AS1356-18-T

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators Overview

The AS1356-18-T is a fixed-voltage linear low-dropout regulator (LDO) with an 1.8V output, manufactured by ams OSRAM USA INC. It delivers up to 150mA of output current and operates within an input voltage range of 2.5V to 5.5V. The device features ultra-low dropout voltage, high power-supply rejection ratio (PSRR), and integrated over-temperature and over-current protection. A unique Power-OK (POK) pin provides active-low open-drain monitoring for out-of-regulation conditions. It utilizes a P-channel MOSFET pass transistor and includes reverse-battery protection. The component is housed in a 5-pin SOT23 package and supports operation across a temperature range of -40°C to +85°C.

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators Feature Summary

• Integrated Power-OK circuitry providing active-low open-drain output to monitor regulation status
• P-channel MOSFET pass transistor enabling low quiescent current and minimal dropout voltage
• Built-in reverse-battery protection disconnecting internal circuitry upon incorrect polarity connection
• Comprehensive protection against thermal overload and output short-circuit conditions

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators Applications

• Powering microprocessors in handheld devices
• Battery-powered consumer electronics such as mobile phones and digital cameras
• Portable media players including MP3 and CD/DVD players
• Personal Digital Assistants (PDAs) and handheld computers

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators Procurement Notes

Verify the specific ordering suffix and manufacturer part number against official distributor catalogs to ensure compatibility with the required 1.8V fixed output and Power-OK functionality. Confirm that the procurement source sources directly from authorized channels to guarantee authenticity, as counterfeit components may lack critical safety features like reverse-battery protection or exhibit degraded thermal performance. Cross-reference the datasheet revision to ensure all electrical characteristics align with system design requirements.

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators Selection Notes

Select this component when a fixed 1.8V supply is required for sensitive logic circuits in battery-operated systems. The inclusion of the Power-OK feature makes it suitable for applications requiring precise power-on-reset sequencing or continuous voltage monitoring. Ensure the load current does not exceed 150mA and that the input voltage remains within the 2.5V to 5.5V range. Consider the thermal dissipation capabilities of the PCB layout, as the ground pin serves as a heat sink, to maintain junction temperatures within safe operating limits under maximum load conditions.

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators Part Context

The AS1356 series belongs to a family of high-performance, fixed-voltage linear LDOs designed for low-noise and low-power applications. It shares core architectural similarities with the AS1353 but adds the distinct Power-OK monitoring capability. Both variants utilize a P-channel MOSFET pass element to achieve superior dropout performance compared to traditional NPN-based regulators. The series is optimized for use with small ceramic capacitors, simplifying board space requirements while maintaining stability across varying load and line conditions.

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators Replacement Considerations

AS1353-18-T: Identical electrical specifications except for the absence of the Power-OK pin; requires pin 4 (BP) to be left unconnected or bypassed if noise reduction is needed.

Voltage Regulators - Linear, Low Drop Out (LDO) Regulators FAQ

How does the Power-OK (POK) pin indicate an out-of-regulation condition?

The POK pin is an active-low, open-drain output that goes low when the output voltage falls below approximately 92% to 97% of its nominal value, indicating dropout, current limit, or thermal shutdown.

What is the function of the BP pin on the AS1356?

The BP pin is not present on the AS1356; it is exclusive to the AS1353 variant for reference-noise bypass using a 0.01µF capacitor. On the AS1356, Pin 4 is the POK output.

Can the AS1356-18-T withstand indefinite short-circuit conditions?

Yes, the device includes current limiting circuitry that protects the P-channel MOSFET output, allowing it to be shorted to ground indefinitely without damage.