Richpower Technology

SENSORTEK STK3311-X Supply Shortage? LITEON LTR-556ALS-034 LTR-556ALS-039 Pin to Pin Drop-in Replacement Option

If your production line is currently facing an SENSORTEK STK3311-X supply shortage, or your purchasing team is looking for an alternative source for an existing optical sensor design,LITEON LTR-556ALS-034andLTR-556ALS-039are two part numbers worth evaluating as potential replacement options.

The STK3311-X is an integrated ambient light and proximity sensing device from Sensortek. According to available Sensortek documentation, it integrates ambient light sensing, proximity sensing, an IR LED, ADC, timing control and an I²C interface. The device operates from 1.7 V to 3.6 V and uses an 8-pin package measuring approximately 3.94 × 2.36 × 1.35 mm.

For customers considering LITEON alternatives, however, a replacement should not be selected only by comparing the part number or general product category. Package dimensions, pin assignment, optical characteristics, operating voltage, I²C behavior, infrared characteristics, mechanical alignment and software configuration should all be verified before production release.

What Is the SENSORTEK STK3311-X?

The STK3311-X is a combined proximity sensor and ambient light sensor designed for compact electronic products.

Sensortek describes the STK3311-X as an integrated ambient and infrared light-to-digital converter with a built-in IR LED and I²C interface.

Its main functions include:

Ambient light sensing

Proximity sensing

Integrated IR LED

16-bit proximity detection

16-bit ambient light data

Digital I²C interface

Programmable interrupt

Ambient IR noise cancellation

Temperature compensation

Low-power operating modes

1.7 V to 3.6 V operating voltage

-40°C to +85°C operating temperature

8-pin OLGA package

Approximately 3.94 × 2.36 × 1.35 mm package size

Sensortek's current optical-sensor product page also lists the STK3311-X under its proximity + ambient light sensor products, with 16-bit ALS, 16-bit PS, interrupt support and a 1.7–3.6 V supply range.

For engineers maintaining an existing STK3311-X design, these specifications are important when evaluating alternative devices.

Is STK3311-X in Short Supply?

Supply availability for semiconductor components can change by region, quantity, date code, distributor inventory and production status.

Therefore, an STK3311-X supply shortage should be evaluated based on the customer's actual BOM requirement rather than assuming that every distributor has the same availability.

A temporary shortage may result from:

Limited distributor inventory

Allocation

Long lead times

Manufacturer production changes

Regional supply differences

Increased demand

Product lifecycle considerations

Minimum order quantity requirements

Date-code or traceability requirements

For production customers, the more important question is often not simply:

"Can I buy STK3311-X today?" but: "Can I maintain continuous supply for the next production cycle?"

This is where an alternative component strategy can become useful.

LITEON LTR-556ALS-034 and LTR-556ALS-039 as Replacement Candidates

When an STK3311-X design is affected by supply constraints, the LITEON LTR-556ALS-034 and LTR-556ALS-039 can be evaluated as alternative LITEON optical sensor part numbers.

Both part numbers are publicly listed in electronic component distribution and sourcing databases, and LTR-556ALS-034 is identified as a LITEON part number. Public component listings also identify LTR-556ALS-039 within the same LITEON LTR optical-sensor family.

However, engineers should distinguish between:

Replacement candidate and Guaranteed drop-in replacement.

A replacement candidate may perform a similar function but still require PCB, firmware, optical or mechanical changes.

A genuine drop-in replacement requires substantially more verification.

STK3311-X vs LTR-556ALS-034/039

The following table can be used as an initial engineering evaluation framework.

The STK3311-X specifications in the first column are based on available Sensortek documentation. The LITEON specifications should be checked against the latest manufacturer documentation before engineering approval.

Why Consider LTR-556ALS-034 or LTR-556ALS-039?

There are several reasons an engineering or procurement team may investigate LITEON alternatives.

1. Reduce Dependence on a Single Component

If the current product architecture depends entirely on STK3311-X, supply disruption can affect the entire production schedule.

Qualifying an alternative sensor can provide an additional sourcing path.

2. Support Existing Optical Sensor Designs

The LTR series from LITEON includes a broad range of optical sensing products.

This makes LITEON an established manufacturer to consider when evaluating alternatives for ambient-light and optical-sensing applications.

3. Potentially Reduce Redesign Work

If the electrical, mechanical and optical characteristics of the alternative component are sufficiently compatible, the qualification process may be simpler than designing an entirely new sensing architecture.

However, this should be demonstrated through engineering validation rather than assumed from the part number.

4. Improve Supply Flexibility

For high-volume OEM and EMS programs, qualifying more than one source can help purchasing teams manage component availability and production continuity.

