NCP1251 View Datasheet(PDF) - ON Semiconductor
Part Name
Description
MFG CO.
NCP1251 Datasheet PDF : 24 Pages
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NCP1251
ELECTRICAL CHARACTERISTICS
(For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, Max TJ = 150°C, VCC = 12 V unless otherwise noted)
Symbol
Rating
Pin Min Typ Max Unit
INTERNAL OSCILLATOR
fOSC
Oscillation frequency (65 kHz version)
fOSC
Oscillation frequency (100 kHz version)
Dmax Maximum duty−cycle
fjitter
Frequency jittering in percentage of fOSC
fswing Swing frequency
FEEDBACK SECTION
−
61
65
71 kHz
−
92 100 108 kHz
−
76
80
84
%
−
±5
%
−
240
Hz
Rup
Internal pull−up resistor
Req
Equivalent ac resistor from FB to GND
Iratio
Pin 2 to current setpoint division ratio
Vfreeze Feedback voltage below which the peak current is frozen
FREQUENCY FOLDBACK
2
20
kW
2
16
kW
−
4.2
2
1.05
V
Vfold
Frequency foldback level on the feedback pin – [45% of maximum peak current
−
1.5
V
Ftrans Transition frequency below which skip−cycle occurs
−
22
26
30 kHz
Vfold,end End of frequency foldback feedback leve, Fsw = Fmin
350
mV
Vskip
Skip−cycle level voltage on the feedback pin
−
300
mV
Skip Hysteresis on the skip comparator – (Note 5)
hysteresis
−
30
mV
INTERNAL SLOPE COMPENSATION
Vramp Internal ramp level @ 25°C – (Note 7)
Rramp Internal ramp resistance to CS pin
PROTECTIONS
4
2.5
V
4
20
kW
Vlatch
Tlatch−blank
Tlatch−count
Tlatch−del
Timer
Latching level input
Blanking time after drive turn off
Number of clock cycles before latch confirmation
OVP detection time constant
Internal auto−recovery fault timer duration
3 2.7
3
3.3
V
1
1.0
ms
−
4.0
1
600
ns
− 100 130 160 ms
VOVP Latched Over voltage protection on the VCC rail
5
24 25.5 27
V
TOVPdel Delay before OVP on VCC confirmation
5
20
ms
4. For design robustness, we recommend to inject 60 mA as a minimum at the lowest input line voltage.
5. Guaranteed by design
6. See characterization table for linearity over negative bias voltage
7. A 1 MW resistor is connected from pin 3 to the ground for the measurement.
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