NCP1253

http://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

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

kW

Equivalent ac resistor from FB to GND

2

16

kW

Pin 2 to current setpoint division ratio

−

4.2

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

kW

4. A 1 MW 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