LT1796
Overvoltage Fault Protected
CAN Transceiver
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
Protected from Overvoltage Line Faults to
±60V
ESD Protection to IEC-1000-4-2 Level 4
±15kV
Air Gap Test
±8kV
Contact Mode Test
ISO 11898 Compatible
High Input Impedance Supports Up to 256 Nodes
Controlled Slew Rates for EMI Emissions Control
High Impedance Outputs When Off or
Powered Down
Short-Circuit Protection On All Outputs
Thermal Shutdown Protection
Pin Compatible with Philips PCA82C251
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.
APPLICATIO S
s
s
s
Industrial Control Data Networks
Automotive Systems
HVAC Controls
TYPICAL APPLICATIO
R
T
120Ω
5V
0.1µF
Fault Protected CAN Bus Network
R
T
120Ω
5V
0.1µF
125kbps CANH and CANL Driver Output
CANH-CANL
2V/DIV
LT1796
7
TXD
1
D
6
RXD
4
R
V
REF
GND
2
R
S
8
5
5
6
7
LT1796
D
1
TXD
CANH
2V/DIV
CANL
2V/DIV
TXD IN
5V/DIV
5V/DIV
1796 TA02
R
V
REF
R
S
8
GND
2
4
RXD
1796 TA01
U
1796f
U
U
1
LT1796
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
TXD 1
D
GND 2
V
CC
3
RXD 4
R
7
6
5
8
R
S
CANH
CANL
V
REF
Supply Voltage (V
CC
) .............................................. 44V
R
S
Slope Control Input Voltage ................ – 0.3V to 44V
V
REF
Reference Output Pin ......................... – 0.3V to 7V
Driver Input Voltage .................................. – 0.3V to 44V
CANH, CANL Data Line Pins ...................... – 80V to 80V
Receiver Output Voltages ............................– 0.3V to 7V
Operating Temperature Range
LT1796C .................................................. 0°C to 70°C
LT1796I .............................................. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
LT1796CN8
LT1796CS8
LT1796IN8
LT1796IS8
S8 PART MARKING
1796
1796I
N8 PACKAGE
S8 PACKAGE
8-LEAD PDIP 8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 130°C/W (N8)
T
JMAX
= 150°C,
θ
JA
= 150°C/W (S8)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
CANH
V
CANL
V
OD
PARAMETER
CANH Output Voltage
CANL Output Voltage
Dominant State Differential Output Voltage
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 4.75V to 5.25V, V
RS
= 0V unless otherwise noted.
CONDITIONS
V
TXD
= 0V, No Load
V
TXD
= 0V, R
L
= 60Ω
V
TXD
= 0V, No Load
V
TXD
= 0V, R
L
= 60Ω
V
TXD
= 0V, No Load, V
CC
= 4.75V
V
TXD
= 0V, R
L
= 60Ω, V
CC
= 4.75V
V
TXD
= 0V, R
L
= 36Ω, V
CC
= 4.75V
V
TXD
= 5V, R
L
= 60Ω
V
TXD
= 5V, R
L
= 60Ω, V
CC
= 5V
R
L
= 60Ω, V
CC
= 5V
q
q
q
q
q
q
q
q
q
q
q
q
MIN
3.8
2.8
0
0
3.0
1.5
1.2
– 10
2.7
2
2.8
TYP
4.4
3.5
0.5
1.3
3.6
2.0
1.7
0
3
2.5
MAX
5.0
4.6
0.9
1.6
5.0
4.2
4.2
10
3.5
3
2
UNITS
V
V
V
V
V
V
V
mV
V
V
V
V
µA
mA
mA
mA
mA
mA
mA
mA
mA
kΩ
kΩ
mA
mA
mA
V
REC
V
CMR
V
CMD
V
IH
V
IL
I
IN1
I
SCH
Recessive State Differential Output Voltage
Recessive State Common Mode Output Voltage
Dominant State Common Mode Output Voltage
TXD Input High Voltage
TXD Input Low Voltage
TXD Input Current
CANH Short-Circuit Current, Dominant Mode
