INTEGRATED CIRCUITS
AU5790
Single wire CAN transceiver
Preliminary specification |
1999 Oct 28 |
Supersedes data of 1998 Mar 10
IC18 Data Handbook
P s
on o s
Philips Semiconductors |
Preliminary specification |
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Single wire CAN transceiver |
AU5790 |
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FEATURES
•Supports in-vehicle class B multiplexing via a single bus line with ground return
•33 kbps CAN bus speed with loading as per J2411, up to 41.6 kbps with modified loading
•83 or 100 kbps high-speed transmission mode
•Low RFI due to output waveshaping
•Direct battery operation with protection against load dump, jump start and transients
•Bus terminal protected against short-circuits and transients in the automotive environment
•Built-in loss of ground protection
•Thermal overload protection
•Supports communication between control units even when network in low-power state
•70 μA typical power consumption in sleep mode
•8-pin SOIC
•Fully integrated receiver filter
•±8kV ESD protection on bus and battery pins
DESCRIPTION
The AU5790 is a line transceiver, primarily intended for in-vehicle multiplex applications. The device provides interfacing between a
CAN data link controller and a single wire physical bus line. The achievable bus speed is primarily a function of the network time constant and bit timing, e.g., up to 41.6 kbps with a network including 32 bus nodes. The AU5790 provides advanced sleep-/wake-up functions to minimize power consumption when a vehicle is parked, while offering the desired control functions of the network at the same time. Fast transfer of larger blocks of data is supported using the high-speed data transmission mode.
PIN CONFIGURATION
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TxD |
1 |
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8 |
GND |
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NSTB (Mode 0) |
2 |
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7 |
CANH (BUS) |
EN (Mode 1) |
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AU5790 |
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RTH (Load) |
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3 |
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6 |
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RxD |
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4 |
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5 |
BAT |
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SO8 |
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SL01198 |
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QUICK REFERENCE DATA
SYMBOL |
PARAMETER |
CONDITIONS |
MIN. |
TYP. |
MAX. |
UNIT |
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VBAT |
Operating supply voltage |
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5.5 |
12 |
27 |
V |
Tamb |
Operating ambient temperature |
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±40 |
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+125 |
°C |
VBATD |
Battery voltage |
load dump; 1s |
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+45 |
V |
VCAN_N |
Bus output voltage |
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3.6 |
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4.55 |
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VT |
Bus input threshold |
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1.8 |
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2.2 |
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tBO |
Bus output delay |
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7.2 |
μs |
tBI |
Bus input delay |
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1 |
μs |
IBATS |
Sleep mode supply current |
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70 |
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μA |
ORDERING INFORMATION
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DESCRIPTION |
TEMPERATURE RANGE |
ORDER CODE |
DWG # |
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SO8: |
8-pin plastic small outline package; packed in tubes |
±40_ to +125_C |
AU5790D |
SOT96±1 |
SO8: |
8-pin plastic small outline package; packed on tape and reel |
±40_ to +125_C |
AU5790D±T |
SOT96±1 |
1999 Oct 28 |
2 |
Philips Semiconductors |
Preliminary specification |
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Single wire CAN transceiver |
AU5790 |
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BLOCK DIAGRAM
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BATTERY (+12V) |
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BAT |
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1 |
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VOLTAGE |
TEMP. |
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REFERENCE |
PROTECTION |
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TxD |
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OUTPUT |
7 |
CANH |
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BUFFER |
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NSTB |
3 |
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(Mode 0) |
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MODE |
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CONTROL |
BUS |
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EN |
6 |
RECEIVER |
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(Mode 1) |
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RT |
RxD |
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4 |
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5 |
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LOSS OF |
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GROUND |
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PROTECTION |
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RTH |
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(LOAD) |
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AU5790 |
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8 |
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GND |
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SL01199
Figure 1. Block Diagram
1999 Oct 28 |
3 |
Philips Semiconductors |
Preliminary specification |
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Single wire CAN transceiver |
AU5790 |
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PIN DESCRIPTION
SYMBOL |
PIN |
DESCRIPTION |
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TxD |
1 |
Transmit data input; high: transmitter passive; low: transmitter active |
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NSTB (Mode 0) |
2 |
Stand-by control; high: normal and high-speed mode; low: sleep and wake-up mode |
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EN (Mode 1) |
3 |
Enable control; high: normal and wake-up mode; low: sleep and high-speed mode |
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RxD |
4 |
Receive data output; low: active bus condition detected; float/high: passive bus condition detected |
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BAT |
5 |
Battery supply input (12V nom.) |
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RTH |
6 |
Switched ground pin, pulls the load to ground, except in case the module ground is disconnected |
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CANH |
7 |
Bus line transmit input/output |
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GND |
8 |
Ground |
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FUNCTIONAL DESCRIPTION
The AU5790 is an integrated line transceiver IC that interfaces a CAN protocol controller to the vehicle's multiplexed bus line. It is primarily intended for automotive ªClass Bº multiplexing applications in passenger cars using a single wire bus line with ground return. The achievable bit rate is primarily a function of the network time constant and the bit timing parameters. For example, the maximum bus speed is 33 kbps with bus loading as specified in J2411 for a full
32 node bus, while 41.6 kbps is possible with modified bus loading. The AU5790 also supports a low-power sleep mode to help meet ignition-off current draw requirements.
