As for CIN, use a capacitor with low ESR (Equivalent Series Resistance) Ceramic type of a capacity at least 10µF
for stable operation.
COUT can reduce ripple of Output Voltage, therefore as much as 10µF tantalum type is recommended.
ꢀ TIMING CHART
CE pin Voltage
Output
Short
Output Short
Internal Soft-start
Set Voltage
Internal Operational
Amplifier Output
Internal Oscillator Waveform
Lx Pin Output
Latched
Delay Time of Protection
Stable
Soft-start Time
The timing chart as shown above describes the waveforms starting from the IC is enabled with CE and latched with
protection. During the soft-start time, until the level is rising up to the internal soft-start set voltage, the duty cycle of Lx
is gradually wider and wider to prevent the over-shoot of the voltage. During the term, the output of amplifier is “H”,
then after the output voltage reaches the set output voltage, they are balanced with the stable state. Herein, if the
output pin would be short circuit, the output of amplifier would become “H” again, and the condition would continue for
1.5ms (TYP.), latch circuit would work and the output of Lx would be latched with “OFF”. (Output =“High-Z”)
If the output short is released before the latch circuit works (within 1.5ms after output shorted), the output of amplifier
is balanced in the stable state again.
Once the IC is latched, to release the protection, input “L” with CE pin, or make the supply voltage at UVLO level or
less.
ꢀ TYPICAL CHARACTERISTICS
1) Output Voltage vs. Output Current
1.9
1.88
R1230D181A
1.86
1.84
1.82
Vin=3.3V PWM
Vin=3.3V VFM
Vin=5.0V PWM
Vin=5.0V VFM
1.8
1.78
1.76
1.74
1.72
1.7
1
10
100
1000
Output Current IOUT[mA]
Rev. 1.12
- 11 -
RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
