NCP4354ADR2G Datasheet, PDF (12/17 Pages) ON Semiconductor – Secondary Side SMPS OFF Mode Controller for Low Standby Power

NCP4353, NCP4354
load in OFF mode. When an output load is applied, capacitor
C1 is discharged faster and this creates a voltage drop at D8.
When there is enough voltage at D8, T2 is opened and
current is injected into the OFFDET divider through R17.
OFFDET voltage higher than 10% of V_CC ends OFF mode
and ON/OFF current stops. Primary controller leaves OFF
D2
OFF Supply
D1
C1
C2
Feedback
&
ON / OFF
Opto
R1
VCC
C3
C4
R10
R2
DRIVE
VCC
management
VDD
VREF
IDRIVEOFF
Power
RESET
SW1
GND
mode because voltage at its FB pin rises above OFF mode
end level and switching resumes.
Normal operation waveforms for typical load detection
connection and improved load detection waveforms are
shown in Figure 33.
R4
VOUT
Power
RESET
QS
QR
IBIASV
VDD
SW3
Sink only
OTA
Voltage
Regulation
VREF
0.9 x VREF
R7
VSNS
R8
R5
IBIASV
Enabling
Off Mode
Detection
VCC
10%VCC
OFFDET
Power RESET
Min Output
Voltage
VREFM
VMIN
R6
R9
Figure 27. Typical Application Schematic for NCP4353B
D2
OFF Supply
D1
C1
C2
Feedback
&
ON / OFF
Opto
R1
VCC
C3
C5
C4
R11
R10
R2
FBC
ON/OFF
ON / OFF
LED
R3
LED
GND
VCC
management
VDD
VREF
IDRIVEOFF
Power
RESET
SW1
Power
RESET
Current
Regulation
Sink only
OTA
VDD
IBIASV
VREFC
SW3
Sink only
OTA
Voltage
Regulation
VREF
0.9 x VREF
ISNS
R4
R13
VOUT
R7
VSNS
R5
R12
R8
QS
QR
IBIASV
Enabling
Off Mode
Detection
VCC
10%VCC
OFFDET
SW2
1 kHz, 12% D.C.
Oscillator
VMIN
Power RESET
Min Output
Voltage
VREFM
R6
R9
Figure 28. Typical Application Schematic for All Features
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