NCV7680 Datasheet, PDF (19/20 Pages) ON Semiconductor – Linear Current Regulator and Controller for Automotive LED Rear Combination Lamps

NCV7680
Latch−Off on Open String Detection
Some LED lighting systems require the complete lighting
system to shut down when the output intensity has
diminished. This eliminates a slow degradation of output
illumination. Figure 28 provides one solution for this
requirement. The open circuit fault information provided on
TAIL Input _MRA4003T3G
STOP Input _MRA4003T3G
C1
0.1uF
NTD2955
R3
C2
1k _0.22uF
C3
100nF
the DIAG pin coupled with external discrete transistors
provides the feedback needed to the FB pin to turn off the
ballast transistor drive removing the LED anode string from
any power source. This condition is held until the input
signal is toggled.
V_STRING
MRA4003T3G
R1
10k
C4
10nF
R10
R11
10k
10k
MUN2211
R9
499
R2
4.99k
R4, 3.09k
R5, 2.21k
C6
0.1uF
NCV7680
OUT1
OUT2
VP
Ballast Drive
OUT3
OUT4
FB
GND
STOP
OUT5
DIAG
OUT6
RSTOP
OUT7
RTAIL
OUT8
Note: Latch−off will be implemented under all conditions which cause DIAG to go high.
Reference the pin function description table for a summary of DIAG performance.
Figure 28. Latch−Off Circuit
R6
8.87K
V_ref
R7
1K
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