NJU7678
■BLOCK DIAGRAM
V+
FB
IN-
1V Vref
ER⋅AMP
Soft Start
Latch
UVLO
SCP
1V
2µA
SCP
2kΩ
0.5
A
RT
1V
DTC
0.65V
0.15V
OSC
0.5V
PWM
Buffer
0.6V
RT
RT
GND
DRAIN
DRAIN
DRAIN
SOURCE
SOURCE
SOURCE
SOURCE
The initial soft start time is 4msec. The soft start time can be adjusted by connecting the capacitor with
the DTC pin. The charging current is calculated by 0.5/RT.
The MaxDuty is 90%@700kHz. MaxDuty can be adjusted by connecting resistance with the DTC pin.
MaxDuty is calculated by (RDTC / RT) × 86 - 24.
The short-circuit protection circuit is a timer latch type. The protection Delay time can be adjusted with
the capacitor connected with the SCP pin. To release the latch mode, it should do reclosing the power
supply (below the UVLO detection voltage) or the SCP pin down to GND level.
-2-
Ver.2010-10-26