R1232D Datasheet, PDF (1/24 Pages) RICOH electronics devices division – PWM STEP-DOWN DC/DC CONVERTER WITH SYNCHRONOUS RECTIFIER

R1232D SERIES
PWM STEP-DOWN DC/DC CONVERTER WITH SYNCHRONOUS RECTIFIER
NO.EA-129-0606
OUTLINE
The R1232D Series are CMOS-based PWM step-down DC/DC converters with synchronous rectifier, low
supply current. As an output capacitor, a 10µF or more ceramic capacitor can be used with the R1232D.
Each of these ICs consists of an oscillator, a PWM control circuit, a voltage reference unit, an error amplifier, a
soft-start circuit, protection circuits, a protection against miss operation under low voltage (UVLO), a chip enable
circuit, a synchronous rectifier, Nch. driver transistor, and so on. A low ripple, high efficiency step-down DC/DC
converter can be easily composed of this IC with only a few kinds of external components, or an inductor and
capacitors. (As for R1232D001x type, divider resistors are also necessary.) In terms of the output voltage, it is
fixed internally in the R1232Dxx1x types. While in the R1232D001x types, the output voltage is adjustable with
external divider resistors.
As protection circuits, current limit circuit which limits peak current of LX at each clock cycle, and latch type
protection circuit exist. The latch protection works if the term of the over-current condition keeps on a certain time.
Latch-type protection circuit works to latch an internal driver with keeping it disable. To release the condition of
protection, after disable this IC with a chip enable circuit, enable it again, or restart this IC with power-on or make
the supply voltage at UVLO detector threshold level or lower than UVLO.
FEATURES
• Two choices of Oscillator Frequency ............................ 1MHz, 2.25MHz
(Small inductors can be used. 4.7µH for 1MHz/2.2µH for 2.25MHz)
• Built-in Driver ON Resistance ....................................... P-channel 0.2Ω (at VIN=5.0V)
• Built-in Soft-start Function............................................. Typ. 1.0ms (fosc=1MHz type)
• Output Voltage .............................................................. 0.9V to 3.3V (xx1x Type)
0.8V to VIN (001x Type)
• High Accuracy Output Voltage ......................................±2.0%
• Built-in Current Limit Circuit .......................................... Typ. 1.4A
• Package ........................................................................SON-8 (t=0.9mm)
APPLICATIONS
• Power source for portable equipment such as PDA, DSC, Notebook PC.
• Power source for HDD
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