NCP1253

www.onsemi.com

5

ELECTRICAL CHARACTERISTICS

Symbol

Unit

Max

Typ

Min

Pin

Rating

CURRENT COMPARATOR

Default internal voltage set point for frequency foldback trip point – 45% of

4

357

mV

Internal peak current setpoint freeze (

4

250

mV

Propagation delay from current detection to gate off−state

4

100

150

ns

Leading Edge Blanking Duration

4

300

ns

TSS

Internal soft−start duration activated upon startup, auto−recovery

−

4

ms

INTERNAL OSCILLATOR

Oscillation frequency (65 kHz version)

−

61

65

71

kHz

Oscillation frequency (100 kHz version)

−

92

100

108

kHz

Maximum duty−ratio

−

76

80

84

%

−

±5

%

Swing frequency

−

240

Hz

Feedback Section

Internal pull−up resistor

2

20

k

W

Equivalent ac resistor from FB to GND

2

16

k

W

Pin 2 to current setpoint division ratio

−

4.2

Feedback voltage below which the peak current is frozen

2

1.05

V

FREQUENCY FOLDBACK

Frequency foldback level on the feedback pin –

≈45% of maximum peak

current

−

1.5

V

Transition frequency below which skip−cycle occurs

−

22

26

30

kHz

350

mV

Skip−cycle level voltage on the feedback pin

−

300

mV

Skip

hysteresis

Hysteresis on the skip comparator

−

30

mV

INTERNAL SLOPE COMPENSATION

Internal ramp level @ 25

°C (Note 4)

4

2.5

V

Internal ramp resistance to CS pin

4

20

k

W

4. A 1 M

W resistor is connected from pin 4 to the ground for the measurement.

PROTECTIONS

5

24

25.5

27

V

5

20

ms

Timer

Internal auto−recovery fault timer duration

−

100

130

160

ms

Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product

performance may not be indicated by the Electrical Characteristics if operated under different conditions.