Philips Semiconductors
Product specification
CAN transceiver for 24 V systems
FEATURES
•
Fully compatible with the
“ISO 11898-24 V”
standard
•
Slope control to reduce RFI
•
Thermally protected
•
Short-circuit proof to battery and ground in 24 V
powered systems
•
Low-current standby mode
•
An unpowered node does not disturb the bus lines
•
At least 110 nodes can be connected
•
High speed (up to 1 Mbaud)
•
High immunity against electromagnetic interference.
QUICK REFERENCE DATA
SYMBOL
V
CC
I
CC
1/t
bit
V
CAN
V
diff
T
amb
PARAMETER
supply voltage
supply current
maximum transmission speed
CANH, CANL input/output voltage
differential bus voltage
ambient temperature
standby mode
non-return-to-zero
CONDITIONS
−
1
−36
1.5
−40
MIN.
4.5
GENERAL DESCRIPTION
PCA82C251
The PCA82C251 is the interface between the CAN
protocol controller and the physical bus. It is primarily
intended for applications (up to 1 Mbaud) in trucks and
buses. The device provides differential transmit capability
to the bus and differential receive capability to the CAN
controller.
MAX.
5.5
275
−
+36
3.0
+125
V
UNIT
µA
Mbaud
V
V
°C
ORDERING INFORMATION
TYPE
NUMBER
PCA82C251
PCA82C251T
PCA82C251U
PACKAGE
NAME
DIP8
SO8
−
DESCRIPTION
plastic dual in-line package; 8 leads (300 mil)
plastic small outline package; 8 leads body width 3.9 mm
bare die; 2840
×
1780
×
380
µm
CODE
SOT97-1
SOT96-1
−
2000 Jan 13
2
Philips Semiconductors
Product specification
CAN transceiver for 24 V systems
FUNCTIONAL DESCRIPTION
The PCA82C251 is the interface between the CAN
protocol controller and the physical bus. It is primarily
intended for applications up to 1 Mbaud in trucks and
buses. The device provides differential transmit capability
to the bus and differential receive capability to the CAN
controller. It is fully compatible with the
“ISO 11898-24 V”
standard.
A current limiting circuit protects the transmitter output
stage against short-circuit to positive and negative battery
voltage. Although the power dissipation is increased
during this fault condition, this feature will prevent
destruction of the transmitter output stage.
If the junction temperature exceeds a value of
approximately 160
°C,
the limiting current of both
transmitter outputs is decreased. Because the transmitter
is responsible for the major part of the power dissipation,
this will result in a reduced power dissipation and hence a
lower chip temperature. All other parts of the IC will remain
operating. The thermal protection is particularly needed
when a bus line is short-circuited.
The CANH and CANL lines are also protected against
electrical transients which may occur in an automotive
environment.
Table 1
Truth table of the CAN transceiver
V
CC
4.5 to 5.5 V
4.5 to 5.5 V
4.5 < V
CC
< 5.5 V
0 < V
CC
< 4.5 V
Notes
1. X = don’t care.
2. If another bus node is transmitting a dominant bit, then RXD is logic 0.
Table 2
Pin Rs summary
MODE
standby
slope control
high-speed
TXD
0
1 (or floating)
X
(1)
floating
CANH
HIGH
floating
floating if
V
Rs
> 0.75V
CC
floating
CANL
LOW
floating
floating if
V
Rs
> 0.75V
CC
floating
BUS STATE
dominant
recessive
floating
floating
PCA82C251
Pin 8 (Rs) allows three different modes of operation to be
selected: high-speed, slope control or standby.
For high-speed operation, the transmitter output
transistors are simply switched on and off as fast as
possible. In this mode, no measures are taken to limit the
rise and fall slope. Use of a shielded cable is
recommended to avoid RFI problems. The high-speed
mode is selected by connecting pin 8 to ground.
The slope control mode allows the use of an unshielded
twisted pair or a parallel pair of wires as bus lines.
To reduce RFI, the rise and fall slope should be limited.
The rise and fall slope can be programmed with a resistor
connected from pin 8 to ground. The slope is proportional
to the current output at pin 8.
If a HIGH level is applied to pin 8, the circuit enters a low
current standby mode. In this mode, the transmitter is
switched off and the receiver is switched to a low current.
If dominant bits are detected (differential bus voltage
>0.9 V), RXD will be switched to a LOW level.
The microcontroller should react to this condition by
switching the transceiver back to normal operation
(via pin 8). Because the receiver is slower in standby
mode, the first message will be lost at higher bit rates.
RXD
0
1
(2)
1
(2)
X
(1)
CONDITION FORCED AT PIN Rs
V
Rs
> 0.75V
CC
10
µA
<
−I
Rs
< 200
µA
V
Rs
< 0.3V
CC
RESULTING VOLTAGE OR CURRENT AT PIN Rs
−I
Rs
< 10
µA
0.4V
CC
< V
Rs
< 0.6V
CC
−I
Rs
< 500
µA
2000 Jan 13
4
Philips Semiconductors
Product specification
CAN transceiver for 24 V systems
PCA82C251
LIMITING VALUES
In accordance with the Absolute Maximum Rating System (IEC 60134); all voltages are referenced to pin 2;
positive input current.
SYMBOL
V
CC
V
n
V
6
PARAMETER
supply voltage
DC voltage at pins 1, 4, 5 and 8
DC voltage at pin 6 (CANL)
0 V < V
CC
< 5.5 V; TXD HIGH
or floating
0 V < V
CC
< 5.5 V; no time
limit; note 1
0 V < V
CC
< 5.5 V; no time
limit; note 2
V
7
V
tr
T
stg
T
amb
T
vj
V
esd
DC voltage at pin 7 (CANH)
storage temperature
ambient temperature
virtual junction temperature
electrostatic discharge voltage
note 3
note 4
note 5
Notes
1. TXD is LOW. Short-circuit protection provided for slew rates up to 5 V/µs for voltages above +30 V.
2. Short-circuit applied when TXD is HIGH, followed by TXD switched to LOW.
3. In accordance with
“IEC 60747-1”.
An alternative definition of virtual junction temperature is:
T
vj
= T
amb
+ P
d
×
R
th(vj-a)
, where R
th(vj-a)
is a fixed value to be used for the calculation of T
vj
. The rating for T
vj
limits
the allowable combinations of power dissipation (P
d
) and ambient temperature (T
amb
).
4. Classification A: human body model; C = 100 pF; R = 1500
Ω;
V =
±2500
V.
5. Classification B: machine model; C = 200 pF; R = 0
Ω;
V =
±250
V.
THERMAL CHARACTERISTICS
SYMBOL
R
th(j-a)
PCA82C251
PCA82C251T
QUALITY SPECIFICATION
According to
“SNW-FQ-611 part E”.
PARAMETER
thermal resistance from junction to ambient
CONDITIONS
in free air
100
160
K/W
K/W
VALUE
UNIT
transient voltage on pins 6 and 7 see Fig.8
CONDITIONS
MIN.
−0.3
−0.3
−36
−36
−36
MAX.
+7.0
+36
+36
+36
+36
+200
+150
+125
+150
+2500
+250
V
V
V
V
V
V
°C
°C
°C
V
V
V
CC
+ 0.3 V
UNIT
0 V < V
CC
< 5.5 V; no time limit
−36
−200
−55
−40
−40
−2500
−250
2000 Jan 13
5
Analog electronics
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