Is LTR-556ALS-034 a Drop-in Replacement for STK3311-X?

Not automatically.

The term "drop-in replacement" should be used carefully.

Before replacing STK3311-X with LTR-556ALS-034, engineers should compare:

Package dimensions

Pin assignment

Pin functions

I²C address

I²C register map

Operating voltage

Supply current

ALS resolution

ALS sensitivity

Proximity detection characteristics

IR wavelength

IR LED drive capability

Interrupt behavior

Optical window requirements

PCB footprint

Component height

Software configuration

Temperature characteristics

If any of these parameters differ, the replacement may require PCB or firmware modification.

Therefore, Richpower recommends treating LTR-556ALS-034 as a replacement candidate that requires qualification, rather than automatically describing it as a guaranteed pin-to-pin equivalent.

Is LTR-556ALS-039 a Drop-in Replacement for STK3311-X?

The same principle applies to LTR-556ALS-039.

The part number may be attractive to procurement teams searching for an alternative to STK3311-X, but engineers should confirm the latest LITEON datasheet before approving it for a production BOM.

In particular, compare the mechanical drawing and recommended PCB land pattern with the existing STK3311-X PCB design.

A component that appears similar in size may still have a different optical center, pin assignment or package height.

Important Considerations Before a Drop-in Replacement Pin Compatibility

The first verification should be the pinout.

Check: VDD/GND/SDA/SCL/INT

LED-related pins

NC pins

Any configuration pins

Do not assume that identical pin counts mean identical pin functions.

Package Compatibility

The package should be compared using manufacturer mechanical drawings.

Important dimensions include:

Length

Width

Height

Pin/pad dimensions

Pad pitch

Optical aperture

Optical center

Recommended PCB footprint

Electrical Compatibility

Verify:

Supply voltage

I/O voltage

Maximum current

Standby current

Operating temperature

Logic levels

I²C timing

Optical Compatibility

This is particularly important for optical sensors.

Even if two sensors have similar electrical interfaces, their optical characteristics may differ.

The engineering team should evaluate:

Spectral response

IR wavelength

ALS response

Proximity sensitivity

Ambient IR rejection

Optical crosstalk

Sensor-to-object distance

Cover glass effects

Mechanical enclosure

Firmware Compatibility

A sensor replacement may require firmware modifications.

Compare:

I²C slave address

Register map

Initialization sequence

Interrupt configuration

Gain settings

Integration time

Threshold registers

Proximity configuration

Power-management commands

If the register architecture differs, the replacement cannot be considered software-transparent without additional development.

Recommended STK3311-X Replacement Qualification Process

For OEM, ODM and EMS customers, Richpower recommends a structured replacement evaluation.

Step 1: Confirm the Existing STK3311-X BOM

Collect:

Exact STK3311-X ordering code

Package

PCB footprint

Existing schematic

Firmware revision

Optical/mechanical design

Step 2: Request LTR-556ALS-034 or LTR-556ALS-039 Samples

Obtain samples with traceable manufacturer information.

Step 3: Compare Datasheets

Compare the electrical, mechanical and optical specifications.

Step 4: Verify PCB Compatibility

Check whether the LITEON device can use the existing PCB footprint.

Step 5: Verify Firmware

Confirm I²C address, registers and initialization sequence.

Step 6: Perform Optical Testing

Test under actual product conditions.

For example:

Bright environment

Dark environment

Different display brightness levels

Different cover materials

Different sensor-to-glass distances

Ambient IR interference

Different temperatures

Step 7: Conduct System-Level Validation

The final test should be performed on the actual product rather than only on a laboratory evaluation board.

Step 8: Approve the Alternative BOM

Only after successful qualification should the replacement be added to the production BOM.

LTR-556ALS-034 vs LTR-556ALS-039: Which One Should You Evaluate?

The answer depends on the exact product requirements.

Instead of selecting a part only by availability, procurement and engineering teams should compare:

Package

Optical characteristics

Electrical characteristics

Availability

MOQ

Lead time

Date code

Packaging

Traceability

Price

Production lifecycle

Public sourcing information currently shows both LTR-556ALS-034 and LTR-556ALS-039 in component listings, although inventory information from independent databases should not be treated as a guarantee of current manufacturer availability.

For example, a public netCOMPONENTS listing reported 120,000 units of LTR-556ALS-034 in one supplier listing as of April 21, 2026, while its same page also listed LTR-556ALS-039 among related available part numbers. Actual stock should always be confirmed directly before purchase.

STK3311-X Alternative for Production Procurement

If your purchasing team is searching for:

STK3311-X alternative

STK3311-X replacement

STK3311-X equivalent

or

STK3311-X supply shortage solution

the best approach is to provide the engineering team with several possible replacement candidates and then qualify the selected device.

