NCP1253
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
CURRENT COMPARATOR
Vfold
Default internal voltage set point for frequency foldback trip point – 45% of 4
Vlimit
Vfreeze Internal peak current setpoint freeze (≈31% of Vlimit)
4
TDEL
Propagation delay from current detection to gate off−state
4
TLEB
Leading Edge Blanking Duration
4
TSS
Internal soft−start duration activated upon startup, auto−recovery
−
357
mV
250
mV
100
150
ns
300
ns
4
ms
INTERNAL OSCILLATOR
fOSC
Oscillation frequency (65 kHz version)
fOSC
Oscillation frequency (100 kHz version)
Dmax
Maximum duty−ratio
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(FB) 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
Vfold,end
Vskip
Skip
hysteresis
Transition frequency below which skip−cycle occurs
End of frequency foldback feedback level, Fsw = Fmin
Skip−cycle level voltage on the feedback pin
Hysteresis on the skip comparator
−
22
26
30
kHz
350
mV
−
300
mV
−
30
mV
INTERNAL SLOPE COMPENSATION
Vramp
Internal ramp level @ 25°C (Note 4)
4
2.5
V
Rramp Internal ramp resistance to CS pin
4
20
kW
4. A 1 MW resistor is connected from pin 4 to the ground for the measurement.
PROTECTIONS
VOVP
TOVPdel
Timer
Latched Overvoltage Protection on the VCC rail
Delay before OVP confirmation on the VCC rail
Internal auto−recovery fault timer duration
5
24
25.5
27
V
5
20
ms
−
100
130
160
ms
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