L9349-LF Electrical specifications
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3.6 Circuit description
The L9349 is a quad low side driver for inductive loads like valves in automotive
environment. The internal pull down current sources at the ENable and INput pins assure in
case of open input conditions that the device is switched off. An output voltage slope
limitation for du/dt is implemented to reduce the EMI. An integrated active flyback voltage
limitation clamps the output voltage during the flyback phase to 50 V.
Each driver is protected against short circuit at V
OUT
< 32V and thermal overload. In short
circuit condition the output will be disabled after a short delay time t
DOL
. The thermal disable
for T
J
> 180°C of the output will be reset if the junction temperature decreases about 20°C
below the disable threshold temperature.
The overtemperature, overload and groundloss information is stored until IN is low.
For the real time error diagnosis the voltage and the current of the outputs are compared
with internal fixed values V
OUV
for OFF and I
OUC
for ON conditions to recognize open load
(R
L
20K, R
L
> 38) in OFF and ON conditions.
Also the output voltages V
O1- 4
are compared to each other output in OFF condition with a
fixed offset of
V
OUV
to recognize load bypasses. The V
OUV
diagnoses is suppressed
during the flyback phases of the compared output. The outputs 1 and 4 are compared for
V
OUV
and also outputs 2 and 3 are compared.
The diagnostic output level in connection with different ENable and INput conditions allows
to recognize different fail states, like overtemp, short to V
S
, short to GND, bypass to GND
and disconnected load (see Table 7: Diagnostic).
The diagnostic output is protected against short circuit. Exceeding the over load current
threshold I
OOC
, the output current will be limited internally during the diagnostic overload
delay switch-off time t
DOL
.
The device complies the I
SO
pulses imposed to the supply voltage of the valves without any
failures of the functionality. Therefore some diagnostic functions are internal filtered. The
following table shows the corresponding filter time for each detected signal.
Table 8. Corresponding filter time for each detected signal
ON State
EN and IN =
HIGH
OFF State
EN or IN,
= LOW
min.
Filter
time
Reset done by
Overloading of output
(also shorted load to supply)
X4
sINx = “LOW”
Open load
(under voltage detection)
X-
Open load
(under current detection)
X-
Overtemperature X 4
sINx = “LOW”
Power-signal GND-loss X 4
sINx = “LOW”
Power-signal GND-loss X 4
s
Openload difference X 4
s
