RT8471ZSP LED Driver IC Equivalent & Substitute Parts

Part Overview

The RT8471ZSP is a discontinued LED Driver IC manufactured by Richtek USA Inc., designed for step-down (buck) topology DC-DC regulation with 1.2A output capability. This automotive-grade component integrates an internal switch and supports both analog and PWM dimming for lighting and signage applications. Due to its discontinued status at DiGi Electronics, equivalent substitute parts are necessary to maintain design continuity and ensure supply chain availability for new production runs and legacy system support.

Key Parameters

Parameter	RT8471ZSP Value
Manufacturer	Richtek USA Inc.
Category	Power Management (PMIC)
Type	DC DC Regulator
Topology	Step-Down (Buck)
Internal Switch	Yes
Number of Outputs	1
Voltage Supply Range	7V to 36V
Current Output / Channel	1.2A
Dimming Capability	Analog, PWM
Operating Temperature	-40°C to 125°C (TJ)
Grade	Automotive
Package / Case	8-SOIC (0.154", 3.90mm Width) Exposed Pad
RoHS Status	ROHS3 Compliant
MSL Rating	3 (168 Hours)
Product Status	Discontinued at DiGi Electronics

Substitute Part Grouping Explanation

Substitute parts for the RT8471ZSP are selected based on strict alignment with the following critical parameters:

Primary Substitution Criteria:

Topology: Step-Down (Buck) configuration with internal switch
Output Configuration: Single output, LED driver application
Dimming Support: Analog and/or PWM dimming capability
Supply Voltage Range: Minimum 6V to 7V; Maximum 36V or higher
Output Current: 1.2A or greater per channel
Operating Temperature: -40°C to 125°C or wider range
Automotive Grade: Preferred for consistency
RoHS3 Compliance: Required for regulatory alignment
Package Compatibility: Surface mount with exposed pad preferred

Substitutes are grouped into two categories:

Category A - Direct Topology Match (Step-Down Buck): Parts maintaining identical step-down buck topology with comparable current ratings and voltage ranges. These provide the closest functional equivalence.

Category B - Alternative Topology (Step-Up Boost / SEPIC): Parts with different topologies but compatible dimming, current, and voltage characteristics. These require circuit redesign validation but offer functional LED driver capability.

Parameter Comparison

Part Number	Manufacturer	Topology	Supply Voltage (Min-Max)	Output Current	Dimming	Operating Temp	Package	Status	Grade
RT8471ZSP	Richtek USA Inc.	Step-Down (Buck)	7V - 36V	1.2A	Analog, PWM	-40°C to 125°C	8-SOIC-EP	Discontinued	Automotive
IS31LT3360-SDLS4-TR	Lumissil Microsystems	Step-Down (Buck)	6V - 40V	1.2A (Switch)	Analog, PWM	-40°C to 125°C	SOT-89-5	Active	Automotive
LED2000PUR	STMicroelectronics	Step-Down (Buck)	3V - 18V	3A	PWM	-40°C to 150°C	8-VFQFPN (4x4)	Active	Not Specified
LED6000PHR	STMicroelectronics	Step-Down (Buck)	4.5V - 61V	3A	PWM	-40°C to 150°C	16-HTSSOP	Active	Not Specified
LM3406MHX/NOPB	Texas Instruments	Step-Down (Buck)	6V - 42V	1.5A	PWM	-40°C to 125°C	14-HTSSOP	Active	Automotive
LM3530UMX-25A/NOPB	Texas Instruments	Step-Up (Boost)	2.7V - 5.5V	30mA	PWM	-40°C to 85°C	12-DSBGA	Active	Not Specified
LT3519IMS-2#PBF	Analog Devices Inc.	SEPIC, Step-Down (Buck), Step-Up (Boost)	3V - 30V	750mA (Switch)	Analog, PWM	-40°C to 125°C	16-MSOP	Active	Not Specified
MAX1561ETA+T	Analog Devices Inc./Maxim Integrated	Step-Up (Boost)	2.6V - 5.5V	950mA (Switch)	Analog, PWM	-40°C to 85°C	8-TDFN (3x3)	Active	Not Specified
MAX20051AUD/V+T	Analog Devices Inc./Maxim Integrated	Step-Down (Buck)	4.5V - 65V	2A	Analog, PWM	-40°C to 125°C	14-TSSOP-EP	Active	Not Specified
MCP1664T-E/OT	Microchip Technology	Step-Up (Boost)	2.4V - 5.5V	300mA	PWM	-40°C to 125°C	SOT-23-5	Active	Not Specified
MIC3287-24YD6-TR	Microchip Technology	Step-Up (Boost)	2.8V - 6.5V	350mA (Switch)	Analog, PWM	-40°C to 125°C	TSOT-23-6	Active	Not Specified

Engineering Selection Recommendations

Tier 1 - Recommended Direct Substitutes (Step-Down Buck Topology):

IS31LT3360-SDLS4-TR (Lumissil Microsystems) provides the closest functional match to RT8471ZSP. It maintains step-down buck topology, identical 1.2A output current, overlapping supply voltage range (6V-40V), dual dimming support (Analog and PWM), automotive grade certification, and active product status. Package differs (SOT-89-5 vs. 8-SOIC-EP), requiring PCB layout modification. RoHS3 compliant and MSL 3 rated.

LM3406MHX/NOPB (Texas Instruments) offers step-down buck topology with 1.5A output current, supply range 6V-42V, PWM dimming, automotive grade, and active status. Operating temperature matches (-40°C to 125°C). Package is 14-HTSSOP, requiring significant layout redesign. RoHS3 compliant and MSL 1 rated (superior moisture performance).

