NCP1249A, NCP1249B

http://onsemi.com

6

Table 4. ELECTRICAL CHARACTERISTICS

Symbol

Unit

Max

Typ

Min

Pin

Rating

REMOTE SECTION

Remote pin voltage below which is the off−mode deactivated

2

1

1.5

2

V

Remote pin voltage above which is the off−mode activated

2

7.2

8

8.8

V

REM_Timer

Remote timer duration

2

70

−

140

ms

Internal remote pull down switch resistance

2

1000

−

3000

W

2

−

0.02

1

mA

FEEDBACK SECTION

Internal pull−up resistor

3

17

kW

Equivalent ac resistor from FB to gnd

3

10

15

20

kW

Pin 3 to current setpoint division ratio

3,4

4

−

Feedback voltage below which the peak current is frozen

3

1

V

FREQUENCY FOLDBACK

Frequency foldback level on the feedback pin –

≈47% of maximum peak current

3

1.9

V

Transition frequency below which skip−cycle occurs

−

22

26

30

kHz

3

1.5

V

Skip−cycle level voltage on the feedback pin

3

400

mV

Skip hysteresis

Hysteresis on the skip comparator – note 1

3

30

mV

INTERNAL SLOPE COMPENSATION

Internal ramp level @ 25°C – note 3

4

2.5

V

Internal ramp resistance to CS pin

4

20

kW

PROTECTIONS

Latching level input

5

2.7

3

3.3

V

Blanking time after drive turn off

5

1

ms

Number of clock cycles before latch confirmation

−

4

−

OVP detection time constant

5

600

ns

Feedback voltage at which an overload is considered –

OPP pin is grounded

3

3.2

V

Feedback voltage above which a short−circuit is considered

3

3.9

4.1

4.3

V

−

100

200

300

ms

−

25

50

75

ms

8

26

27.5

29

V

8

20

30

ms

Auto−recovery timer duration

−

0.7

−

−

s

TEMPERATURE SHUTDOWN

−

150

°C

Temperature shutdown hysteresis

−

30

°C

2. Guaranteed by design

3. See characterization table for linearity over negative bias voltage – we recommend keeping the level on pin 5 below −300 mV.

4. A 1−MW resistor is connected from pin 4 to the ground for the measurement.