NCV7694
Short to VS
VBAT
VDD_MCU
DC / DC
VSTRING
EN
NCV898031
C1
R2
20 kW
VS
VSTRING > VSTRth
VSTR
FLASH = High
V
DET > (VSTRING– 1.22)V
FLASH
FLASH
DET
High
transistor
current
GATE
DIAG
DIAG
RETL
NCV7694
GATE − OFF
FB
R3
R1
Define
max
RFRL
exposure
time
R4
GND
Define
max
frequency
Figure 9. Short to VSTRING Detection Circuit
When Short Cathode of the LEDs to V
introduced during the FLASH
voltage is
High and
connected to the Enable of the DC/DC converter. The fault
is latched during the FLASH signal is high or until ETL
counter expires. The device will be recovered only with next
falling edge on the FLASH or when the ETL counter is
expired.
STRING
=
V
STRING
> V
, the 10 ms blanking time eliminate the
STRth
false faults. When the blanking time expires, the NCV7694
immediately switch OFF the GATE output to protect the
external transistor against high power dissipation. The
DIAG pin will report a fault which will lead to switching
The diagnostic is not active when V
also during FLASH = Low.
< V
or
STRING
STRth
OFF the DC/DC V
voltage if the DIAG pin is
STRING
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