CIRCUIT DESCRIPTION

The L9377 is a dual low side driver for inductive

loads like valves in automotive environment. The

device is enabled by a common CMOS compat-

ible ENABLE high signal. The internal pull down

current sources at the ENABLE and INPUT pins

protect the device in open input conditions

against malfunctions. An output slope limitation

for du/dt is implemented to reduce the EMI. An in-

tegrated active flyback voltage limitation clamps

the output voltage during the flyback phase to

50V.

Each driver is protected against short circuit and

thermal overload. In short circuit condition the

output will be disabled after a short delay time

until a negative slope occure at the correspondent

the output will be reseted if the junction tempera-

ture decreases about 20°C below the disable

threshold temperature.

For the real time error diagnosis the voltage and

the current of the outputs are compared with in-

> 38

Ω) in ON and OFF conditions. The diagnostic

operates also in the extended supply voltage

range of 4.5V

≤ VS ≤ 32V.

against each other in OFF condition with a fixed

offset of

To suppress mail

∆VO diagnoses during the fly-

back phases of the compared output, the

∆VO di-

agnostic includes a latch function. Reaching the

nal is reseted by a latch. To activate again this

kind of diagnostic a low signal at the correspon-

dent INPUT or the ENABLE pin must occur (see

also Fig.3).

The diagnostic output level in connection with dif-

ferent ENABLE and INPUT conditions allows to

recognize different fail states, like overtemp, short

to VSS, short to GND, bypass to GND and

dis-

connected load (see also page 7 diagnostic ta-

ble).

The diagnostic output is also protected against

ternally during the diagnostic overload delay

OUT1

OUT2

VS

Z VALVE

Z VALVE

V Batt

Channel 1

Channel 2

Output

Control

Overtemp

R

QS

Delay

Timer

Overload

Openload

GND

DIAG2

IN2

EN

DIAG1

IN1

Controller

+5V

R O

Diagnostic

Control

µ P

Figure 5: Application circuit diagram.

L9377

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