L9637D(1998) Просмотр технического описания (PDF) - STMicroelectronics
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L9637D Datasheet PDF : 11 Pages
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Figure 2: ISO Application Circuit
L9637
VS
510 Ohm
VS
40V
R KO
K
CK K
0.4 Ohm
Diagnostic
Tester
LI
L
VCC
RTX RLO RRX
5V
IK OFF
-
+
1 ,75V
-
+
-
+
ILI
TX
VCC
I/O
RX
I/O
uP
LO
I/O
GND
VDD
ECU1
K
CK
LI
ECU2
FUNCTIONAL DESCRIPTION
The L9637 is a monolithic bus driver designed to
provide bidirectional serial communication in auto-
motive diagnostic applications according to the
specification ”Diagnostic Systems ISO9141”.
The device provides a bidirectional link, called K,
to the VBat related diagnosis bus. It also includes
a separate comparator L which is also able to be
linked to the VBat bus. The input TX and output
RX of K are related to VCC with her integrated pull
up resistances. Also the L comparator output LO
has a pull up resistance connected to VCC.
The maximum external pull up resistance at K re-
lated to VS should not be higher than RKO ≤ 5KΩ
to achieve clear output ON conditions.
All VBat bus defined inputs LI and K have supply
voltage dependent thresholds together with suf-
ficent hysteresis to suppress line spikes. These
pins are protected against overvoltages, shorts to
GND and VS and can also be driven beyond VS
and GND. These features are also given for TX,
RX and LI only taking into account the behaviour
of the internal pull up resistances. The thermal
shut down function switches OFF the K output if
the chip temperature increases above the thermal
shut down threshold. To reactivate K again the
chip temperature must decrease below the K
switch ON temp. To achieve no fault for VS under-
voltage conditions the outputs will be switched
OFF and stay at high impedance. The device is
also protected against reverse battery condition.
During lack of VS or GND all pins shows high im-
pedance characteristic. To realize a lack of the VS
related bus line LI and K the outputs LO and RX
shows defined ON status.
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