TLE8263-2E Datasheet, PDF (66/94 Pages) Infineon Technologies AG – Universal System Basis Chip

TLE8263-2E
Confidential
Limp Home
13
Limp Home
13.1
Description
The Limp Home outputs are a very useful way to control safety critical functions independent of the microcontroller,
such as turning on or off critical load during a microcontroller failure.
13.2
Limp Home output
The Limp Home output is an active LOW open drain transistor, please refer to Figure 31; therefore, it is necessary
to connect at least an external pull-up resistor at.
The Limp Home output is activated due to a failure condition or via SPI, see Chapter 13.3. If V_s is below V_LHUV,
the Limp Home cannot be activated and remains as a high impedance.
Limp home logic
Limp home
LIMP HOME.VSD
Figure 31 Limp Home block diagram
13.2.1 Limp Home side indicators output
The LH_SI output is similar to the Limp Home output. The output is pulsed to f_LHSI frequency with d_SI and designed
to provide the side indicators frequency. The LH_SI function is active when the Limp Home is active.
Limp home logic
Limp home
LH_SI
Figure 32 Limp Home LH_SI block diagram
LIMP HOME_LHSI.VSD
13.2.2 LH_PL (Pulsed Light) output
The LH_PL/Test pin is an output pin shared with the Test pin function. During SBC Init Mode, the pin is used as
an input, in all other modes, the pin is an output.
The output is pulsed to f_LHPL frequency with a duty cycle of d_PL (20% LOW, 80% high impedance), designed to dim
the 27W stop lights into an 5W rear light. Refer to Figure 33. The LH_PL function is activated when the Limp Home
is active. In SBC Init Mode, the LH_PL is inhibited, to avoid a wrong set of the SBC into SBC Software development
Mode.
Data Sheet
66
Rev. 1.0, 2009-03-31