Infineon TLE8457

TLE8457

LIN Transceiver with integrated Voltage Regulator

Functional Description

4.4

Initialization Watchdog

The TLE8457 features an enhanced Initialization Watchdog timer for detection of local failures and error handling for minimizing system current consumption. The benefit of this safety function is to prevent a malfunctioning ECU being stuck in Init Mode with high current consumption and draining the car battery. The

Initialization Watchdog is only active in Init Mode, with the two use cases: V

Operation Mode activation.

CC

supply initialization and Normal

V

S

1

V

S,PON

2

V

CC,UV

V

CC

NRST

Watchdog

V

CC

Supply Initialization

Timeout

1

t

RST

3

Normal Operation mode Activation

Timeout

2

5

t

to,rec

EN

Un-powered Init mode

4

Normal Operation mode

If Timeout → forced transition to Sleep mode If Timeout → forced transition to Sleep mode

4

5

1

2

3

V

S

exceeds the Power-on reset threshold →

V

CC

Supply Initialization Watchdog is started

V

CC

exceeds the

V

CC

-Undervoltage threshold → Reset timer is started

Reset timer elapses → Normal Operation mode Activation Watchdog is started

Mode change with the EN input → Mode transition to normal mode

TxD must be „high“ for at least

t

to,rec

after entering Normal mode for releasing the transmitter

TLE8457_WATCHDOG

Figure 12 Initialization Watchdog

VCC Supply Initialization

The V

CC

supply Initialization watchdog is detecting if local errors on the ECU is preventing the V

CC

supply to power up correctly because of short circuits to ground or if components on the board are drawing too high currents. The timer is started when the linear regulator is switched on after power-up events or after mode transitions to Init mode triggered by either bus wake-up or the EN input being set “high” in Sleep Mode.

Additionally, the timer will start when detecting V event.

CC

undervoltage and after recovery from an overtemperature

Data Sheet 15 Rev. 1.0

2016-08-05

TLE8457

LIN Transceiver with integrated Voltage Regulator

Functional Description

In case the V

CC

voltage rise above the V

CC,UV

undervoltage threshold before the timer elapses, V

CC successfully initialized and the timer is disabled. If the timer elapses before V

CC

TLE8457 will autonomously transition to Sleep Mode.

is considered

powers up correctly, the

Normal Operation Mode Activation

After the TLE8457 has generated a reset pulse the Initialization Watchdog is started for monitoring the activation of Normal Operation Mode. The microcontroller must set the EN input “high” before the timer elapses after t

Init_WD

, else the TLE8457 will autonomously transition to Sleep Mode.

t

Init_WD

EN tt

t

RST

NRST

Standby mode / Sleep mode / unpowered

Figure 13 Enable activation time-out

Init mode t

Sleep mode

TLE8457_INITIALIZATION_TIMEOUT

Data Sheet 16 Rev. 1.0

2016-08-05