LM3557SD-2 LED Driver IC Equivalent & Substitute Parts

Part Overview

The LM3557SD-2 is an LED driver regulator IC manufactured by Texas Instruments, designed for backlight applications with an integrated 800mA switch and step-up (boost) topology. This device operates across a 2.7V to 7.5V supply range at 1.2MHz switching frequency within an 8-WSON (3x3) package.

The LM3557SD-2 is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production or maintenance requirements for systems utilizing this component.

Substiute Parts

LM3557SD-2

Texas InstrumentsIn Stock: 3828LM3557SD-2 Datasheet

Current PartRFQ

AL3050FDC-7

Diodes IncorporatedIn Stock: 7472AL3050FDC-7 Datasheet

MFR RecommendedRFQ

AP3602AKTR-G1

Diodes IncorporatedIn Stock: 1415AP3602AKTR-G1 Datasheet

MFR RecommendedRFQ

LT3519EMS-2#PBF

Analog Devices Inc.In Stock: 1442LT3519EMS-2#PBF Datasheet

MFR RecommendedRFQ

LT3954IUHE#TRPBF

Analog Devices Inc.In Stock: 3200LT3954IUHE#TRPBF Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the LM3557SD-2 are identified based on the following critical parameters that determine functional compatibility:

Primary Substitution Criteria:

• Topology: Step-Up (Boost) converter architecture
• Internal Switch: Presence of integrated switching element
• Number of Outputs: Single output configuration
• Supply Voltage Range: Minimum 2.7V input capability
• Current Handling: Switch current capacity of 750mA or greater
• Switching Frequency: Operation in the 750kHz to 2.2MHz range
• Package Type: Surface mount with exposed pad construction
• Operating Temperature: -40°C to 85°C minimum range
• Applications: LED driver and backlight functionality

The four substitute parts listed below meet these core criteria while offering varying levels of feature enhancement, package options, and compliance certifications. Each substitute maintains the essential boost converter topology and LED driver functionality required for backlight applications.

Parameter Comparison

Engineering Selection Recommendations

LT3954IUHE#TRPBF (Analog Devices Inc.)

This part offers the highest current capacity at 5A switch current and supports the widest supply voltage range (4.5V to 40V). It features multiple topology options including boost, buck, SEPIC, and flyback configurations, providing maximum design flexibility. The device is active and ROHS3 compliant with an extended operating temperature range to 125°C. The 36-QFN package is significantly larger than the original LM3557SD-2, requiring PCB layout modifications. This substitute is suitable for applications requiring higher power delivery or multi-topology capability.

LT3519EMS-2#PBF (Analog Devices Inc.)

This part maintains 750mA switch current, closely matching the original 800mA specification. It supports a 3V to 30V supply range and offers both analog and PWM dimming options. The device is active and ROHS3 compliant with extended temperature operation to 125°C. The 16-MSOP package is larger than the original 8-WSON, requiring PCB redesign. This substitute is appropriate for applications requiring extended supply voltage range or advanced dimming control.

AP3602AKTR-G1 (Diodes Incorporated)

This part operates at the same 1.2MHz switching frequency as the original LM3557SD-2 and maintains identical supply voltage minimums (2.7V). However, it provides only 100mA output current and limits supply voltage to 5V maximum. The device is active and ROHS3 compliant. The SOT-23-6 package is significantly smaller, offering potential PCB space savings. This substitute is suitable only for lower-power backlight or camera flash applications where 100mA current is sufficient.

AL3050FDC-7 (Diodes Incorporated)

This part operates at 750kHz with 40mA output current, representing a significant reduction from the original 800mA specification. It supports a 2.7V to 5.5V supply range and includes PWM dimming capability. The device is obsolete but ROHS3 compliant. The 6-UDFN package is the smallest option. This substitute is suitable only for minimal-power LED driver applications and is not recommended for designs requiring the full 800mA capacity of the original part.

Frequently Asked Questions (FAQ)

Q: Can the LT3954IUHE#TRPBF directly replace the LM3557SD-2 without circuit modifications?

A: No. While both are boost converters with integrated switches, the LT3954IUHE#TRPBF has a significantly different package (36-QFN versus 8-WSON), higher current capacity (5A versus 800mA), and wider supply voltage range (4.5V-40V versus 2.7V-7.5V). PCB layout redesign and potential circuit topology adjustments are required.

Q: Which substitute part most closely matches the original LM3557SD-2 specifications?

A: The LT3519EMS-2#PBF provides the closest current specification at 750mA (versus 800mA) and maintains boost topology functionality. However, it requires package redesign due to the 16-MSOP footprint difference.

Q: Is the AP3602AKTR-G1 suitable for all applications using the LM3557SD-2?

A: No. The AP3602AKTR-G1 is limited to 100mA output current and 5V maximum supply voltage. It is suitable only for lower-power backlight or camera flash applications. Applications requiring the full 800mA capacity cannot use this substitute.

Q: What is the impact of the AL3050FDC-7's 40mA current rating compared to the original 800mA?

A: The AL3050FDC-7 provides only 5% of the original current capacity. This substitute is applicable only to minimal-power LED driver designs and is not suitable for designs requiring the full output current of the LM3557SD-2.

Q: Are all substitute parts RoHS compliant?

A: The LT3954IUHE#TRPBF, LT3519EMS-2#PBF, AP3602AKTR-G1, and AL3050FDC-7 are all ROHS3 compliant. The original LM3557SD-2 is RoHS non-compliant. Designs requiring RoHS compliance must transition to one of the substitute parts.

Q: What are the package considerations when selecting a substitute?

A: The original LM3557SD-2 uses an 8-WSON (3x3) package. Substitutes use different packages: LT3954IUHE#TRPBF (36-QFN), LT3519EMS-2#PBF (16-MSOP), AP3602AKTR-G1 (SOT-23-6), and AL3050FDC-7 (6-UDFN). Each requires distinct PCB footprint design and layout modifications.

Q: Can the LM3557SD-2 be used interchangeably with these substitutes in existing designs?

A: No. Each substitute has different electrical specifications, package footprints, and pin configurations. Direct interchangeability is not possible. Circuit redesign and validation are required for any substitution.