For procurement teams, Richpower can help evaluate:

LTR-556ALS-034

LTR-556ALS-039

Other LITEON optical sensors

Alternative manufacturer options

Available inventory

Lead time

Packaging

Traceability

Sample requirements

The exact replacement should be determined according to the customer's application and qualification requirements.

Why Source LITEON Components Through Richpower Technology?

Richpower Technology is an electronic component distributor and sourcing company supporting OEM, ODM, EMS and industrial customers.

Our LITEON product portfolio covers multiple optoelectronic categories, including:

Ambient light sensors

Proximity sensors

RGB sensors

Optical sensors

Infrared emitters

Infrared receivers

Photocouplers

LEDs

Other LITEON optoelectronic components

Richpower supports customers with:

Product sourcing

Availability checks

RFQ support

Sample coordination

BOM sourcing

Alternative component evaluation

Supply-chain coordination

For customers experiencing an STK3311-X supply shortage, we can help evaluate LITEON LTR-556ALS-034 and LTR-556ALS-039 as potential alternatives and coordinate the next steps for sample and qualification requirements.

FAQs

What is the STK3311-X?

The STK3311-X is a Sensortek integrated proximity and ambient light sensor with an I²C interface and integrated infrared LED. Sensortek specifies a 1.7–3.6 V operating range and 16-bit ALS and proximity sensing.

What can I use instead of STK3311-X?

LITEON LTR-556ALS-034 and LTR-556ALS-039 can be investigated as replacement candidates. However, engineers should verify pinout, package, optical characteristics, electrical characteristics and software compatibility before production use.

Is LTR-556ALS-034 a drop-in replacement for STK3311-X?

It should not be assumed to be a guaranteed drop-in replacement without qualification. A true drop-in replacement requires verification of mechanical, electrical, optical and software compatibility.

Is LTR-556ALS-039 an alternative to STK3311-X?

LTR-556ALS-039 can be evaluated as a potential alternative for applications currently using STK3311-X. The latest LITEON documentation should be checked before design approval.

What should I check before replacing STK3311-X?

Check pin assignment, package dimensions, PCB footprint, operating voltage, I²C interface, register map, IR wavelength, optical response, interrupt behavior, power consumption and system-level performance.

Does an optical sensor replacement require firmware changes?

It can. If the replacement sensor uses a different register map, I²C address, initialization sequence or interrupt configuration, firmware changes may be required.

Can Richpower provide LTR-556ALS-034 or LTR-556ALS-039?

Richpower Technology can assist customers with LITEON component sourcing, availability checks, quotations and replacement evaluation. Actual stock, lead time and allocation should be confirmed for the specific order quantity and delivery requirement.

Where can I get STK3311-X replacement support?

Contact Richpower Technology with your existing STK3311-X part number, annual quantity, current PCB information and target delivery schedule. Richpower can help evaluate LITEON alternatives and other sourcing options.

About Richpower Technology

Richpower Technology is an electronic component distributor and sourcing company serving customers that require semiconductor, memory, optoelectronic and electronic component supply.

Our product portfolio includes semiconductor components, memory products, LITEON optoelectronic products and other electronic components used in industrial, consumer, computing and embedded applications.

For LITEON products, Richpower supports customers looking for optical sensors, ambient light sensors, proximity sensors, LEDs, photodiodes, photocouplers and related optoelectronic components.

When an existing component becomes difficult to source, Richpower can also support customers in evaluating alternative part numbers based on technical requirements, availability and procurement conditions.

For STK3311-X supply shortage,LTR-556ALS-034 sourcing, orLTR-556ALS-039 sourcing, contact Richpower Technology to discuss your BOM and project requirements.

Conclusion

The SENSORTEK STK3311-X is an integrated ambient light and proximity sensor with an I²C interface, integrated IR LED and low-voltage operation.

When supply continuity becomes a concern,LITEON LTR-556ALS-034 and LTR-556ALS-039 are part numbers that can be considered during an alternative-component evaluation.

However, an alternative optical sensor should not be treated as a confirmed drop-in replacement simply because it belongs to the same general product category. Engineers should verify mechanical dimensions, pin assignment, PCB footprint, electrical specifications, optical performance and firmware compatibility before production approval.

For OEM, ODM, EMS and procurement teams looking for an STK3311-X replacement, Richpower Technology can support LITEON component sourcing, availability checks, quotation requests and replacement evaluation.

Contact Richpower Technology for LTR-556ALS-034, LTR-556ALS-039, STK3311-X replacement requirements and other LITEON optical sensor sourcing needs.