Today infotainment systems are the personal electronics inside automobiles. Like personal electronics, automotive infotainment systems integrate many electronics in space constrained head units and instrument clusters to process various kinds of signals. One critical challenge for infotainment OEMs and suppliers designing these compact and feature-rich infotainment systems is delivering clean power rails to noise-sensitive applications such as audio codecs, gesture sensors, microprocessor digital radios, GPS, and Wi-Fi.
One highly efficient way to provide cleaner power is using a linear regulator and switching regulator solution to transfer power from the automotive battery. Switching regulators are the most efficient method to convert DC power, but they are notorious for their ripples and EMI--especially in noise-sensitive infotainment applications. By adding a low-noise and high-PSRR LDO as a post-regulator, it creates a way to deliver a clean rail by isolating and reducing supply noise and by decreasing ripples over a wide range of frequencies.
One example of an LDO/switcher solution for noise-sensitive Infotainment systems is the TPS54260-Q1, a 2.5A step-down switching regulator, and the LP5907-Q1, a 250mA low-noise and high-PSRR LDO. The TPS54260-Q1 is used to generate a lower rail voltage from the automotive battery. The LP5907-Q1 is then used to keep the noise down across a wide bandwidth and to reject ripples at various frequencies. The LP5907-Q1 provides a clean rail because of its low noise (10uVrms typical from 10 Hz to 100 kHz) and high PSRR from 1 Hz to 1 MHz (82dB typical at 1 kHz) with high tolerance over load variation. This solution can be used to generate a clean rail such as a 1.8V rail for Bluetooth and GPS and a 3.3V rail for audio codec, gesture sensors, microprocessor and Wi-Fi. Since the LP5907-Q1 doesn’t require a bypassing capacitor for noise reduction, the small solution size of the LP5907-Q1 also simplifies the design process and reduces the total solution size and BOM cost.
LP5907-Q1 PSRR over various load conditions
What noise-sensitive infotainment designs could you use an LDO and switcher solution?