NCP1252BDR2G ON Semiconductor, NCP1252BDR2G Datasheet - Page 12

• Manufacturer Part Number: NCP1252BDR2G
• Description: IC PWM CTLR CURRENT MODE 8-SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1252BDR2G

• Frequency - Max: 500kHz
• Pwm Type: Current Mode
• Number Of Outputs: 1
• Duty Cycle: 84%
• Voltage - Supply: 9 V ~ 28 V
• Buck: No
• Boost: No
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -25°C ~ 125°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Duty Cycle (max): 80 %
• Mounting Style: SMD/SMT
• Switching Frequency: 92 KHz to 550 KHz
• Maximum Operating Temperature: + 125 C
• Fall Time: 22 ns
• Rise Time: 26 ns
• Synchronous Pin: No
• Topology: Flyback, Forward
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

and the SS pin is internally grounded in order to discharge
the soft start capacitor connected to this pin (Case #3). If the
BO pin is released, when its level reaches the V
new soft start sequence happens.
DRV pin
V
When the BO pin is grounded, the controller is shut down
V
BO pin
SS pin
CC
CC(on)
V
pin
BO
Rse nse
Soft start
Rcomp
Figure 31. Controller Shuts Down with the Brown Out Pin
CASE #3
SS capacitor is
discharged
CS
SS
Iss
Vdd
Figure 32. Soft Start Principle
Soft Start
Status
BO
http://onsemi.com
level a
Time
Time
Time
Time
120 ms
Fixe d
Delay
LEB
12
Grand Reset
Soft Start:
the SS pin voltage divided by 4 controls the peak current
sensed on the CS pin. Thus as soon as the CS pin voltage
becomes higher than the SS pin voltage divided by 4 the
driver latch is reset.
DRV pin
V
V
BO pin
SS pin
As illustrated by the following figure, the rising voltage on
CC
CC(on)
V
1/4
pin
BO
UVLO
+
−
Clock
Soft start
S
R
Q
Q
CASE #4
DRV
Time
Time
Time
Time