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Automotive & Transportation

Step-Down Regulator Handles Inverting Outputs

12 April 2016

The LTC7149 from Linear Technology is a 60 V, 4 A synchronous buck regulator for negative output voltage supplies. It incorporates a current mode architecture with user selectable internal or external loop compensation and an output voltage that is programmed with a single external resistor.

Linear Technology’s LTC7149 synchronous buck regulator: Source: LinearLinear Technology’s LTC7149 synchronous buck regulator: Source: LinearThe LTC7149 operates from an input voltage range of 3.4 V to 60 V and provides an adjustable output voltage from 0 V to -28 V, while delivering up to 4 A of continuous output current. Its wide input and output voltage ranges suit it for a wide range of test, measurement and industrial applications.

The part incorporates an internally generated 50µA current source on the ISET pin that enables it to deliver outputs as low as -28 V with the use of a single external programming resistor. Furthermore, the LTC7149 offers ±0.8% output voltage accuracy. Its switching frequency is user programmable from 300 kHz to 3 MHz, enabling the use of tiny, low cost capacitors and inductors.

The LTC7149 uses internal switches with RDS (ON) of only 110 milliohms and 50 milliohms to deliver efficiencies as high as 92%. Burst Mode® operation offers high efficiency at light loads, requiring only 440 µA of quiescent current. For noise sensitive applications, the LTC7149 can run in forced continuous mode, offering very low output ripple. It also includes ground-referenced clock and PGOOD pins, eliminating the need for level shifters. Additional features include a power good voltage monitor, programmable wire drop compensation, external synchronization capability and thermal protection.

The LTC7149EUFD is available in a 4 mm x 5 mm QFN-28, and the LTC7149EFE is offered in a 28-lead, thermally enhanced TSSOP package. Industrial grade versions, the LTC7149IUFD and LTC7149IFE, are guaranteed to operate over the -40 °C to 125 °C operating junction temperature range. Pricing starts at $5.65 each in 1,000-piece quantities. All versions are available from stock.



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