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Upgrading Note
PCA82C250/251 Í TJA1040, TJA1050
V1.0
*#+64
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Upgrading Note V1_2.doc
CAN High-Speed
PCA82C250, TJA1050, TJA1040
Upgrading
&CVGVJQH0QXGODGT
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From a functional point of view the TJA1040 is the direct successor of the PCA82C250/251. Both
transceivers provide a Standby Mode with remote wake-up capability via the bus. However, the standby
current of the TJA1040 (max. 15µA) has been significantly reduced compared to the C250/251 (max.
170µA). Due to functional and pinning compatibility the C250/251 can be easily replaced with the
TJA1040 within existing applications. The TJA1050 is similar to the TJA1040, but it does not offer a
dedicated Standby Mode. Thus, for applications not requiring a Standby Mode, the TJA1050 is the first
choice when replacing the C250/251.
The C250/251, TJA1050 and TJA1040 (also TJA1041) are compliant to ISO11898. This ensures
interoperability between the transceivers, allowing a gradually migration from the C250/251 to the
TJA1050 or TJA1040.
This report describes all items to be taken into account, when an existing application using the C250/251
should be upgraded towards the TJA1050 or TJA1040.
4GXKUKQP*KUVQT[
Version
Remarks
V1.0
Initial version
© 2001 Royal Philips Electronics
All rights are reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner.
The information presented in this document does not form part of any quotation or contract, is believed to be accurate and
reliable and may be changed without notice. No liability will be accepted by the publisher for any consequence of its use.
Publication thereof does not convey nor imply any license under patent- or other industrial or intellectual property rights.
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The TJA1040, like the TJA1050 and C250/251, is an ISO11898 compliant CAN High-Speed transceiver
for use in automotive and industrial applications.
The TJA1050 is designed to offer the latest achievements in terms of EMC. It is processed in the advanced
Silicon-on-Insulator (SOI) technology. As a result the TJA1050 shows an improvement of about 20dB in
emission compared to the C250/251 (using split termination). The TJA1050 mainly focuses on typical
"clamp-15" applications, which are left un-powered during ignition-off. Accordingly, the TJA1050 does
not provide a Standby Mode. Special attention was paid on achieving passive behaviour in un-powered
condition.
The TJA1040 bases on the design of the TJA1050. Employing the same SOI technology the TJA1040
shows the same excellent EMC performance as the TJA1050. The main difference is that the TJA1040
provides a Standby Mode with remote wake-up capability via the bus as known from the C250/251. Thus,
the TJA1040 can be regarded as the functional successor of the C250/251. Moreover, the TJA1040 is
compatible to the C250/251 with both transceivers featuring the same pinning and functionality. This
allows easy replacing of the C250/251 by the TJA1040. Especially the TJA1040 offers for the first time
ideal passive behaviour when un-powered.
The TJA1040 has several advantages compared to the C250/251:
-
Completely passive to the bus if un-powered (not visible to the bus if Vcc is off)
-
Very low current consumption in Standby Mode (max. 15µA)
-
Improved electromagnetic emission (EME) performance
-
Improved electromagnetic immunity (EMI) performance
-
"SPLIT" pin (replacing "Vref" pin) for effective DC stabilization of the bus
The TJA1040 is designed to be downward compatible to the C250/251 and can be used in most existent
C250/251 applications without any changes in hardware and software. The following chapters discuss all
issues concerning the migration from the C250/251 to the TJA1040 or TJA1050.
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Table 2.1 lists the main differences between the C250/251, TJA1050 and TJA1040 from an application
point of view.
Feature
PCA82C250
PCA82C251
TJA1050
TJA1040
4.5-5.5V
4.5-5.5V
4.75-5.25V
4.75-5.25V
-8V … +18V
-36V … +36V
-27V … +40V
-27V … +40V
Loop Delay (TXD→RXD)
(dom.→ rec.)
