l9637 STMicroelectronics, l9637 Datasheet - Page 5

• Manufacturer Part Number: l9637
• Description: Iso 9141 Interface
• Manufacturer: STMicroelectronics

Figure 2: ISO Application Circuit
FUNCTIONAL DESCRIPTION
The L9637D is a monolithic bus driver designed
to provide bidirectional serial communication in
automotive diagnostic applications according to
the specification "Diagnostic Systems ISO9141".
The device provides a bidirectional link, called K,
to the V
a separate comparator L which is also able to be
linked to the V
RX of K are related to V
up resistances. Also the L comparator output LO
has a pull up resistance connected to V
The maximum external pull up resistance at K re-
lated to V
to achieve clear output ON conditions.
All V
voltage dependent thresholds together with suf-
0.4 Ohm
510 Ohm
Bat
VS
Bat
bus defined inputs LI and K have supply
S
related diagnosis bus. It also includes
should not be higher than R
Diagnostic
Tester
Bat
bus. The input TX and output
K
L
CC
with her integrated pull
40V
R KO
C K
VS
LI
C K
K
LI
K
ECU2
ECU1
CC
KO
.
5K
IK OFF
ILI
ficent hysteresis to suppress line spikes. These
pins are protected against overvoltages, shorts to
GND and V
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 V
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 V
pedance characteristic. To realize a lack of the V
related bus line LI and K the outputs LO and RX
shows defined ON status.
+
+
-
-
S
and can also be driven beyond V
+
-
RTX
S
or GND all pins shows high im-
1,75V
RLO
RRX
VCC
TX
RX
LO
GND
I/O
I/O
I/O
L9637D
S
under-
VDD
VCC
u P
5V
5/10
S
S