L4931 3.3V out 250mA out TO-92-3 Linear Voltage regulator

Description

Low-dropout (LDO) regulators work similarly as all linear voltage regulators. The main difference between LDO and non-LDO regulators is their schematic topology. Instead of an emitter follower topology, low-dropout regulators use an open collector or open drain topology. In this topology, the transistor may be easily driven into saturation with the voltages available to the regulator. This allows the voltage drop from the unregulated voltage to the regulated voltage as low as the saturation voltage across the transistor.

Features:

• Very low dropout voltage (0.4V)
• Shallow quiescent current
• Typical 50µA in OFF mode and 600µA in ON mode
• Output current up to 250mA
• Logic controlled electronic shutdown
• Internal current and thermal limit
• Only 2.2µF for stability
• Supply voltage rejection of 70 dB typical for 5V version

Package included: 1x L4931 3.3V out 250mA out TO-92-3 Linear Voltage regulator

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Development  Resources: demo codes, schematics, datasheets, etc

For the circuit given in the figure to the right, the output voltage is given as:

If a bipolar transistor is used, as opposed to a field-effect transistor or JFET, significant additional power may be lost to control it. In contrast, non-LDO regulators take that power from the voltage drop itself. There will be significant power loss in the control circuit for high voltages under meagre In-Out difference.

Because the power control element functions as an inverter, another inverting amplifier is required to control it, which increases schematic complexity compared to a simple linear regulator.

Power FETs may be preferable to reduce power consumption, but this poses problems when the regulator is used for low input voltage. FETs usually require 5 to 10 V to close completely. Power FETs may also increase the cost.

Voltage regulator

The L4931 3.3V out 250mA out TO-92-3 Linear Voltage regulator is a very low drop Voltage Regulator with inhibit function. The very low drop voltage (0.4V) and the shallow quiescent current make it particularly suitable for low noise, low power applications and especially in battery-powered systems. A TTL compatible shutdown logic control function is available in PPAK and SO-8 packages. This means that when the device is used as a local regulator, a part of the board can be put in standby mode, decreasing the total power consumption. It requires only a 2.2µF capacitor for stability allowing space.

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Notes:

1. There may be slight size deviations due to manual measurement, different measuring methods and tools.
2. The picture may not reflect the actual colour of the item because of different photographing light, angles and display monitors.