0 < V
TXD
< V
CC
V
CANH
= 0V, V
CC
= 5.25V
V
CANH
= – 36V, V
CC
= 5.25V
V
CANH
= – 60V, V
CC
= 5.25V
V
CANH
= 60V, V
CC
= 5.25V
V
CANL
= 5V, V
TXD
= 0V, V
CC
= 5.25V
V
CANL
= 36V, V
TXD
= 0V, V
CC
= 5.25V
V
CANL
= 60V, V
TXD
= 0V, V
CC
= 5.25V
V
CANL
= – 60V, V
TXD
= 0V, V
CC
= 5.25V
V
TXD
= 5V, – 7V < V
CANH
, V
CANL
< 12V
V
TXD
= 5V, – 7V < V
CANH
, V
CANL
< 12V
V
RS
= 5V, – 60V < V
CANH
, V
CANL
< 60V
V
TXD
= 5V, – 60V < V
CANH
, V
CANL
< 60V
V
CC
= 0V, – 60V < V
CANH
, V
CANL
< 60V
q
q
q
q
q
q
q
q
q
q
q
q
q
q
–5
– 250
– 10
– 10
0
60
0
0
– 10
140
70
–3
–3
–3
–1
–1
1
1
1
–1
240
120
5
– 60
0
0
10
250
10
10
0
350
175
3
3
3
I
SCL
CANL Short-Circuit Current, Dominant Mode
R
IND
Differential Input Resistance
CANH, CANL Input Resistance
Input Fault Current (CANH, CANL)
2
U
W
U
U
W W
W
1796f
LT1796
DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
TH
∆V
TH
V
OH
V
OL
I
SCR
V
REF
V
REFSC
V
RSSB
I
RS
PARAMETER
Differential Input Threshold Voltage
for Receiver
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
Receiver Short-Circuit Current
Reference Output Voltage
Reference Output Short-Circuit Current
R
S
Pin Standby Threshold
R
S
Input Current
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 4.75V to 5.25V, V
RS
= 0V unless otherwise noted.
CONDITIONS
V
RS
= 0V, – 7V < V
CM
< 12V
V
RS
= 5V, – 7V < V
CM
< 12V
– 7V < V
CM
< 12V
V
CC
= 4.75V, I
O
= – 400µA, V
ID
= 500mV
V
CC
= 4.75V, I
O
= 1.6mA, V
ID
= 900mV
0V < V
O
< V
CC
, V
CC
= 5.25V
– 100µA < I
REF
< 100µA
0 < V
REF
< V
CC
V
CC
= 5V
V
RS
= 5V, V
CC
= 5V
V
RS
= 0V, V
CC
= 5V
R
S
= 47k, V
CC
= 5V
Dominant
Recessive
Standby
No Load, V
RS
= 0V, V
TXD
= 0V, V
CC
= 5.25V
R
L
= 60Ω, V
RS
= 0V, V
TXD
= 5V, V
CC
= 5.25V
R
L
= 60Ω, V
RS
= 5V, V
CC
= 5.25V
q
q
q
q
q
q
q
q
q
q
q
q
q
q
MIN
0.5
0.5
TYP
MAX
0.9
0.9
UNITS
V
V
mV
V
70
3
7
2.25
– 20
2.5
– 270
– 90
2.8
0.1
– 200
– 60
4.3
3.8
0.8
3.6
0.15
20
2.5
0.4
85
2.7
20
4
10
– 140
– 40
7
7
1.5
V
mA
V
mA
V
µA
µA
µA
mA
mA
mA
I
CC
Supply Current
SWITCHI G CHARACTERISTICS
SYMBOL
t
BIT
F
MAX
t
TXDON
t
TXDOFF
t
LBON
t
LBOFF
t
RXDOFF
t
RXDON
t
RXDOFFSB
t
RXDONSB
t
WAKE
SR
+
SR
–
PARAMETER
Minimum Bit Time
Maximum Data Rate
Driver Input to Bus Active
Driver Input to Bus Inactive
Loopback Delay Active
Loopback Delay Inactive
Receiver Delay Off
Receiver Delay On
Receiver Delay Off, Standby
Receiver Delay On, Standby
Wake-Up Delay from Standby
Positive Slew Rate
Negative Slew Rate
The
q
denotes the specifications which apply over the full operating
temperature range. V
RS
= 0V unless otherwise noted. (Note 2)
CONDITIONS
(Note 3)
(Note 3)
Figures 1, 2
Figures 1, 2
Figures 1, 3
Figures 1, 3
Figures 1, 4
Figures 1, 4
V
RS
= 4V, Figures 1, 4
V
RS
= 4V, Figures 1, 4
Figures 1, 5
R
S
= 0k
R
S
= 47k
R
S
= 0k
R
S
= 47k
R
S
= 0k
R
S
= 47k
R
S
= 0k
R
S
= 47k
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
Unless otherwise specified, testing done at V
CC
= 5V, T
A
= 25°C.
