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SCY99080CDWR2G

High Performance Switch-Mode Power Supply Controller for Backlight and LLC Converters

ON Semiconductor 

OTP_latch

NTC

DDA002C

VDD

SS_OK

OTPref_I = 170 mA

OTPref _V = 1.5 V

50 ms

Noise

Filter

to permanent

latch

Figure 51. Internal Connection of the OTP Latch

OTP Latch

For most of the consumer electronic products there is a

necessity to implement over temperature protection to

comply with international standards. The DDA002C

controller features special OTP Latch input that makes OTP

implementation very easy and cheap since it does not require

any active components. Connection of the OTP Latch can be

seen in Figure 51.

The OTP_latch input permanently latches off the

controller if the external NTC resistor resistance decreases

below 8.8 kΩ (1.5 V). The temperature turn off threshold can

be accurately adjusted using a serial or parallel resistor

connected to the given NTC sensor. The OTP_latch input

includes a 50 ms filter that improves noise immunity. Note

that the OTP_latch input is ignored during the whole startup

sequence (i.e. PFC delay, preheat and soft−start). When the

latch is once asserted, the VCC of the controller has to be

decreased below the VCC(min) level or the BO comparator

has to be re−triggered in order to restart the controller.

Figure 54 shows typical operating waveforms of the

OPT_latch input.

EN1 Input

The enable 1 input offers a way to permanently latch off

the controller in case the critical operating conditions of the

application are reached − such as over current or over

voltage conditions. Since this is the latching input it includes

50 ms noise filter to overcome false triggering caused by the

switching noise (pure grounding etc.). Internal connection

of the EN1 comparator is depicted in Figure 52. Note that the

enable 1 input functionality is disabled until preheat period

ends.

To Input Current

Sensing Circuitry

CIG_END

R1

EN1

R2

VEN1 = 1 V

50 ms

Noise

Filter

To Permanent Latch

Figure 52. Internal Connection of the EN1 Comparator

The Enable 1 comparator features −50 mV hysteresis,

which means that the EN1 input voltage has to go 50 mV

below VEN1 reference voltage to allow the controller to

restart. The controller can be restarted by two different

events: 1st The VCC is cycled down and up through the

VCC(off) level, or 2nd, the BO input is re−triggered (i.e. bulk

voltage is cycled down and up). Full start up sequence (PFC

delay, preheat and soft−start) occurs when the controller

restarts from EN1 latching event. Figure 53 shows the EN1

input related waveforms.

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