DESCRIPTION

The LT3086 is a multi-feature, low dropout, low noise 2.1A linear regulator that operates over a 1.4V to 40V input supply range. Dropout voltage at 2.1A is typically 330mV. One resistor sets output voltage from 0.4V to 32V. Output voltage tolerance is guaranteed to ±2% over line, load and temperature. The LT3086 is stable with ceramic output capacitors, requiring a minimum of 10µF.

The LT3086’s programmable cable drop compensation cancels output voltage errors caused by resistive connections to the load. A master/slave configuration allows paralleling of multiple devices for higher load current and heat spreading without external ballast resistor requirements. Output current and temperature monitoring along with a power good flag provide system diagnostic and debug capability. Internal fault circuitry includes thermal shutdown and current limit with foldback. Thermal limit and current limit are also externally programmable.

Packages include the thermally enhanced 16-lead (5mm × 4mm) DFN, 16-lead TSSOP, 7-lead DD-Pak and 7-lead TO-220.

 

INFORMATIONS SUR LES APPLICATIONS

The LT3086 is a multifunction, low dropout, low noise, linear regulator with shutdown, and adjustable power good. The device supplies 2.1A with a typical dropout voltage of 330mV and operates over a wide 1.4V to 40V input supply range.

The operating quiescent currentis 1.2mAanddrops to less than 1µA in shutdown. The LT3086 regulator optimizes stability and transient response with a minimum low ESR 10µF ceramic output capacitor. A single resistor sets the output voltage from 0.4V to 32V. Similarly, a single resistor sets the power good threshold. The regulator typically provides 0.1% line regulation and 0.1% load regulation.

The LT3086 has convenient programmable diagnostic features. An output current monitor, that is typically 1/1000 of the output current, can set the current limit lower than the typical 2.4A internal limit. A temperature monitor, that is typically 10mV/°C where 250mV = 25°C,  can set the thermal limit lower than the typical 165°C internal thermal limit.

For applications where the voltage error at the load is caused by the resistance in the connections between the LT3086 and the load, programmable cable drop compensation cancels the error with a single resistor. Multiple LT3086 regulators can be paralleled for higher load currents and heat spreading without the need for external ballast resistors.

During load transients where the output overshoots (regulated output voltages of 0.8V or higher), an internal pull-down current activates pulling about 15mA from the OUT pin to ground.

The pull-down current is disabled when the output is at or below regulation. The regulator and the output overshoot pull-down turn off when the output voltage is pulled higher than the input by typically 225mV. Curves of OUT Over IN Shutdown Threshold appear in the Typical Performance Characteristics section.

Internal protection circuitry includes reverse-battery protection, reverse-out put protection, reverse-current protection, current limit with foldback and thermal shutdown.

 

Programming Power Good

The adjustable power good threshold is programmed with a single resistor, RPGSET, similar to how the output voltage is programmed by RSET. Similar to the SET pin, RPWRGD determines the power good threshold with the combination of a 0.4V reference voltage and a precision 50µA pull-down current. The power good signal pulls high if the voltage on RPWRGD increases above 0.4V. Built-in hysteresis of typically 0.6% exist for both the 0.4V voltage threshold and the 50µA current source. Connecting a resistor between the RPWRGD and PWRGD pins can increase the power good hysteresis..The PWRGD pin is the power good open-collector logic output. An internal delay of typically 17µs exists only for the rising edge (when the regulator output voltage rises above the power good threshold) to reject noise or chatter during startup. If the power good function is not needed, leave the RPWRGD and PWRGD pins floating.