(Rs=0) 190ns
(Rs=24k) 320ns
(Rs=0) 190ns
250ns
255ns
Standby Mode with remote
wake-up
< 170µA
< 275µA
Not supported
< 15µA
Slope Control
Variable
Variable
EMC optimized
EMC optimized
< 1mA
(VCANH/L=7V)
< 2mA
(VCANH/L=7V)
< 250µA
(VCANH/L=5V)
0µA
(VCANH/L=5V)
No
No
No
Yes
Supply voltage range
Max. DC voltage at Bus
pins (6,7)
Passive behaviour if un-powered
(Leakage current of bus pins for Vcc=0V)
DC Stabilization of common mode
voltage
Table 2.1: Main differences between C250/251, TJA1050, TJA1040 ([1] [2] [3] [4])
2+00+0)
Figure 3.1 shows the pinning of the C250/251, TJA1050 and TJA1040. Apart from renaming two pins
the pinning of the three transceivers is identical.
TXD
1
GND
2
Vcc
3
RXD
4
C250/
251
8
Rs
TXD
1
7
CANH
GND
2
6
CANL
Vcc
5
Vref
RXD
8
S
TXD
1
7
CANH
GND
2
3
6
CANL
Vcc
4
5
Vref
RXD
TJA1050
8
STB
7
CANH
3
6
CANL
4
5
SPLIT
TJA1040
Figure 3.1: Pinning of the C250/251, TJA1050 and TJA1040
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Pin 8 of the transceiver is used to control the operation mode. Its symbol is "STB" for the TJA1040
referring to the Standby Mode, "Rs" for the C250/251 referring to the slope control resistor and "S" for
the TJA1050 referring to the Silent Mode. Although there are different symbols, the mode control is the
same, that means the Normal or Highspeed Mode is selected with a LOW signal at pin 8. Applying a
HIGH signal the transceivers would enter its Standby (C250/251, TJA1040) or Silent Mode (TJA1050).
8QNVCIG4GHGTGPEG2KP
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Pin 5 of the transceivers provides an output voltage of Vcc/2. In case of the C250/251 and TJA1050 the
pin 5 is attributed the symbol "Vref". The purpose of the pin "Vref" was to provide a voltage reference for
former analog comparators within CAN-controller to properly read the bit values on the bus. Nowadays a
CAN-controller usually has a digital input for the RXD signal and the pin "Vref" has become obsolete.
In case of the TJA1040 the pin 5 is attributed the symbol "SPLIT". The function of the pin is to provide a
voltage source of Vcc/2. The relatively low impedance (typ. 600Ω) of the source allows stabilizing the
common mode voltage to nominal Vcc/2. For that purpose the pin "SPLIT" should be connected to the
center tap of the split termination. This way the common mode voltage can be maintained to nearly
nominal Vcc/2 even if there are significant leakage currents flowing from the bus to GND due to possibly
unpowered nodes.
12'4#6+10/1&'5
As mentioned before the operation mode of the transceivers is controlled via the pin 8. Table 4.1 gives an
overview of the operation modes along with the provided features and the corresponding settings on pin 8.
Operation
Mode
Provided Features of
Operation Mode
Signal level at Pin 8
TJA1040
C250/251
TJA1050
LOW
LOW or
unconnected
LOW or
unconnected
Normal
(Highspeed)
- Transmit capability
- Receive capability
Standby
- Reduced current
- remote wake-up
- "Babbling Idiot" protection
HIGH or
unconnected
HIGH
Not
implemented
Slope Control
- variable slope
Not needed
GND via
10k<Rs<180k
Not needed
Silent
- "Babbling Idiot" protection
- "Receive-Only" behaviour
Not
implemented
Not
implemented
HIGH
Table 4.1: Operation Modes with their corresponding settings on pin 8
Following chapters give a short description of the different operation modes along with their provided
functionality. It turns out that the TJA1040 essentially provides the same functionality as the C250/251.
