TLE6254-2G Datasheet, PDF (7/24 Pages) Infineon Technologies AG – Fault Tolerant Differential CAN-Transceiver

Final Data TLE 6254-2G
Circuit Description
5.1
Operation Modes, Wake-Up
In addition to the normal operation mode, the TLE 6254-2G offers a receive-only mode
as well as two low power operation modes to save power during periods that do not
require communication on the CAN bus: sleep mode, V_Bat stand-by mode (see Table 2
and Figure 4). Via the control input pins NSTB and ENT the operation modes are
selected by the microcontroller. In the low power modes neither receiving nor
transmitting of messages is possible.
In sleep operation mode the lowest power consumption is achieved. In order to minimize
the overall current consumption of the ECU (electronic control unit) the external voltage
regulator (5 V supply) is deactivated by the INH output in this mode, when connected.
For that purpose the INH output is switched to high impedance. In parallel the CANL line
is pulled-up to the battery supply voltage via the RTL output and the pull-up paths at the
input pins TxD and RxD are disabled from the internal supply.
To enter the sleep operation mode the transition mode “Go-to-Sleep” has to be selected
(Figure 4) for a minimum time t_h(min). After the minimum hold time t_h(min) the sleep mode
can be actively selected. Otherwise the TLE 6254-2G will automatically fall in sleep
mode because of the not powered microcontroller.
On a wake-up request either by bus line activities or via the WAKE input, the transceiver
is automatically set in V_Bat-stand-by mode. Now the voltage regulator (5 V supply) is
enabled by the INH output. The WAKE input reacts to both, transition from high to low
voltage level as well as the other way round. To avoid faulty wake-ups due to transients
on the bus lines or the WAKE input circuitry respectively, a certain filter time is
implemented. As soon as V_CC is provided, the wake-up request is monitored on both, the
NERR and RxD outputs, by setting them low. Upon this the microcontroller can activate
the normal operation mode by setting the control inputs NSTB and ENT high.
The V_Bat stand-by mode corresponds to the sleep mode, but a voltage regulator
connected to the INH output will remain active. Wake-up requests via the WAKE pin or
the bus lines are immediately reported to the microcontroller by setting RxD and NERR
low. A power-on condition (V_BAT pin is supplied) automatically switches the TLE 6254-2G
to V_Bat stand-by mode.
In the receive-only mode data on the CAN-bus are transvered to the RxD output, but both
output stages, CANH as well as CANL are disabled. This means that data at the TxD
input are not transmitted to the CAN bus. This mode is useful in combination to a
dedicated network-management software that allows separate diagnosis for all nodes.
A wake-up request in the receive-only mode is only reported at the RxD-output. The
NERR output in this mode is used to indicate a battery fail condition. When entering the
normal mode the V_bat-flag is reset and the NERR output becomes high again. This
feature is useful e.g. when changing the ECU and therefore a presetting routine of the
microcontroller has to be started.
Data Sheet Version 1.4
7
2003-07-22