R1230D251B-TL RICOH [RICOH electronics devices division], R1230D251B-TL Datasheet - Page 11

• Manufacturer Part Number: R1230D251B-TL
• Description: PWM/VFM Step-down DC/DC Converter with Synchronous Rectifier
• Manufacturer: RICOH [RICOH electronics devices division]

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.
Rev. 1.12
As for C
for stable operation.
C
1) Output Voltage vs. Output Current
TIMING CHART
TYPICAL CHARACTERISTICS
Lx Pin Output
OUT
CE pin Voltage
1.88
1.86
1.84
1.82
1.78
1.76
1.74
1.72
1.9
1.8
1.7
Soft-start Time
can reduce ripple of Output Voltage, therefore as much as 10 F tantalum type is recommended.
1
IN
Internal Oscillator Waveform
, use a capacitor with low ESR (Equivalent Series Resistance) Ceramic type of a capacity at least 10 F
Internal Operational
Amplifier Output
10
Output Current I
Internal Soft-start
Set Voltage
Stable
- 11 -
OUT
[mA]
100
Output
Short
Output Short
Delay Time of Protection
1000
R1230D181A
Vin=3.3V PWM
Vin=3.3V VFM
Vin=5.0V PWM
Vin=5.0V VFM
Latched