2001.8.30
Step-up DC/DC Controller
R1211X Series
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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.
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FEATURES
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Standby Current
• • • • • • • • • • • • • • • • •
TYP. 0µA (for B/D version)
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Input Voltage Range
• • • • • • • • • • • • • • •
2.5V to 6.0V
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Built-in Latch-type Protection Function (Output Delay Time can be set with an external capacitor)
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Two Options of Basic Oscillator Frequency
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300kHz, 700kHz
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Max Duty Cycle
• • • • • • • • • • • • • • • • • •
Typ. 90%
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High Reference Voltage Accuracy
• • • • • • • ±1.5%
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U.V.L.O. Threshold level
• • • • • • • • • • • • •
Typ. 2.2V (Hysteresis TYP. 0.13V)
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Small Package
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SOT-23-6W or thin (package height MAX. 0.85mm) SON-6 (Under Development)
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APPLICATIONS
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Constant Voltage Power Source for portable equipment.
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Constant Voltage Power Source for LCD and CCD.
Rev. 1.10
-1-
RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
