LT1796
6
1796fa
For more information www.linear.com/LT1796
pin FuncTions
TXD (Pin 1): Driver Input. Logic-level thresholds are set
by V
REF
. A logic input level higher than V
REF
turns the
driver outputs off, releasing control of the CANH and
CANL lines. A logic input less than V
REF
turns the driver
outputs on, pulling CANH high and CANL low. An open
TXD input will float high, turning the driver outputs off.
The TXD input pin can withstand voltages from –0.3V to
44V with no damage.
GND (Pin 2): Ground.
V
CC
(Pin 3): Positive Supply Input. Normal operation is
with a 4.75V to 5.25V supply. Operation with supplies up
to 44V is possible with unterminated bus lines. Operation
at high voltages with normally terminated busses will
result in excessive power dissipation and activation of the
thermal shutdown circuit. V
CC
should be decoupled with
a 0.1µF low ESR capacitor placed as close to the supply
pin as possible.
RXD (Pin 4): Receiver TTL Level-Logic Output. A high level
output indicates a recessive state (zero-volt differential)
bus. A dominant state forces a low receiver output.
V
REF
(Pin 5): Reference Output. The reference voltage sets
the TXD input threshold and the recessive bus common
mode voltage at CANH and CANL. V
REF
is approximately
V
CC
/2 for low voltage operation. When V
CC
> 7.5V, V
REF
maintains a 3.5V level.
CANL (Pin 6): CAN Bus Low Data Line. The CANL pin is
one input to the receiver and the low driver output. In the
dominant state (TXD low), the driver pulls the CANL pin
to within 1V of GND. In the recessive state (TXD high),
the driver output stays high impedance. The CANL pin is
protected from voltage faults from –60V to 60V in domi
-
nant, recessive, standby or powered off modes. On-chip
ESD protection meets IEC-1000-4-2 levels.
CANH
(Pin 7): CAN Bus High Data Line. The CANH pin
is one input to the receiver and the high driver output. In
the dominant state (TXD low), the driver pulls the CANH
pin to within 1V of V
CC
. In the recessive state (TXD high),
the driver output stays high impedance. The CANH pin is
protected from voltage faults from –60V to 60V in domi
-
nant, recessive, standby or powered off modes. On-chip
ESD protection meets IEC-1000-4-2 levels.
R
S
(Pin 8): Slope Control. This pin is a multifunction
control pin. When R
S
is high (V
RS
> 4V), the circuit goes
into a low power standby mode. In standby, the driver
always stays in a high impedance (recessive) state. The
receiver operates in a low power (slow) monitoring mode.
Received data may be used to “wake-up” the system to full
functionality. Full speed normal operation occurs if R
S
is
tied low through a resistance of less than 3k. The current
out of R
S
will be limited to about 500µA in the low state.
Controlling the current out of R
S
with a resistor greater
than 3k or by using a current source allows slew rate
control of the data output onto CANH and CANL.
