductor and capacitors. Since the
package is DFN(PLP)2020-8, high density mounting on boards is possible.
In the RP505K series, as for the A version and B version, since feedback resistors are built-in, the voltage is
fixed internally. 0.1V step output can be set by laser-trim and
±1.5%(VOUT≥1.2V) or 18mV(VOUT<1.2V) tolerance is
guaranteed. As for the C version, output voltage is adjustable with external divider resisters.
Mode alternative circuit works automatically for improving the efficiency. Considering fixed noise frequency,
PWM fixed control type is also available. In other words, one mode is the PWM/VFM alternative mode, the other
is forced PWM fixed mode.
As protection circuits, the RP505K Series contain a current limit circuit which limits the Lx peak current in each
clock cycle, and a latch type protection circuit which latches the built-in driver to the OFF state if the load current
exceeds the limit value or the output short continues for a specified time (the protection delay time). The latch
protective circuit can be released by once putting the IC into the standby mode with the CE pin and then into 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 protective circuit. The RP505K Series also contain a thermal shutdown
circuit which detects the overheating and resets the IC when the junction temperature of the RP505K Series
exceeds the specified temperature.
)This is an approximate value, because output current depends on conditions and external parts.
FEATURES
Supply Current ...................................................... Typ. 40μA(at VFM mode, at no load)
Standby Current .................................................... Max. 5μA
Input Voltage Range ............................................. 2.3V to 5.5V (Absolute maximum rating; 6.5V)
Output Voltage Range(Ver.A,B) ............................ 0.6V to 3.3V
(With a 0.1V step, as for 0.8V or less, input voltage range is limited.)
(Ver.C) ............................... 0.8V to 3.3V
Output Voltage Accuracy(Ver.A,B) ........................ ±1.5% (VOUT≥1.2V), ±18mV (VOUT<1.2V)
Feedback Voltage Accuracy(Ver.C) ...................... ±9mV(VFB=0.6V)
Temperature-Drift Coefficient of Output Voltage/Feedback
.............................................................................. Typ.
±100ppm/°C
Oscillator Frequency ............................................. Typ. 2.25MHz
Oscillator Maximum Duty Cycle............................ Min. 100%
Built-in Driver ON Resistance ............................... Typ. Pch. 0.23、Nch. 0.20(VIN=3.6V)
UVLO Detector Threshold..................................... Typ. 2.0V
Soft-start Time....................................................... Typ. 0.15ms
LX Current Limit Circuit.......................................... Typ. 1.7A
Latch Type Protection Circuit ................................ Typ. 1.5ms
Package ................................................................ DFN(PLP)2020-8