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Due to the excellent CAN signal symmetry both the TJA1050 and TJA1040 do not need a dedicated
Slope Control Mode.
0QTOCN*KIJURGGF/QFG
The Normal (Highspeed) Mode is the same for all transceivers considered here. It is used for normal CAN
communication. The digital bit stream, input at TXD, is transferred into corresponding analog bus signals.
Simultaneously the transceiver monitors the bus, converting the analog bus signals into the corresponding
digital bit stream, output at RXD.
5VCPFD[/QFG
Both the C250/251 and the TJA1040 offer a dedicated Standby Mode. In this mode the current
consumption is reduced to a minimum (e.g. <15µA max. for the TJA1040 and <170µA max. for the
C250). A dedicated low-power receiver ensures remote wake-up capability via the bus. The transmitter of
the TJA1040 and C250/251 is completely disabled in Standby Mode regardless of the signal on TXD.
This way the TJA1040 and C250/251 provides silent behaviour necessary to cope with "babbling idiot"
nodes. The main difference between the TJA1040 and the C250/251 in this mode concerns the bus bias.
While the C250/251 maintains a bus bias of Vcc/2, the TJA1040 pulls the bus weakly to GND. This
allows very low current consumption for the TJA1040 during low-power operation.
5NQRG%QPVTQN/QFG
The Slope Control Mode is provided by the C250/251 only. A resistor connected between the Rs pin and
GND level is used to adjust the slope. Due to the excellent symmetry performance, the TJA1050 and
TJA1040 do not need a slope control. They both feature a fixed slope, adjusted to optimize the EMC
performance and to minimize the loop delay. Even with the fixed slope EMC measurements revealed an
improvement of about 20dB in emission over the C250/251. Thus the TJA1040 and TJA1050 offer the
possibility to get rid of the common mode choke.
5KNGPV/QFG
The TJA1050 provides a dedicated Silent Mode, in which the transmitter is completely disabled, thus
making sure that no signal can be driven from TXD to the bus lines. As with the TJA1040 in its Standby
Mode this silent behaviour can be used to establish a "babbling idiot" protection. In Silent Mode the
receiver keeps active, thus implementing a "Receive-Only" behaviour.
6#4)'6#22.+%#6+105(146*'6,##0&6,#
Application of CAN High-Speed focuses on the powertrain bus. Here increasing power management
requirements established a kind of partial networking. During ignition-off (when the engine is off) one
part of the network is left un-powered by the "Clamp-15" supply line, while the other part keeps powered
all the time by the so-called "Clamp-30". Thus "Clamp-30" nodes need the possibility to minimize the
current consumption. Otherwise they would discharge the battery within a short time. Nodes switched off
completely during ignition-off must behave passive towards the remaining bus as far as possible.
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Nodes supplied permanently by the battery (Clamp-30)
use TJA1041
1041
1041
(Vcc on/off control)
1041
1040
1040
(ECU on/off)
1040
µC always active ?
use TJA1040
1050
(Vcc always on)
Nodes powered with ignition-on only (Clamp-15)
use TJA1050 (minimal bus loading)
or TJA1040 (no bus loading)
Figure 5.1: Target applications for the TJA1050 and TJA1040/1041
The TJA1041, capable of controlling the ECU voltage regulator(s) via the pin INH, focuses on
applications, which are supplied permanently by the battery. Its power management allows reducing the
current consumption of the whole ECU to max. 30µA, making use of an INH-controlled ECU voltage
regulator. For applications, which need the microcontroller and Vcc being always active, the TJA1040 is
preferred due to its very low-current Standby Mode (< 15µA). Both the TJA1040 and TJA1041 provide
remote wake-up capability via the bus.
For clamp-15 nodes, which are left un-powered during ignition-off, the TJA1050 or the TJA1040 are
preferred. Their passive behaviour in un-powered state ensures that the remaining bus will not be
degraded. With the TJA1040 there is even no bus loading.
