LDS3985PU28R

PMIC - Voltage Regulators - Linear

The LDS3985PU28R is an adjustable, series linear voltage regulator from Lite-On Semiconductor. It\'s a fixed output, three-terminal regulator that delivers an accurate output voltage from 1.46 V to 22 V, with a guaranteed input voltage of 2.7 V to 24 V. The regulator requires the least amount of external components and the highest reliability, providing up to 1 A of output current capability.

Features and Benefits

• Fixed output voltage range of 1.46 V to 22 V
• Guaranteed input voltage range of 2.7 V to 24 V
• Up to 1 A of output current capability
• Operating temperature range of -40°C to 125°C
• Voltage accuracy of ±2%
• Low dropout voltage
• Adjustable current limiting from 1 mA to 1 A
• Low output voltage ripple
• Low input current draw
• Under-voltage lockout and short-circuit protection
• Operating Efficiency > 90%

Applications

The LDS3985PU28R voltage regulator is intended for use in computing, cellular phone, instrumentation, and automotive applications. It\'s a great choice for system circuit boards where an adjustable output voltage is desired in a compact and lightweight form factor. Some potential applications include:

• Computer peripherals
• MP3 players, digital cameras and video cameras
• Smartphones and PDA devices
• LED strips and arrays
• Lighting ballast and driver boards
• Cable and DMX lighting
• Tablet computers
• Automotive electronics

Working Principle

The LDS3985PU28R voltage regulator contains a P-channel MOSFET which operates as a series-pass device along with error amplifier, under-voltage lock-out, reference and current limit circuitry. The output voltage is adjustable by means of an external voltage divider. The voltage divider comprises a resistor from the device’s output to its adjust pin along with a resistor from the adjust pin to ground. The ratio of the two resistors sets the output voltage of the regulator.

When the voltage on the output pin rises, this voltage is fed back to the error amplifier which is configured as an ‘inverting amplifier’. When the output voltage becomes greater than the set point of the regulator, the error amplifier turns the P-channel MOSFET off, preventing the output voltage from rising further. When the voltage on the output dips, the error amplifier responds by turning the P-channel MOSFET on, reducing the voltage at the output pin.

An under-voltage lock-out circuit requires a minimum input voltage of 2.7 V to ensure proper regulation. The under-voltage lock-out circuit also provides short-circuit protection by turning the P-channel MOSFET off when the output voltage drops below a predetermined percentage of the set point. The current limiting circuit monitors the voltage drop across the R SET resistor and cuts off the P-channel MOSFET when the current exceeds 1 A. This simple and efficient design ensures accurate regulation with excellent line and load regulation.

Conclusion

The LDS3985PU28R linear regulator from Lite-On provides an adjustable output voltage from 1.46 V to 22 V with a guaranteed input voltage of 2.7 V to 24 V and up to 1 A of output current. With an operating temperature range of -40°C to 125°C and a voltage accuracy of ±2%, it is the ideal choice for a compact, low dropout voltage regulator for computing, cellular phone, instrumentation and automotive applications. The device is also protected against over-voltage, under-voltage and short-circuit, making it an ideal choice for systems requiring high reliability.