Fixed and Adjustable LDO Regulators

Ultra-LDO

LDOs are a special subset of linear regulators. The drop out is the minimum voltage across the regulator (input – output differential) to maintain regulation. An LDO achieves low power dissipation by allowing a lower input voltage to be used for a given output voltage compared to what a standard linear regulator would need to maintain regulation.

Ultra-Low Drop-Out voltage regulators (ULDOs) achieve a typical dropout voltage below 200mV at full load.

Low Noise/High PSRR

The Power Supply Rejection Ratio (or Supply Voltage Rejection, SVR) measures how well an LDO rejects the ripple coming from the input at various frequencies. The PSRR is expressed in dB and it is measured as the ratio between the ripple on the input voltage and the ripple on the output voltage. LD59015 and LD39115 series of high PSRR LDOs from STMicroelectronics are specifically designed to improve this critical parameter in noise sensitive, RF and battery powered wireless applications.

Unlike PSRR, the output noise in an LDO is generated internally within the circuitry of the voltage regulator. Measured as a function of frequency (in µV/sqrt[Hz]) or alternatively as output noise voltage (in µVRMS over a range of frequency), noise is a critical parameter in RF and wireless applications. An optimized low-noise LDO design, like STMicroelectronics LDLN015, delivers an impressive low 6.3µVRMS output noise voltage from 10Hz to 100KHz.

Low Quiescent Current

The quiescent current of an LDO is the current drawn from the input pin to power the internal circuitry when the LDO is regulating. This is different from the shutdown current which is measured when the LDO is off. The quiescent current is usually negligeable at full load, because it is several orders of magnitude smaller than the output current. It becomes a critical parameter at quasi-zero or very light load, to prolong battery life in applications with long standby time. A common issue is the trade off between low quiescent current and dynamic performance (load transient response and PSRR). STMicroelectronics STLQ015 achieves a fast load transient despite the extremely low quiescent current (1µA).

Tiny Package

The ultra-small, high performance LDOs by STMicroelectronics are particularly suitable for the latest generation portable devices (tablets, smartphones, portable healthcare and fitness) where board space real estate is major constraint.

• Chip-Scale-Package (Flip-Chip) 0.5 and 0.4mm pitch: 1x1mm, 0.8x0.8mm, 0.69x0.69mm
• Dual-in-line Flat Non-leaded (DFN): 3x3mm, 2x2mm, 1.2x1.3mm
• SOT666: 1.6x1.6mm