U
MIN
125
TYP
MAX
8
UNITS
µs
kbps
ns
ns
ns
ns
µs
µs
ns
ns
µs
µs
µs
V/µs
V/µs
V/µs
V/µs
300
350
500
600
0.6
1.5
400
300
1.5
1
1
5
2
5
2
12
7
36
5
500
1000
1000
1500
1.5
3
600
600
4
4
15
65
30
65
15
Note 3:
Bit time and data rate specifications are guaranteed by driver and
receiver delay time measurements.
1796f
3
LT1796
TYPICAL PERFOR A CE CHARACTERISTICS
Dominant State Bus Voltage
vs R
L
3.0
T
A
= 25° C
2.5
2.0
V
OD
(V)
SUPPLY CURRENT (mA)
1.5
1.0
0.5
0
0
50
R
S
Pin Current vs R
S
250
T
A
= 25° C
SLEW CONTROL CURRENT (µA)
200
150
SR
+
(V/µs)
SR
–
(V/µs)
100
50
0
0
20
40
R
S
(kΩ)
60
80
1796 G04
Transmitter Propagation Delay vs
Temperature
700
600
t
TXDOFF
AND t
TXDON
(ns)
500
t
TXDOFF
300
200
100
0
–50
t
TXDON
I
SC
(mA)
–40
–60
–80
I
SC
(mA)
400
–25
0
25
50
TEMPERATURE (°C)
4
U W
75
1796 G07
Supply Current vs Data Rate
Transmitting, 50% Duty Cycle
24
T
A
= 25° C
23
22
21
20
100
150
R
L
(Ω)
200
250
1796 G01
0
50
150
100
DATA RATE (Kbps)
200
250
1796 G03
Positive Slew Rate vs R
S
15
T
A
= 25° C
30
40
Negative Slew Rate vs R
S
T
A
= 25° C
10
20
5
10
0
0
0
20
40
R
S
(kΩ)
60
80
1796 G05
0
20
40
R
S
(kΩ)
60
80
1796 G06
CANH Short-Circuit Current vs
Voltage
20
T
A
= 25° C
0
–20
90
80
70
60
50
40
30
20
10
CANL Short-Circuit Current vs
Voltage
T
A
= 25° C
–100
–120
–60
0
100
–40
–20
0
V
CANH
(V)
20
40
60
1796 G08
–10
–60
–40
–20
0
20
V
CANL
(V)
40
60
1796 G09
1796f
LT1796
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Thresholds vs
Temperature
0.80
0.75
V
TH
RISING
t
RXDOFF
AND t
RXDON
(ns)
V
TH
(V)
0.70
V
TH
FALLING
0.65
0.60
–50
–25
PI FU CTIO S
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 dam-
age.
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.
1796f
U W
Receiver Propagation Delay vs
Temperature
400
350
t
RXDOFF
300
t
RXDON
250
0
25
50
TEMPERATURE (°C)
75
100
1796 G10
200
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1796 G11
U
U
U
5
嵌入式系统
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