AMIS-42770 Dual High-Speed CAN Transceiver
For Long Networks
Data Sheet
7.7 Power-on-Reset (POR)
While Vcc voltage is below the POR level, the POR circuit makes sure that:
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The counters are kept in the reset mode and stable state without current consumption
Inputs are disabled (don't care)
Outputs are high impedant; only Rx0 = high-level
Analog blocks are in power down
Oscillator not running and in power down
CANHx and CANLx are recessive
VREF output high impedant for POR not released
7.8 Over Temperature Detection
A thermal protection circuit is integrated to prevent the transceiver from damage if the junction temperature exceeds thermal
shutdown level. Because the transmitters dissipate most of the total power, the transmitters will be switched off only to reduce
power dissipation and IC temperature. All other IC functions continue to operate.
7.9 Fault Behavior
A fault like a short circuit is limited to that bus line where it occurs; hence data interchange from the protocol IC to the other bus
system is not affected.
When the voltage at the bus lines is going out of the normal operating range (-12V to +12V), the receiver is not allowed to
erroneously detect a dominant state.
7.10 Short Circuits
As specified in the maximum ratings, short circuits of the bus wires CANHx and CANLx to the positive supply voltage Vbat or to
ground must not destroy the transceiver. A short circuit between CANHx and CANLx must not destroy the IC as well.
7.11 Faulty Supply
In case of a faulty supply (missing connection of the electronic unit or the transceiver to ground, missing connection of the
electronic unit to Vbat or missing connection of the transceiver to Vcc), the power supply module of the electronic unit will operate
such that the transceiver is not supplied, i.e. the voltage Vcc is below the POR level. In this condition the bus connections of the
transceiver must be in the POR state.
If the ground line of the electronic unit is interrupted, Vbat may be applied to the Vcc pin (measured relative to the original ground
potential, to which the other units on the bus are connected).
7.12 Reverse Electronic Unit (ECU) Supply
If the connections for ground and supply voltage of an electronic unit (ECU) (max. 50V) which provides Vcc for the transceiver are
exchanged, this transceiver has a ground potential which may be up to 50V higher than that of the other transceivers. In this case
no transceiver must be destroyed even if several of them are connected via the bus system.
Any exchange among the six connections CANH1, CANH2, CANL1, CANL2, ground, and supply voltage of the electronic unit at
the connector of the unit must never lead to the destruction of any transceiver of the bus system.
AMI Semiconductor
– October 2007, Rev. 1.0
www.amis.com
Specifications subject to change without notice
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AMI [ AMI SEMICONDUCTOR ]
