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L9349-LF

Quad intelligent power low side switch

STMicroelectronics 

L9349-LF

Electrical specifications

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 VOUT < 32V and thermal overload. In short

circuit condition the output will be disabled after a short delay time tDOL. The thermal disable

for TJ > 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 VOUV for OFF and IOUC for ON conditions to recognize open load

(RL  20K, RL > 38) in OFF and ON conditions.

Also the output voltages VO1- 4 are compared to each other output in OFF condition with a

fixed offset of VOUV to recognize load bypasses. The VOUV diagnoses is suppressed

during the flyback phases of the compared output. The outputs 1 and 4 are compared for

VOUV 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 VS, 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 IOOC, the output current will be limited internally during the diagnostic overload

delay switch-off time tDOL.

The device complies the ISO 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

Overloading of output

X

(also shorted load to supply)

Open load

(under voltage detection)

Open load

X

(under current detection)

Overtemperature

X

Power-signal GND-loss

X

Power-signal GND-loss

Openload difference

4s

X

-

-

4s

4s

X

4s

X

4s

Reset done by

INx = “LOW”

INx = “LOW”

INx = “LOW”

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