R1211x SERIES
STEP-UP DC/DC CONTROLLER
NO.EA-088-0604
OUTLINE
The R1211x Series are CMOS-based PWM step-up DC/DC converter controllers with low supply current.
Each of the R1211x Series consists of an oscillator, a PWM control circuit, a reference voltage unit, an error
amplifier, a reference current unit, a protection circuit, and an under voltage lockout (UVLO) circuit. A low ripple,
high efficiency step-up DC/DC converter can be composed of this IC with some external components, or an
inductor, a diode, a power MOSFET, divider resisters, and capacitors.
Phase compensation has been made internally in the R1211x002B/D Series, while phase compensation can
be made externally as for R1211x002A/C Series. B/D version has stand-by mode.
Max duty cycle is internally fixed typically at 90%. Soft start function is built-in, and Soft-starting time is set
typically at 9ms(A/B, 700kHz version) or 10.5ms(C/D, 300kHz version). As for the protection circuit, after the
soft-starting time, if the maximum duty cycle is continued for a certain period, the R1211x Series latch the
external driver with its off state, or Latch-type protection circuit works.
The delay time for latch the state can be set with an external capacitor.
To release the protection circuit, restart with power-on (Voltage supplier is equal or less than UVLO detector
threshold level), or once after making the circuit be stand-by with chip enable pin and enable the circuit again.
FEATURES
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Standby Current ................................................Typ. 0µA (for B/D version)
Input Voltage Range .........................................2.5V to 6.0V
Built-in Latch-type Protection Function (Output Delay Time can be set with an external capacitor)
Two Options of Basic Oscillator Frequency ......300kHz, 700kHz
Max Duty Cycle.................................................Typ. 90%
High Reference Voltage Accuracy ....................±1.5%
U.V.L.O. Threshold level ...................................Typ. 2.2V (Hysteresis Typ. 0.13V)
Small Packages ................................................SOT-23-6W or thin (package height Max. 0.85mm) SON-6
APPLICATIONS
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Constant Voltage Power Source for portable equipment.
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Constant Voltage Power Source for LCD and CCD.
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RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
