![]() Strictly Necessary Cookies: (Always Active) These cookies are necessary for the website to function and cannot be switched off in our systems. After we finish updating our website, you will be able to set your cookie preferences. ![]() At light load, this circuit maintains regulations with input down to 2 V.Īnalog Devices is in the process of updating our website. Figure 2 shows an easy way to generate four accurately regulated outputs. By running the bucks at optimal efficiency, the temperature rise is well controlled. In Figure 2, the fourth channel is set up as a SEPIC to power the high voltage bucks, with its output regulated at 12 V, which is optimal for the buck regulator efficiency. The temperature rise can be controlled by either reducing the switching frequency or reducing the operating voltage of the buck regulators. This has no effect on the boost regulator in Figure 1-V BAT passes through when V BAT is higher than 8 V-but the current output capacities of the two high voltage buck regulators are typically thermally limited at higher V BAT due to increased switching losses, especially at 2 MHz switching frequency that is often used in automotive applications. V BAT can remain high for an extended period of time, such as during a double battery jump-start or in a 24 V system. Four Regulated Outputs with the Fourth Rail as SEPIC Three bucks are powered with a boost preregulator (V OUT4), yielding precise regulation for all three outputs through a V BAT cold crank event (also shown). Cold crank tolerant automotive supply with three regulated outputs. In Figure 1, the low voltage buck is powered from OUT2, providing 1.2 V through the cold crank event.įigure 1. The high voltage bucks can handle V BAT up to 42 V. Once V BAT recovers to above 8 V from the cold crank, the boost controller simply works as diode through. The two high voltage bucks can ride through the cold crank condition while providing constant 5 V and 3.3 V outputs, as shown in Figure 1. When V BAT drops below 8.5 V, the boost controller output (OUT4) is regulated to 8 V. The LT8603 boost controller operates down to 2 V, making it ideal as a preregulator to power the buck regulators. High efficiency step-down buck regulators cover most situations, but V BAT can drop to 2 V for 10s of ms during a cold crank situation, where pure buck regulators would lose regulation if powered directly from V BAT. These rails are generated from the nominal 12 V automotive battery voltage V BAT, which typically ranges from 8 V to 16 V. ![]() In automobile applications, regulated 5 V, 3.3 V, and sub-2 V rails are required to power various analog and digital ICs that may require different rails for content, the processor I/O, and the core. Four regulated outputs with a fourth rail as SEPICĬold Crank Tolerant Automotive Supply with Three Regulated Outputs. ![]()
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