NCV7694
Open Load Detection
VBAT
VDD_MCU
VSTRING
DC /DC
EN
C1
NCV898031
R2
20 kW
VS
VSTR
VSTRING > VSTRth
FLASH = High
DET
FLASH
DIAG
FLASH
GATE
DIAG
NCV7694
VFB
<
150 mV
FB
R
R
ETL
FRL
R3
R1
Define
max
exposure
time
R4
Define
GND
max
frequency
Figure 5. Open Load Detection Circuit
When Open Load fault is introduced during
FLASH = High and V > V , the 22 ms blanking
time eliminate the false faults. When blanking time expires,
the NCV7694 immediately report a fault on the DIAG pin.
The output GATE pin remains active. The DIAG pin is
recovered with the falling edge on the FLASH pin or after
ETL counter is expired.
approximately 2 ms to re−activate the DC/DC V
STRING
voltage of the converter. With typical FRL setting, the driver
will be ready to perform the diagnostic on the next FLASH
pulse.
If the ENable of the DC/DC converter is not driven by
NCV7694, the Open Load is reported to the DIAG pin.
STRING
STRth
Diagnostic is not active when V
< V
. The first
STRING
STRth
If EN pin of the DC/DC converter is connected to the
DIAG output, the Open Load causes switching OFF the
FLASH pulse will not be detected when driver is going to be
recovered from a Short to GND fault because the DC/DC
converter in not fully active.
V
STRING
voltage. The DIAG pin is recovered as soon as
FLASH pin goes low or ELT counter expired. It will take
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