Datasheet

RUW15 Series
Isolated Ultra-Wide Input DC/DC Converters
KDC_RUW15.B02 Page 4 of 13
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APPLICATION NOTES (continued)
Power Fail Warning Details
A ‘power fail’ signal is available which goes active after the input voltage drops out but before the output loses regulation. Over-temperature and over-voltage monitoring is
included which also activates the ‘power fail’ signal.The signal goes active if the output voltage exceeds approximately 15 % of nominal, if the output is grossly less than
nominal such as under short circuit conditions or if the case temperature exceeds approximately 120 degrees C. The signal is an open pnp emitter output which goes to a
low voltage, typically less than 1V when active, signifying a fault. The signal goes active some milliseconds before the output drops after the converter input drops to zero,
effectively giving a power fail warning.
The actual value of warning time is defined by the hold-up capacitance added as shown below. The signal can sink 50 mA and withstand 30 V in the inactive condition. The
signal is referenced to RUW15 -Vout and typically is pulled to a system rail with a 10K resistor. The open emitter arrangement allows the RUW15 to actively sink current into
the Power Fail output even if the RUW15 is unpowered or short circuited, correctly indicating a fault condition.
Power Fail Warning Graphs
RUW15SL12HC RUW15SL24HC
RUW15SL05HC
RUW15SL24HC
0
1
2
3
4
5
6
50 100 150 200 250 300 350 400 450 500
Advance Power Fail time (ms)
Capacitance uF
Power Fail minimum
0
1
2
3
4
5
6
50 100 150 200 250 300 350 400 450 500
Advance Power Fail time (ms)
Capacitance uF
Power Fail minimum ms.
0
1
2
3
4
5
6
0 50 100 150 200 250 300 350 400 450 500
Advance Power Fail time (ms)
Capacitance uF
Power Fail minimum ms.