+06'412'4#$+.+6;
Since the C250/251, TJA1050 and TJA1040, TJA1041 are compatible with the ISO11898 standard,
interoperability during normal operation is guaranteed. There is one issue related to the different bus
biasing behaviour during low-power operation, which shall be considered in more detail. Table 6.1 shows
the bus biasing in the different operation modes as well as in un-powered condition. Whenever there is a
difference in the bus biasing, a steady biasing compensation current will flow within the system. The
common mode input resistance mainly defines the amount of compensation current. This is shown in
Figure 6.1 for a bus in recessive state containing TJA1040 and C250 nodes. Due to the big common mode
input resistance CAN communication is not affected in case parts of the network are still within lowpower mode, while other nodes have already started communication. However, degradation of the
emission performance is expected.
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C250/251
Condition
TJA1050
TJA1040
Mode
Bus Bias
Mode
Bus Bias
Mode
Bus Bias
LOW (pin 8)
Normal
Vcc/2
Normal
Vcc/2
Normal
Vcc/2
HIGH (pin 8)
Standby
Vcc/2
Silent
Vcc/2
Standby
GND
Unconnected (pin 8)
Normal
Vcc/2
Normal
Vcc/2
Standby
GND
---
GND
---
GND
---
floating
Unpowered
Table 6.1: Bus biasing depending on operation mode
RCM,C250/nC250
RCM,1040/n1040
CANH
Icomp
Vcc/2
CANL
RCM,C250/nC250
RCM,1040/n1040
Powered
C250 nodes
TJA1040 nodes
in Standby
Figure 6.1: Equivalent bus circuit for a mixed system of TJA1040 nodes in Standby Mode and
powered C250 nodes (in Standby or Normal Mode)
The following formula allows calculation of the whole biasing compensation current in a mixed system of
TJA1040 and C250 nodes.
I comp ,max =
with
Vcc / 2
RCM (C 250) / 2nC 250 + RCM (TJA1040) / 2nTJA1040
nC 250 :
number of nodes of powered C250
nTJA1040 :
number of nodes of TJA1040 in Standby/Sleep Mode
RCM ,min (C 250) =5k:
min. common mode input resistance of C250 at pin CANH/L
RCM ,min (TJA1040) =15k:
min. common mode input resistance of TJA1040 at pin CANH/L
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Table 6.2 identifies the conditions leading to different bus biasing and thus compensation current. There
is some compensation current in case TJA1040 nodes are in Normal (Highspeed) Mode, while other
C250/C251/TJA1050 nodes are left un-powered. Moreover, compensation current occurs when TJA1040
nodes are in Standby Mode, while other C250/C251/TJA1050 nodes are kept powered in any operation
mode. Despite some compensation current flowing in this case the current saving effect using the
Standby Mode of the TJA1040 is higher than using the Standby Mode of the C250/251. The lowest
current consumption in such a mixed system will be achieved when the C250/C251/TJA1050 nodes are
left un-powered while the TJA1040 nodes are in Standby Mode.
C250/251
1050
All Modes
Unpowered
Normal/Highspeed
--
X
Standby
X
--
Unpowered
--
--
TJA1040
Table 6.2: Conditions leading to bus biasing compensation current
X
:
biasing compensation currents
-:
no biasing compensation currents
6,#OKZGFYKVJ6,#PQFGU
Table 6.3 reveals that in a mixed system of TJA1040 and TJA1041 nodes it is not expected to have
situations of different bus biasing. In the low-power modes both the TJA1040 and TJA1041 show a weak
termination to GND. Thus when the bus is in power-down with all nodes either in Standby or Sleep
Mode, there will be no biasing compensation currents. During normal CAN operation, when all nodes are
into Normal (Highspeed) or Pwon/Listen-Only mode for diagnosis features, the bus is collectively biased
to Vcc/2. There will be no biasing compensation current.
