Monolithic automotive synchronous buck converters 

STMicroelectronics has introduced new automotive-qualified step-down synchronous DC/DC converters that save space and ease integration in applications including body electronics, audio systems, and inverter gate drivers. The A6983 converters offer flexible design choices, comprising six non-isolated step-down converters in low-consumption and low-noise configurations and the A6983I isolated buck converter. With compensation circuitry on-chip, these integrated monolithic devices need minimal external components including filtering, feedback, and a transformer with the A6983I. The non-isolated A6983 converters can supply up to 3A load current and achieve 88% typical efficiency at full load. The low-consumption A6983C variants are optimized for light-load operation, with high efficiency and low output ripple, to minimize drain on the vehicle battery in applications that remain active when parked. The low-noise A6983N variants operate with constant switching frequency and minimize output ripple across the load range for optimum performance in applications such as audio-system power supplies. Both types offer a choice of 3.3V, 5.0V, and adjustable output voltage from 0.85V to VIN. The A6983I is a 10W iso-buck converter with primary-side regulation that eliminates the need for an optocoupler. This converter allows accurate adjustment of the primary output voltage and the transformer turns ratio determines the secondary voltage. All isolated and non-isolated variants have a low quiescent operating current of 25µA and a power-saving shutdown mode that draws less than 2µA. The input-voltage range from 3.5V to 38V, and load-dump tolerance up to 40V, prevent disruption due to transients on the main supply bus. There is also output overvoltage protection, thermal protection, and internal soft start. In addition, optional spread-spectrum operation helps lower electromagnetic interference (EMI) for noise-sensitive applications, and a power-good pin that enables power sequencing. The A6983I and A6983 allow synchronization to an external clock.

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