<p style=During the early stages of the project, a goal was set to maximize the value of the time and effort of design and verification. Several key decisions were made.

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These features ensure versatility of the 360-degree wraparound technology to meet the shortfalls of the conventional bird’s-eye methodology, and provide drivers with a complete, hemispheric look around their vehicles.

Figure 2: These waveforms show the behavior of the Figure 1 circuit when a DC supply is connected (a-upper) and disconnected (b-lower). Traces are: VSYS 5V/div, VDCIN 5V/div, IDCIN 1A/div, VPOK 5V/div, IBATT 1A/div, IMOSFET 1A/div.

RN65D2151FRE6_Vishay Dale_Through Hole Resistors

With the MOSFET, it drops to about 25mO (Figure 3 ):

RN65D2151FRE6_Vishay Dale_Through Hole Resistors

Figure 3: External MOSFET Q1 in Figure 1 lowers ON-resistance in the BAT-to-SYS switch from 60mO to 25mO.

To reduce the time delay between disconnecting the DC supply and turning on Q1, you can substitute smaller resistors for the 100kO values shown in Figure 1. With 10kO resistors, for example, Q1 picks up the load about 300µs sooner. Lower-value resistors have no effect on battery drain, because neither resistor passes current when SYS is using battery power (i.e., when active-low POK is high and Q1 is on). When DC power is applied, the circuit behavior with 10k? resistors is about the same as shown in Figure 2a.

RN65D2151FRE6_Vishay Dale_Through Hole Resistors

About the authorHubert Bugajski is an Applications Engineer (MTS) at Maxim Integrated Products (Sunnyvale, CA), where he has worked for over four years. He has an Electronics Engineering Technology diploma from Fanshawe College of Applied Arts and Technology (London Ontario, Canada), and a Bachelors of Electrical Engineering degree from Lakehead University (Thunder Bay, Ontario, Canada).

Together with the customer ASIC-relevant technical details are determined for the intended functions as well as the environmental influences on the functions, even when they are related to end customer usage; additionally, this phase can uncover something that will be reported as necessary diagnosis functions of the ASIC.

Usually it is very easy to find the things needed for proper functioning. More effort will go into determining how to cover all the possible influences which might prevent the ASIC from doing its job properly, especially when the ASIC is expected to determine if its data are valid or corrupt (detection action), because this is one of the most important tasks for automotive electronics. Also designers can sort out what the ASIC cannot fix or detect without cost-intensive extensions to the first draft of the ASIC requirement specification.

What is the difference between using an FMEA tool or the FMEA methodology idea in comparison to the classical check list approach? It’s simple: Designers can be more complete when translating customer requirements into parameter specifications for the ASIC because the detailed discussion of functions, diagnostics, and possible malfunctions at top level were already completed. The FMEA tool makes them visible regarding functional trees or failure trees, and designers can automatically give them an ID. When a characteristic has an ID it is identified and therefore visible,” and designers can check only visible items for completeness.

Once this is done, the designer can translate the system FMEA outcome to an ASIC parameter specification. This way the ASIC functions and their electrical parameters are captured, along with the unique ID of every specified parameter. The ID is necessary for tracking and also for change management when the requirement specifications are changed.

Breakdown to buildup From the ASIC functions it is possible to derive the needed building blocks using the work-breakdown structure (WBS) approach. This method can be used to identify the blocks for the design FMEA. In the best case, they correspond closely, or 1:1, to your WBS. Perhaps, however, the specifying individual responsible will define the right WBS level to be used. If well defined, the same blocks will occur in the project plan which gives a very consistent picture of the project without any additional cost. Also this approach covers the automotive SPICE requirement of traceability of parameters and their changes thoughout the project.

A boost LED driver can power multiple LEDs simultaneously by boosting a lower input voltage (from the lithium ion battery) to a higher output voltage (across the LEDs). The higher output voltage is used to forward bias a string of LEDs in series. Depending upon how much voltage the boost can handle, it can drive multiple LEDs at the same.

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