NCP1237 datasheet(6/34 Pages) ONSEMI

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NCP1237

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ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°C, VHV = 120 V,

VCC = 11 V unless otherwise noted)

Characteristics

Unit

Max

Typ

Min

Symbol

Test Condition

CURRENT SENSE

Input Bias Current

VCS = 0.7 V

Ibias

−

0.02

−

Maximum internal current setpoint

VFB > 3.5 V

VILIM

0.665

0.7

0.735

Threshold for immediate fault protection activation

VCS(stop)

0.95

1.05

1.15

Propagation delay from VILIM detection to DRV off

VCS = VILIM

tdelay

110

Leading Edge Blanking Duration for VILIM

tLEB

190

250

310

Leading Edge Blanking Duration for VCS(stop)

tBCS

120

150

Slope of the compensation ramp

Scomp(65kHz)

−

−32.5

−

mV / ms

Soft−start duration

From 1st pulse to

VCS = VILIM

tSSTART

2.8

4.0

5.2

OVERPOWER COMPENSATION

VHV to IOPC conversion ratio

KOPC

−

0.5

−

mA / V

Current flowing out of CS pin

VHV = 125 V

VHV = 162 V

VHV = 325 V

VHV = VHV(OV2) − 5 V

IOPC(125)

IOPC(162)

IOPC(325)

IOPC(max)

−

102

104

120

−

138

FB voltage above which IOPC is applied

VFB(OPC)

1.50

1.65

1.80

FB voltage below which IOPC = 0

VFB(OPCE)

−

1.25

−

Refresh operation for dc operation

tWD

FEEDBACK

Internal pull−up resistor

TJ = 25°C

RFB(up)

VFB to internal current setpoint division ratio

KFB

4.7

5.0

5.3

−

Internal pull−up voltage on the FB pin

VFB(ref)

4.3

5.0

5.7

OVERCURRENT PROTECTION

Fault timer duration

From CS reaching VILIMIT to

DRV stop

tfault

Autorecovery mode latch−off time duration

tautorec

1.0

1.4

1.8

CS threshold for transient peak timer activation

VCS(tran)

0.47

0.5

0.53

Transient peak power timer duration

VCS(peak) = VILIM – 5%

From 1st time VCS >

VCS(tran) to DRV stop

ttran

117

156

195

FREQUENCY FOLDBACK

Feedback voltage threshold below which frequency

foldback starts

VFB(fold)

1.3

1.4

1.5

Minimum switching frequency

VFB = Vskip(in) + 0.2 V

fOSC(min)

kHz

Threshold below which the frequency foldback is

finished and the controller switches at fOSC(min)

VFB(endfold)

−

1.0

−

SKIP CYCLE MODE

Feedback voltage thresholds for skip mode

VFB going down

VFB going up

Vskip(in)

Vskip(out)

0.63

0.72

0.7

0.80

0.77

0.88

Soft−skip duration

From 1st pulse to VCS =

VFB(fold) / KFB

tSSKIP

−

100

−

6. Internal supply current only, current in FB pin not included (current flowing through GND pin only).

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