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PDF LT1796 Data sheet ( Hoja de datos )
| Número de pieza | LT1796 | |
| Descripción | Overvoltage Fault Protected CAN Transceiver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT1796 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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LT1796
Overvoltage Fault Protected
CAN Transceiver
FEATURES
s Protected from Overvoltage Line Faults to ±60V
s ESD Protection to IEC-1000-4-2 Level 4
±15kV Air Gap Test
±8kV Contact Mode Test
s ISO 11898 Compatible
s High Input Impedance Supports Up to 256 Nodes
s Controlled Slew Rates for EMI Emissions Control
s High Impedance Outputs When Off or
Powered Down
s Short-Circuit Protection On All Outputs
s Thermal Shutdown Protection
s Pin Compatible with Philips PCA82C251
U
APPLICATIO S
s Industrial Control Data Networks
s Automotive Systems
s HVAC Controls
DESCRIPTIO
The LT®1796 CAN transceiver provides built-in fault toler-
ance to survive in industrial and automotive environ-
ments. Discrete protection devices are not needed. Bus
interface pins can withstand voltage faults up to ±60V with
respect to ground with no damage to the device. Faults
may occur while the transceiver is active, shut down or
powered off. On-chip ESD protection withstands up to
±15kV air discharges and ±8kV contact mode discharges
tested per IEC-1000-4-2. Loss of power or ground con-
nections does not damage the IC.
The circuit operates with data rates up to 125kbaud. A slew
control pin allows control of transmitted data pulse edges
to control EMI and reflection problems on imperfectly
terminated lines. High output current drive allows the use
of inexpensive PVC cable with impedance as low as 72Ω.
The 100kΩ input impedance allows up to 256 transceivers
per data network.
The LT1796 is available in 8-lead PDIP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Fault Protected CAN Bus Network
RT
120Ω
5V
0.1µF
1
TXD
LT1796
D
7
4
RXD
R
6
5
VREF
GND RS
28
RT
120Ω
5V
125kbps CANH and CANL Driver Output
0.1µF
CANH-CANL
2V/DIV
LT1796
7
1
D TXD
CANH
2V/DIV
CANL
2V/DIV
6
4
R RXD
5
VREF
RS
8
GND
2
1796 TA01
TXD IN
5V/DIV
5V/DIV
1796 TA02
1796f
1
1 page  
LT1796
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Thresholds vs
Temperature
0.80
Receiver Propagation Delay vs
Temperature
400
0.75
VTH RISING
0.70
VTH FALLING
0.65
350
tRXDOFF
300
tRXDON
250
0.60
–50 –25 0
25 50
TEMPERATURE (°C)
75 100
1796 G10
200
–50 –25 0 25 50
TEMPERATURE (°C)
75 100
1796 G11
PI FU CTIO S
TXD (Pin 1): Driver Input. Logic-level thresholds are set by
VREF. A logic input level higher than VREF turns the driver
outputs off, releasing control of the CANH and CANL lines.
A logic input less than VREF 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 dam-
age.
GND (Pin 2): Ground.
VCC (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. VCC 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.
VREF (Pin 5): Reference Output. The reference voltage sets
the TXD input threshold and the recessive bus common
mode voltage at CANH and CANL. VREF is approximately
VCC/2 for low voltage operation. When VCC > 7.5V, VREF
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 VCC. 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.
RS (Pin 8): Slope Control. This pin is a multifunction
control pin. When RS is high (VRS > 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 RS is
tied low through a resistance of less than 3k. The current
out of RS will be limited to about 500µA in the low state.
Controlling the current out of RS with a resistor greater
than 3k or by using a current source allows slew rate
control of the data output onto CANH and CANL.
1796f
5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LT1796.PDF ] | |
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