One major trend that we’ve all noticed in automobiles over the past few years is the use of cameras-- for assistance when backing up. Just 10 or 20 years ago, such technology was unheard of in the United States. By 2018, it will become mandatory in all new vehicles. Some automobile manufacturers are even looking to install more than one camera per vehicle to provide more driver assistance and safety. Clearly, this market is becoming essential which demands an optimized yet flexible design, allowing for design compatibility across a number of different models.
Almost all of these cameras receive their power from a protected and semi-regulated form of the battery’s voltage. The individual camera does not need to incorporate all of the expensive and bulky circuitry necessary to operate directly from the battery and to support the voltage transients that come with cold crank and other harsh operations. This configuration reduces the cost and size of each camera.
On the other hand, the power supplied to the camera is not from a perfectly regulated source. To reduce weight, the power wires are typically very thin. In other cases, the power is delivered over a coaxial-type cable (“power over coax”) and not dedicated power cables. This method reduces the extra weight of all cables.
In either case, such thin cables necessarily have significant voltage drop across them. This causes the voltage at the camera end of the cable to vary dramatically based on the length of each cable to each camera. Different vehicle types have different lengths of cable, creating the need for a flexible solution for common power architecture, which can be used for all vehicle cameras. Such a solution needs to be small and cost-effective.
This TI Design shows a flexible, small, and cost-effective solution for a camera module. The solution shown above next to a USA quarter-dollar coin uses the automotive-qualified TPS62170-Q1 to operate directly from power sources such as coaxial cables. The wide 3-V to 17-V operating input voltage range makes this device well-suited for a variety of semi-regulated input power sources. The 2-mm x 2-mm IC package enables a total solution size of under 50 mm2. A second voltage rail on this camera module reference design is created from the smaller TPS62231-Q1, which comes in a 1-mm x 1.5-mm IC package., supporting a 12-mm2 total solution size.
In addition to the small IC size and high integration enabling a very small total solution size, the DCS-Control topology of these two devices gives excellent noise performance and eliminates the need for post-switching converter linear regulators (LDOs). The noise performance of these two switching converters is sufficient for the application with simple and low cost resistor-capacitor (RC) filters installed where needed. A higher efficiency solution with lower self-heating and less Bill of Materials (BOM) cost results.
What trends do you see in automotive camera modules?