Normal/
Highspeed
Pwon/
Listen-Only
Standby
Sleep
Unpowered
Normal/Highspeed
--
--
X
X
X
Standby
X
X
--
--
--
Unpowered
--
--
--
--
--
TJA1041
TJA1040
Table 6.3: Combinations of operation modes of the TJA1040 and TJA1041
X
:
biasing compensation currents
-:
no biasing compensation currents
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Figure 7.1 and Figure 7.2 show a typical application circuit for the C250/251 and TJA1050, respectively.
Figure 7.3 shows the equivalent circuit for the TJA1040.
optional
TXD
TXD
Vref
RXD
RXD
CANH
CAN
bus
<100pF
uC
+
CAN
I/O
60 (1k3)*
Rs
C250/251
Rs
60 (1k3)*
4n7
VCC
Supply
CANL
CM Choke
VCC
100nF
GND
<100pF
GND
* For stub nodes a "weak" termination improves the EMC behaviour of the system in terms of emission.
Figure 7.1: Typical application circuit for the C250/251
optional
TXD
TXD
Vref
RXD
RXD
CANH
CAN
bus
<100pF
I/O
60 (1k3)*
S
uC
+
CAN
TJA1050
60 (1k3)*
4n7
VCC
Supply
CANL
<100pF
VCC
GND
100nF
GND
* For stub nodes a "weak" termination improves the EMC behaviour of the system in terms of emission.
Figure 7.2: Typical application circuit for the TJA1050
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optional
TXD
TXD
SPLIT
RXD
RXD
CANH
I/O
STB
CAN
bus
<100pF
uC
+
CAN
TJA1040
60 (1k3)*
60 (1k3)*
4n7
VCC
Supply
CANL
<100pF
VCC
GND
100nF
GND
* For stub nodes a "weak" termination improves the EMC behaviour of the system in terms of emission.
Figure 7.3: Typical application circuit for the TJA1040
*CTFYCTG%JGEM.KUV%→6,#
Comparing the application circuits in Figure 7.1 and Figure 7.2, the following things have to be checked
when replacing the C250/251 by the TJA1050:
-
If the mode control pin 8 of the C250 was applied with a slope control resistor Rs for slope control,
this resistor must be removed. The corresponding pin of the TJA1040 (pin "STB") should be directly
connected to an output port of the microcontroller.
-
Due to the excellent symmetry performance, the TJA1050 does not necessarily need a common mode
choke. However, the split termination is highly recommended as it ensures lowest emission, especially
in the AM-band.
*CTFYCTG%JGEM.KUV%→6,#
Comparing the application circuits in Figure 7.1 and Figure 7.3, the following things have to be checked
when replacing the C250/251 by the TJA1040:
-
If the pin "SPLIT" should be used for DC stabilization of the common mode voltage, the pin "SPLIT"
(corresponds to pin "Vref" of C250/251) is connected to the center tap of the split termination. The
pin "SPLIT" can simply be left open if not used.
-
If the mode control pin 8 of the C250 was applied with a slope control resistor Rs for slope control,
this resistor must be removed. The corresponding pin of the TJA1040 (pin "STB") should be directly
connected to an output port of the microcontroller.
-
The TJA1040 does not necessarily need a common mode choke. The split termination is highly
recommended as it ensures lowest emission, especially in the AM-band.
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4'('4'0%'5
[1]
Data Sheet PCA82C250, CAN controller interface, Philips Semiconductors, 2000 Jan 13
[2]
Data Sheet PCA82C251, CAN controller interface, Philips Semiconductors, 2000 Jan 13
[3]
Data Sheet TJA1050, High speed CAN transceiver, Philips Semiconductors, 2000 May 18
[4]
Preliminary Data Sheet TJA1040, High speed CAN transceiver, Philips Semiconductors, 2001
Nov 12
[5]
Preliminary Data Sheet TJA1041, High speed CAN transceiver, Philips Semiconductors, 2001
Nov 12
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