Demonstration circuit 2624A features the LT3094, an ultralow noise, ultrahigh power supply rejection ratio (PSRR) negative low dropout (LDO) regulator. DC2624A operates over an input range of –3.8V to –20V, and can deliver up to 500mA output current. It features ultralow noise (0.8µVRMS from 10Hz to 100kHz) and very high PSRR (75dB at 1MHz).
The LT3094 enable function (EN/UVLO pin) is bidirectional and can be controlled with either a positive or a negative voltage. The LT3094 also offers programmable current limit functionality by connecting a resistor from ILIM to GND. Current monitoring is also achieved by sensing the ILIM pin voltage. The VIOC tracking function controls an upstream switching converter to maintain a constant voltage across the regulator and, hence, minimize power dissipation. The power good feedback (PGFB) pin is used to set a programmable power good threshold, and activates the fast start-up circuitry. To use the power good function, connect an external voltage source at VEXT. If power good and fast start-up functionality are not needed, tie PGFB to IN.
Built-in protection includes reverse battery protection, reverse current protection, internal current limit with foldback, and thermal limit with hysteresis.
The LT3094 data sheet gives a complete description of the part, operation and applications information. The data sheet must be read in conjunction with this demo manual for demonstration circuit DC2624A. The LT3094 is assembled in 12-lead MSOP and 3mm × 3mm DFN packages with an exposed pad on the bottom-side of the IC. Proper board layout is essential for maximum thermal performance.