Semiconductors and Components

Linear Regulator Has Extended SOA

10 February 2016

The LT3089 from Linear Technology Corp. is an 800 mA wide input voltage range linear regulator with key usability, monitoring and protection features. The device has an extended safe operating area (SOA) compared to existing regulators, suiting it for high input/­output voltage and high output current applications where older regulators limit the output.

Linear Technology LT3089 linear regulator (Source: Linear Technology).Linear Technology LT3089 linear regulator (Source: Linear Technology).

The LT3089 uses a current source reference for single resistor output voltage settings and output adjustability down to 0 V. Output current limit can be set externally with a single resistor. This regulator architecture, combined with low millivolt line and load regulation, enables multiple ICs to be paralleled easily for heat spreading and higher output current. The current from the device’s current monitor can be summed with the set current for line ­drop compensation, where the output of the LT3089 increases its current to compensate for line drops.

Line and load regulation is under 2 mV, independent of output voltage, and input voltage ranges from 1.2 V to 36 V. The device fits well in applications requiring multiple rails. Output voltage is programmable with a single resistor from 0 V to 34.5 V with a 1.2 V dropout. The on­-chip trimmed 50 µA current reference is ±1 percent accurate. The regulation, transient response and output noise (27 µV) are independent of output voltage due to the device’s voltage follower architecture.

The LT3089 is configurable as a two-­terminal current source using only two resistors. Input or output capacitors for stability are optional in either linear regulator mode or current source mode of operation. The LT3089 provides several monitoring and protection functions. Current limit can be programmed with a single resistor. Monitor outputs provide a current output proportional to temperature (1µA/°C) and output current (200 µA/A), allowing easy ground-­based measurement. The current monitor can be used to compensate for cable drops.

Internal protection circuitry includes reverse input protection, reverse ­current protection, internal current limiting and thermal shutdown.

The LT3089 comes in various thermally enhanced surface mount compatible packages, including a low profile (0.75 mm) 12-­lead, 4 mm x 4 mm DFN, a 16-­lead thermally enhanced TSSOP, and a 7-­lead DD­Pak. All dissipate 2 W in surface mount applications with no heat sink. Various combinations of grades/temperature ranges are offered including: E and I grades ­40 °C to 125 °C, H grade ­40 °C to 150 °C, and the high reliability MP grade ­55 °C to 150 °C.

1,000-piece pricing starts at $2.13 each for the E grade.

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