Rev. 1.12

- 11 -

µF

for stable operation.

µF tantalum type is recommended.

Internal Oscillator Waveform

Internal Operational

Amplifier Output

Internal Soft-start

Set Voltage

Lx Pin Output

Soft-start Time

Stable

Output

Short

Delay Time of Protection

Latched

CE pin Voltage

Output Short

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.

1) Output Voltage vs. Output Current

1.7

1.72

1.74

1.76

1.78

1.8

1.82

1.84

1.86

1.88

1.9

1

10

100

1000

Vin=3.3V PWM

Vin=3.3V VFM

Vin=5.0V PWM

Vin=5.0V VFM

R1230D181A