TLE6263 datasheet(15/40 Pages) INFINEON

15 / 40 page

Final Datasheet TLE 6263

Version 2.08

2004-06-07

6.8

Fail Safe feature

The output FSO becomes HIGH when the watchdog is correctly serviced by the

microcontroller for the fourth time. As soon as either an under-voltage reset or watchdog

reset occurs, it is set LOW again. This feature is very useful to control critical applications

independent of the due function of the microcontroller e.g. to disable the power supply

in case of a microcontroller failure.

6.9

Sense Comparator (pin SI) and VINT-fail

The sense comparator (early warning function) compares a voltage defined by the user

to an internal reference voltage. Therefore the voltage to be supervised has to be scaled

down by an external voltage divider in order to compare it to the internal sense threshold

VSIth. This feature can be used e.g. to supervise the battery voltage in front of the reverse

protection diode. The microcontroller is given a pre-warning before an under-voltage

reset due to low input voltage occurs. The pre-warning is flagged by setting the interrupt

output INT low in normal mode, receive only mode and Vbat-stand-by mode. In sleep

operation mode the sense function is inactive. Calculation of the voltage divider can be

easily done since the sense input current can be neglected. An internal blanking time

prevents from false triggering due to line transients. Further improvement is possible by

the use of an external ceramic capacitor switched between SI and GND (see Application

Diagram Figure 15).

6.10

VINT- and VCC-fail flag

To activate the VINT supervisor feature the SPI IBIT 6 has to be set HIGH to set an

internal flip-flop. This automatically sets the Vbat-stand-by OBIT 6 HIGH, too. Should the

internal supply voltage become lower than the internal threshold VVINT,th (typ. 2.5V) the

NOT VINT-Fail bit becomes LOW to indicate the low voltage condition. All SPI input

registers are set LOW due to a low voltage condition of the internal supply voltage.

Like the wake-up diagnosis the VINT-Fail diagnosis can only be monitored in the Vbat-

stand-by mode. The VINT-Fail feature can also be used to give an indication when the

ECU has been changed and therefore a pre-setting routine of the microcontroller has to

be started.

Further to the reset threshold there is another supervisor threshold implemented, to

monitor the output voltage VCC. This threshold is called VVCC,th (typ. 2.5V). The NOT

VCC-Fail feature is monitored via OBIT 7 in the Vbat-stand-by mode and set, like the NOT

VINT-Fail flag, via IBIT 6 (so both fail features are activated with the IBIT 6 but monitored

via OBIT 6 and OBIT 7 during Vbat-stand-by).

In the receive-only mode both fail bits cause the interrupt output INT to go low.

TLE6263 Datasheet(PDF) 15 Page - Infineon Technologies AG