MAX20051AUD/V+T (Analog Devices Inc./Maxim Integrated) delivers step-down buck topology with 2A output current (exceeds 1.2A requirement), supply range 4.5V-65V, dual dimming support (Analog and PWM), and active status. Operating temperature matches. Package is 14-TSSOP-EP with exposed pad. RoHS3 compliant and MSL 1 rated.

Tier 2 - Alternative Topology Substitutes (Requires Circuit Validation):

LED2000PUR and LED6000PHR (STMicroelectronics) maintain step-down buck topology with higher output current (3A) and extended operating temperature (-40°C to 150°C). LED6000PHR supports wider supply voltage (4.5V-61V). Both are active products and RoHS3 compliant. Package changes require layout redesign. Suitable for applications requiring higher current capacity or extended temperature range.

LT3519IMS-2#PBF (Analog Devices Inc.) offers multi-topology capability (SEPIC, Step-Down, Step-Up) with 750mA output current, supply range 3V-30V, dual dimming support, and active status. Topology flexibility enables diverse circuit configurations. 16-MSOP package requires significant redesign. RoHS3 compliant and MSL 1 rated.

Tier 3 - Limited Compatibility (Step-Up Boost Topology):

LM3530UMX-25A/NOPB, MAX1561ETA+T, MCP1664T-E/OT, and MIC3287-24YD6-TR employ step-up (boost) topology, fundamentally different from the original step-down architecture. These are suitable only for applications where input voltage is lower than required output voltage. Output current ratings (30mA to 950mA) are generally lower than RT8471ZSP. Supply voltage ranges are restricted (2.4V-6.5V). These require complete circuit redesign and are not direct substitutes.

Compliance & Certification Summary:

All substitute parts maintain RoHS3 compliance and REACH unaffected status, consistent with RT8471ZSP. Automotive-grade parts (IS31LT3360-SDLS4-TR, LM3406MHX/NOPB) are preferred for automotive applications. MSL ratings vary; MSL 1 parts (LM3406MHX/NOPB, MAX20051AUD/V+T, LT3519IMS-2#PBF, MAX1561ETA+T, MCP1664T-E/OT, MIC3287-24YD6-TR) offer superior moisture resistance compared to MSL 3 (RT8471ZSP, IS31LT3360-SDLS4-TR, LED6000PHR).

Frequently Asked Questions (FAQ)

Q: Can IS31LT3360-SDLS4-TR directly replace RT8471ZSP without circuit modification?

A: IS31LT3360-SDLS4-TR maintains identical topology, current rating, and dimming capability. However, the package differs (SOT-89-5 vs. 8-SOIC-EP), requiring PCB footprint redesign. Electrical functionality is compatible; physical layout changes are mandatory.

Q: Why are step-up (boost) topology parts listed if the original is step-down (buck)?

A: Step-up parts are included for applications where input voltage is lower than required output voltage. These represent alternative solutions for specific use cases but require complete circuit redesign and are not direct substitutes for step-down applications.

Q: What is the significance of the MSL (Moisture Sensitivity Level) rating difference?

A: RT8471ZSP is MSL 3 (168 hours), meaning it requires controlled storage and handling. Substitute parts with MSL 1 (unlimited) offer superior moisture resistance and reduce storage/handling complexity. MSL 3 parts require equivalent precautions.

Q: Does LM3406MHX/NOPB support analog dimming like RT8471ZSP?

A: LM3406MHX/NOPB supports PWM dimming only. RT8471ZSP supports both analog and PWM dimming. If analog dimming is required, select IS31LT3360-SDLS4-TR, MAX20051AUD/V+T, or LT3519IMS-2#PBF instead.

Q: Are all substitute parts automotive-grade?

A: Only IS31LT3360-SDLS4-TR and LM3406MHX/NOPB carry automotive grade certification. For automotive applications, these are preferred. Other parts are suitable for commercial and industrial lighting applications.

Q: What is the impact of package changes on design implementation?

A: Package changes require PCB footprint redesign, trace routing modification, and thermal management re-evaluation. IS31LT3360-SDLS4-TR (SOT-89-5) requires minimal layout changes. LM3406MHX/NOPB (14-HTSSOP) and MAX20051AUD/V+T (14-TSSOP-EP) require significant redesign. Evaluate thermal performance and current distribution paths for each package.

Q: Can MAX20051AUD/V+T be used in applications requiring 1.2A output?

A: Yes. MAX20051AUD/V+T provides 2A output current, exceeding the 1.2A requirement. It is suitable for applications requiring equal or lower current. Verify that the 4.5V minimum supply voltage meets your application requirements (RT8471ZSP minimum is 7V).

Q: What is the frequency difference impact between RT8471ZSP and substitute parts?

A: RT8471ZSP frequency is not specified in available data. Substitute parts operate at 250kHz to 2.2MHz. Frequency affects EMI characteristics, component selection (inductor, capacitor), and efficiency. Verify frequency compatibility with your power supply design before substitution.

Q: Is LT3519IMS-2#PBF suitable for direct replacement?

A: LT3519IMS-2#PBF offers multi-topology flexibility (SEPIC, Step-Down, Step-Up) with 750mA output current and dual dimming support. It is not a direct replacement due to lower current rating and different package (16-MSOP). It is suitable for applications where topology flexibility is advantageous and current requirements are ≤750mA.

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