ST adds monolithic automotive DC/DCs
Synchronous buck converters for light-load, low-noise, and isolated applications save space and ease integration
STMicroelectronics has introduced 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 are said to 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 highly integrated monolithic devices need only 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 variants (A6983C) are optimised for light-load operation, with high efficiency and low output ripple, to minimise drain on the vehicle battery in applications that remain active when parked.
The low-noise A6983N variants operate with constant switching frequency and minimise 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. Ideal for use as an isolated gate driver for IGBTs or SiC MOSFETs in traction inverters and on-board chargers (OBCs), this converter allows accurate adjustment of the primary output voltage. 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 synchronisation to an external clock.
The converters are offered in a 3mm x 3mm QFN16 package. Pricing starts at $1.75 for the A6983 and $1.81 for the A6983I, for orders of 1000 pieces, and free samples of the A6983 and A6983I are available from the ST eStore. The STEVAL-A6983CV1 and STEVAL-A6983NV1 A6983 evaluation boards and STEVAL-L6983IV for the A6983I are available to kickstart development and accelerate project completion.
