Open-load conditions and a design example
In the case of an open-load condition, the according status register is latched. The status can be read and optionally cleared by the SPI. The high-side driver is not switched off. In the case of a fail-safe condition, the high-side drivers are switched off. The control bits are set to default values (except OUT1/FSO if it is used as a high-side output).
The outputs, REL1, REL2 (RDSon = 2Ω typical at 25C), are especially designed to drive relay loads. Typical relays used have the following characteristics:
Relay type 1: ON-state: R = 160Ω typical +10%, L = 300 mH: Off-state: 240 mH
Relay type 2: ON-state: R = 220Ω typical +10 %, L = 420 mH: Off-state: 330 mH
The outputs provide an active output Zener clamping (44V typical) feature for the demagnetization of the relay coil, even though a load dump condition exists.
The low-side drivers switch off in case of:
● VS over-voltage and under-voltage (can be masked by SPI)
Low-side protection works in the same way as high-side outputs.
Digital diagnosis features are provided by the SPI and include:
● V1 reset threshold programmable
● Over-temperature including pre-warning
● Open-load separately for each OUT1,2
● Overload status separately for each output stage
● VS-supply over-voltage/under-voltage
● V1-fail bit
● V1 under-voltage
● Chip reset bit (start from power-on reset)
● Number of unsuccessful V1 restarts after thermal shutdown
● Number of sequential watchdog failures
● LIN diagnosis (permanent recessive/dominant, dominant TxD)
● Device state (wake-up from V1stby or Vbatstby)
● Forced Vbatstby after WD-fail, forced Vbatstby after over-temperature
● Watchdog timer state (diagnosis of watchdog)
● Fail safe status
● SPI communication error
An application diagram for a mechatronic window lift, based on L99PM60J adoption, is shown below.
It is useful to highlight that there is no microprocessor core within the device. Thus the L99PM60J is particularly useful for those applications where the use of a particular microcontroller is dictated by its presence on the approved BoM list of the car manufacturer–and a new microprocessor, for timing constraints or any other reason, is not allowed.
Packaging technology has evolved toward a surface mount approach even for low- to medium-power applications. System miniaturization requires thinner packages with an improved ratio between silicon die area and package footprint. The reduction of interconnections among chips, while simplifying the design, also decreases the assembly cost, increases system density, and improves reliability of the system. The device comes with a compact power package, the PowerSSO-16, with exposed pad technology. Such a package offers very good thermal performance that is useful if the adopted PCB is, for example, a simple FR4, double layer instead of a more powerful four layer PCB plus vias.
Thus, such a mechatronic control architecture can simplify the electrical distribution system, improve quality and reliability—and lead to reduced power consumption and emissions.
About the author
Giovanni Luca Torrisi
in 1995. As an IC designer, he worked in the field of power electronics (designing electronic ignitions and AC/AC converters for Halogen Lamps); in these areas, he holds several patents. In 2002 he joined the technical marketing team and now leads a group, covering USA and Japan areas, responsible for automotive body products for ST.
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