Design Article
Intelligent multiplexer upgrades automotive lighting high side drivers
Luc Dang, STMicroelectronics
12/9/2010 8:18 PM EST
Intelligent multiplexer lowers MCU workload and increases system robustness
The L99PD08, also called AMICO (Advanced Multiplexed and Integrated Co-processor), is an intelligent multiplexer, which controls and performs the diagnostic of 8 HSD channels.
The HSDs can be selected within the STMicroelectronics VIPOWER M0-5, M0-5E, and M0-5T families, regardless of the Rdson, the type of diagnostic, or the number of channels per device. The L99PD08 interfaces between the microntroller and the high side drivers. The device communicates with the microcontroller through an SPI interface, which reduces the required MCU pin count from 32 down to 11 for 16 HSD channels (see below).
The 8-bit resolution PWM is derived from two external clocks. In order to prevent a high voltage drop caused by simultaneous inrush current to multiple bulbs, and to improve the electromagnetic compatibility of the system, the L99PD08 can introduce a phase shift to any output channel. The device simultaneously monitors 8 HSD channels, by sampling each diagnostic signal every 32 µs. This real time diagnostic always takes into account whether the sampling is done while the HSD is in on-state or off-state. The resulting synchronous process avoids wrong diagnostics when PWM is applied.
The reaction time of the L99PD08 in case of a shorted HSDs stretches from 64 to 100 µs, in order to filter potential effects caused by fast ISO-type transients. The optional latch-off done by the L99PD08 improves the short circuit robustness of the HSDs, without any intervention of the microcontroller. Evaluations under conditions specified by AECQ100-012 show an improvement factor of more than 300 at -40C during the long pulse test (300 ms reaction time before turn off, see below), compared to a direct diagnostic of the HSD by the MCU.
Conclusion
The L99PD08 makes the challenging requirements of modern body controller modules easier to fulfill. The on-board PWM generation with phase shift, synchronous diagnostics, and fast reaction time in short circuit conditions lower microcontroller workload and increase the robustness of the HSDs. The AMICO also virtually upgrades the HSDs of the M0-5, M0-5E, and M0-5T families with a SPI interface—which decreases the microcontroller required pin count, for both 12 and 24V applications. There is also a reduction in software complexity, which is becoming more of a challenge—specifically with the introduction of AUTOSAR.
Luc Dang is technical marketing engineer, Automotive Applications, at STMicroelectronics.
The L99PD08, also called AMICO (Advanced Multiplexed and Integrated Co-processor), is an intelligent multiplexer, which controls and performs the diagnostic of 8 HSD channels.
The HSDs can be selected within the STMicroelectronics VIPOWER M0-5, M0-5E, and M0-5T families, regardless of the Rdson, the type of diagnostic, or the number of channels per device. The L99PD08 interfaces between the microntroller and the high side drivers. The device communicates with the microcontroller through an SPI interface, which reduces the required MCU pin count from 32 down to 11 for 16 HSD channels (see below).
The 8-bit resolution PWM is derived from two external clocks. In order to prevent a high voltage drop caused by simultaneous inrush current to multiple bulbs, and to improve the electromagnetic compatibility of the system, the L99PD08 can introduce a phase shift to any output channel. The device simultaneously monitors 8 HSD channels, by sampling each diagnostic signal every 32 µs. This real time diagnostic always takes into account whether the sampling is done while the HSD is in on-state or off-state. The resulting synchronous process avoids wrong diagnostics when PWM is applied.
The reaction time of the L99PD08 in case of a shorted HSDs stretches from 64 to 100 µs, in order to filter potential effects caused by fast ISO-type transients. The optional latch-off done by the L99PD08 improves the short circuit robustness of the HSDs, without any intervention of the microcontroller. Evaluations under conditions specified by AECQ100-012 show an improvement factor of more than 300 at -40C during the long pulse test (300 ms reaction time before turn off, see below), compared to a direct diagnostic of the HSD by the MCU.
Automatic latch off provides robustness under short circuit conditions.
Conclusion
The L99PD08 makes the challenging requirements of modern body controller modules easier to fulfill. The on-board PWM generation with phase shift, synchronous diagnostics, and fast reaction time in short circuit conditions lower microcontroller workload and increase the robustness of the HSDs. The AMICO also virtually upgrades the HSDs of the M0-5, M0-5E, and M0-5T families with a SPI interface—which decreases the microcontroller required pin count, for both 12 and 24V applications. There is also a reduction in software complexity, which is becoming more of a challenge—specifically with the introduction of AUTOSAR.
Luc Dang is technical marketing engineer, Automotive Applications, at STMicroelectronics.
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Dr DSP
12/15/2010 1:20 PM EST
Are there specific parts of AUTOSAR that the L99PD08 helps with? It would be nice to include them in this article.
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