L2800(Old_V) 데이터 시트보기 (PDF) - Unisonic Technologies
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L2800 Datasheet PDF : 9 Pages
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UTC L2800 LINEAR INTEGRATED CIRCUIT
PARAMETER
Output Current Setting Pin Voltage
Section/Control Section Input Off Condition
Input On Condition
Pin Current Range
Entire Device
Stand-by Current
Average Supply Current
SYMBOL
VBR
IOFF
ION
IBR
ICCS
ICC
TEST CONDITIONS
RB=390Ω
BR/CTL pin open or Vcc
RB=390Ω
MIN TYP MAX UNIT
0.2 0.3 0.4 V
-20
0 µA
-45 µA
-1.8
-0.1 mA
1 µA
5.5 9.3 mA
DIAGRAM
FB pin voltage
Reference input for short
circuit detection comparator
Idle period setting voltage
Sawtooth wave output
Soft start setting voltage
OUT pin waveforms
SCP pin waveforms
ON
Power supply control SW
OFF
Soft start
ts
Output
short
circuit
tPE
Output short circuit
Short circuit
detection
HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT
DETECTION
1.SOFT START
At power on, the capacitor CPE connected to the SCP pin starts charging. The PWM comparator compares the
soft start setting voltage as a proportion of the voltage at the SCP pin with the sawtooth waveform. The
comparison controls the ON duty of the OUT pin, causing the soft start operation. On completion of soft start
operation, the voltage at the SCP pin stays low, the soft start setting voltage stays high, and the circuit enters the
output short circuit detection wait state.
Soft start time (The time until the output ON duty reaches approximately 50%)
ts[S]≒0.35*CPE[µF]
2.SHORT CIRCUIT PROTECTION
If the switching regulator output suddenly drops due to load effect, the error amplifier output (FB pin) is fixed at
VOM+ and capacitor CPE starts charging. When the voltage at the SCP pin reaches approximately 0.8V,the output
pin is set low and the SCP pin stays low.
Once the protection circuit operates, the circuit can be restored by resetting the power supply.
• Short circuit detection time
tPE[S]≒0.8*CPE[µF]
UTC
UNISONIC TECHNOLOGIES CO., LTD. 4
QW-R121-010,A
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