LP2985ITPX-2.9/NOPB

LP2985ITPX-2.9/NOPB Application Field and Working Principle

From PMIC - Voltage Regulators - Linear category, LP2985ITPX-2.9/NOPB is a low-dropout linear regulator, usually called as LDO, produced by Texas Instruments. This LDO is a single-channel, fixed output voltage regulator designed to supply up to 250 mA output current to various applications and systems at voltages as low as 1.8V. The output voltage accuracy of this device is ±2.5%.

Application Field

LP2985ITPX-2.9/NOPB can be commonly found in battery-powered applications, since its quiescent current draw is very low. In addition, this device can also be used as a low-noise voltage regulator, enabling it to be used in communication interface and RF-signal conditioning applications. Other applications include power-management and transceiver biasing, where low-dropout voltage and accurate voltage regulation is needed. Furthermore, its output voltage is adjustable within ±8%. For example, it can be used for powering radio transceivers in systems like WLAN, Bluetooth, and Zigbee.

Working Principle

LP2985ITPX-2.9/NOPB consists of a p-channel MOSFET pass element, error amplifier, internal voltage reference, peak current-limit circuit, thermal-limit-protection circuit and an output Voltage Divider. In the device, the voltage to be regulated is applied externally to the R1-R2 divider. The output of the R1-R2 divider is applied as the reference input to the error amplifier, this input is compared to an internal 1.25V reference voltage and feedback loop is formed. If the output voltage is increased, the error amplifier output is driven to negative potential and the gate of the pass element is pulled toward the negative, reducing current through the load, which reduces the output voltage. If the output voltage is decreased, the error amplifier output is increased to the positive potential, driving the gate of the pass element to higher potential, allowing more current to gush into the load, thus increasing the output voltage. This process continues until the output voltage is equal to the set value.

The peak current-limit circuit prevents the pass device from exceeding the rated current value. The thermal-limit-protection circuit limits the maximum power dissipation of the device by sensing its junction temperature. The output voltage of the device is externally adjustable without compromising the device accuracy.

The wide input voltage of this LP2985ITPX-2.9/NOPB device is 9V to 15V, and its input bypass capacitor must be placed close to the VIN pin to avoid large voltage transients.

The LP2985ITPX-2.9/NOPB is available in thermally enhanced 8-pin MSOP package.