PWM/VFM step-down DC/DC converter with Synchronous

Rectifier

R1230D Series

2001. Sep. 8

Rev. 1.12

- 1 -

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s OUTLINE

The R1230D Series are PWM step-down DC/DC Converters with synchronous rectifier, low supply current by CMOS

process.

Each of these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a

soft-start circuit, protection circuits, a protection against miss operation under low voltage (UVLO), PWM/VFM

alternative circuit, a chip enable circuit, and a driver transistor. 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 R1230D001C/D types, divider resistors are also necessary.) In terms of Output Voltage, it is fixed

internally in the R1230DXX1A/B types. While in the R1230D001C/D types, Output Voltage is adjustable with external

divider resistors.

PWM/VFM alternative circuit is active with Mode Pin of the R1230D Series. Thus, when the load current is small,

the operation can be switching into the VFM operation from PWM operation by the logic of MODE pin and the

efficiency at small load current can be improved. As protection circuits, Current Limit circuit which limits peak current

of Lx at each clock cycle, and Latch type protection circuit which works if the term of Over-current condition keeps on

a certain time in PWM mode exist. 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.

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s FEATURES

q Built-in Driver ON Resistance

q Built-in Soft-start Function (TYP. 1.5ms), and Latch-type Protection Function (Delay Time; TYP. 1.5ms)

q Two choices of Oscillator Frequency

• • • • • • 500kHz, 800kHz

q PWM/VFM alternative with MODE pin

• • • • • • PWM operation; MODE pin at “L”,

VFM operation; MODE pin at “H”

q High Efficiency

• • • • • • • • • • • • • • • • • • TYP. 90%

q Output Voltage

• • • • • • • • •Stepwise Setting with a step of 0.1V in the range of 1.2V ∼ 4.0V(XX1A/B Type)

q High Accuracy Output Voltage

• • • • • • • • • •±2.0%(XX1A/B Type)

q Package

• • • • • SON8 (Max height 0.9mm, thin type)

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s APPLICATIONS

q Power source for portable equipment.