The protocol controller feeds the transmit data stream to the transceiver's TxD input. The AU5790 transceiver converts the TxD data input to a bus signal with controlled slew rate and waveshaping to minimize emissions. The bus output signal is transmitted via the
CANH in/output, connected to the physical bus line. If TxD is low, then a typical voltage of 4V is output at the CANH pin. If TxD is high, then the CANH output is pulled passive low via the local bus load resistance RT. To provide protection against disconnection of the module ground, the resistor RT is connected to the RTH pin of the
AU5790. By providing this switched ground pin, no current can flow from the floating module ground to the bus. The bus receiver detects the data stream on the bus line. The data signal is output at the RxD pin being connected to a CAN controller. The AU5790 provides appropriate filtering to ensure low susceptibility against electromagnetic interference. Further enhancement is possible by applying an external capacitor between CANH and ground potential. The device features low bus output leakage current at power supply failure situations.
If the NSTB and EN control inputs are pulled low or floating, the
AU5790 enters a low-power or ªsleepº mode. This mode is dedicated to minimizing ignition-off current drain, to enhance system efficiency. In sleep mode, the bus transmit function is disabled,
e.g., the CANH output is inactive even when TxD is pulled low. An internal network active detector monitors the bus for any occurrence of signal edges on the bus line. If such edges are detected, this will be signalled to the CAN controller via the RxD output. Normal transmission mode will be entered again upon a high level being applied to the NSTB and EN control inputs. These signals are typically being provided by a controller device.
Sleeping bus nodes will generally ignore normal communication on the bus. They should be activated using the dedicated wake-up mode. When NSTB is low and EN is high the AU5790 enters wake-up mode, i.e., it sends data with an increased signal level.
This will result in an activation of other bus nodes being attached to the network.
The AU5790 also provides a high-speed transmission mode, supporting bit rates up to 100 kbps. If the NSTB input is pulled high and the EN input is low, then the internal waveshaping function is disabled, i.e., the bus driver is turned on and off as fast as possible to support high-speed transmission of data. Consequently, the EMC performance is degraded in this mode compared to the normal transmission mode. In high-speed transmission mode the AU5790 supports the bus signal levels as specified for the CANH output of the fault-tolerant CAN transceiver TJA1054.
The AU5790 features special robustness at its BAT and CANH pins. Hence the device is well suited for applications in the automotive environment. The BAT input is protected against 45V load dump and jump start conditions. The CANH output is protected against wiring fault conditions, e.g., short circuit to ground or battery voltage as well as typical automotive transients. In addition, an over-temperature shutdown function with hysteresis is incorporated protecting the device under system fault conditions. In case of the chip temperature reaching the trip point, the AU5790 will latch-off the transmit function. The transmit function is available again after a small decrease of the chip temperature.
Table 1. Control Input Summary
NSTB |
EN |
TxD |
Description |
CANH |
RxD |
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0 |
0 |
don't care |
Sleep mode |
0V |
float (high) |
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0 |
1 |
Tx-data |
Wake-up transmission mode |
0V, 12V |
bus state1 |
1 |
0 |
Tx-data |
High-speed transmission mode |
0V, 4V |
bus state1 |
1 |
1 |
Tx-data |
Normal transmission mode |
0V, 4V |
bus state1 |
NOTE:
1.RxD outputs the bus state. If the bus level is below the receiver threshold (i.e., all transmitters passive), then RxD will be floating (i.e., high, considering external pull-up resistance). Otherwise, if the bus level is above the receiver threshold (i.e., at least one transmitter is active), then RxD will be low.
1999 Oct 28 |
4 |
Philips Semiconductors |
Preliminary specification |
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Single wire CAN transceiver |
AU5790 |
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TEST CIRCUITS
TxD |
NSTB |
EN |
RxD |
2.4 kΩ |
5.1V |
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GND |
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CANH |
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AU5790 |
RTH |
2.4 kΩ |
1 μF |
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BAT |
9.1 kΩ |
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S3 |
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I_CAN_LG |
VBAT |
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SL01234 |
Figure 2. Loss of ground test circuit
NOTES:
Opening S3 simulates loss of module ground.
Check I_CAN_LG with the following switch positions:
1.S1 = open = S2
2.S1 = open, S2 = closed
3.S1 = closed, S2 = open
4.S1 = closed = S2
1999 Oct 28 |
5 |
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