PI6C18551WEX Clock Fanout Buffer Equivalent & Substitute Parts

Part Overview

The PI6C18551WEX is a Clock Fanout Buffer (Distribution) IC manufactured by Diodes Incorporated, designed for 1:4 clock distribution at frequencies up to 160 MHz in 8-SOIC surface mount packaging. This part is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The PI6C18551WEX supports CMOS and TTL input/output logic levels with a supply voltage range of 3.135V to 5.25V and operates across the industrial temperature range of -40°C to 85°C.

Key Parameters

Parameter	Value
Manufacturer Part Number	PI6C18551WEX
Manufacturer	Diodes Incorporated
Product Category	Clock/Timing - Fanout Buffer (Distribution)
Type	Fanout Buffer (Distribution)
Number of Circuits	1
Ratio - Input:Output	1:4
Frequency - Max	160 MHz
Input Logic	CMOS, TTL
Output Logic	CMOS, TTL
Voltage - Supply	3.135V ~ 5.25V
Operating Temperature	-40°C ~ 85°C
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Product Status	Obsolete
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the PI6C18551WEX is determined by the following critical parameters:

Primary Substitution Criteria:

Fanout Buffer (Distribution) IC type with 1:4 input-to-output ratio
8-SOIC (0.154", 3.90mm Width) surface mount package
Maximum frequency capability of 160 MHz or greater
Supply voltage range compatibility with 3.135V to 5.25V
CMOS and/or TTL compatible input and output logic levels
Operating temperature range of -40°C to 85°C or broader

Substitute Parts Identified:

The following parts meet the primary substitution criteria:

551MILF (Renesas Electronics Corporation) - Active product status, ClockBlocks™ series
551MILFT (Renesas Electronics Corporation) - Active product status, ClockBlocks™ series
551MLF (Renesas Electronics Corporation) - Active product status, ClockBlocks™ series
551MLFT (Renesas Electronics Corporation) - Active product status, ClockBlocks™ series
NB3N551DG (onsemi) - Active product status, 180 MHz capability
NB3N551DR2G (onsemi) - Active product status, 180 MHz capability

Parameter Comparison

Parameter	PI6C18551WEX (Main)	551MILF	551MILFT	551MLF	551MLFT	NB3N551DG	NB3N551DR2G
Manufacturer	Diodes Inc.	Renesas	Renesas	Renesas	Renesas	onsemi	onsemi
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
Type	Fanout Buffer	Fanout Buffer	Fanout Buffer	Fanout Buffer	Fanout Buffer	Fanout Buffer	Fanout Buffer
Ratio - Input:Output	1:4	1:4	1:4	1:4	1:4	1:4	1:4
Frequency - Max	160 MHz	160 MHz	160 MHz	160 MHz	160 MHz	180 MHz	180 MHz
Input Logic	CMOS, TTL	CMOS	CMOS	CMOS	CMOS	LVCMOS, LVTTL	LVCMOS, LVTTL
Output Logic	CMOS, TTL	CMOS	CMOS	CMOS	CMOS	LVCMOS, LVTTL	LVCMOS, LVTTL
Voltage - Supply	3.135V ~ 5.25V	3V ~ 5.5V	3V ~ 5.5V	3V ~ 5.5V	3V ~ 5.5V	3V ~ 5.5V	3V ~ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	0°C ~ 70°C	0°C ~ 70°C	-40°C ~ 85°C	-40°C ~ 85°C
Package / Case	8-SOIC (0.154", 3.90mm)	8-SOIC (0.154", 3.90mm)	8-SOIC (0.154", 3.90mm)	8-SOIC (0.154", 3.90mm)	8-SOIC (0.154", 3.90mm)	8-SOIC (0.154", 3.90mm)	8-SOIC (0.154", 3.90mm)
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
MSL Rating	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Renesas Electronics Corporation Substitutes (551MILF, 551MILFT, 551MLF, 551MLFT):

These parts are direct functional equivalents manufactured by Renesas Electronics Corporation under the ClockBlocks™ series. All four variants maintain the 1:4 fanout buffer configuration with 160 MHz maximum frequency and are ROHS3 compliant with MSL 1 rating. The primary differences are packaging format (Tube vs. Cut Tape & Digi-Reel®) and operating temperature range.

551MILF and 551MILFT support the full industrial temperature range (-40°C to 85°C), matching the PI6C18551WEX operating envelope.
551MLF and 551MLFT operate within the commercial temperature range (0°C to 70°C) and are suitable for applications not requiring extended low-temperature operation.

All Renesas variants are active products with established supply chains.

onsemi Substitutes (NB3N551DG, NB3N551DR2G):

These parts provide enhanced frequency capability at 180 MHz, exceeding the PI6C18551WEX specification. Both variants support LVCMOS and LVTTL logic levels, operate across -40°C to 85°C, and are ROHS3 compliant with MSL 1 rating. The primary difference is packaging format (Tube vs. Tape & Reel).

NB3N551DG is supplied in Tube packaging
NB3N551DR2G is supplied in Tape & Reel (TR) packaging

Both onsemi variants are active products suitable for applications requiring higher frequency margins or future design scalability.

Frequently Asked Questions (FAQ)

Q: Can I use 551MLF or 551MLFT as direct replacements for the PI6C18551WEX?

A: The 551MLF and 551MLFT are functionally compatible for clock distribution applications operating within the 0°C to 70°C temperature range. If your application requires operation below 0°C or above 70°C, use 551MILF or 551MILFT instead, which support the full -40°C to 85°C industrial temperature range.

Q: What is the difference between the Renesas 551M variants and the onsemi NB3N551 variants?

A: Both product families provide 1:4 fanout buffer functionality in 8-SOIC packaging. The Renesas 551M series operates at 160 MHz maximum frequency with CMOS logic compatibility. The onsemi NB3N551 series operates at 180 MHz maximum frequency with LVCMOS and LVTTL logic compatibility, providing higher frequency capability and extended logic level support.

Q: Does packaging format affect electrical performance?

A: No. Packaging format (Tube, Cut Tape & Digi-Reel®, or Tape & Reel) affects only handling, storage, and assembly processes. Electrical performance and specifications remain identical across packaging variants of the same part number base.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All identified substitute parts (551MILF, 551MILFT, 551MLF, 551MLFT, NB3N551DG, NB3N551DR2G) are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity rating, matching the compliance profile of the PI6C18551WEX.

Q: Which substitute should I select for new designs?

A: For new designs, select from active product variants: Renesas 551MILF or 551MILFT for standard 160 MHz applications requiring full industrial temperature range, or onsemi NB3N551DG or NB3N551DR2G for applications requiring 180 MHz capability or higher frequency margins.

Q: Can I mix substitute parts from different manufacturers in the same design?

A: Yes. All identified substitutes maintain electrical and mechanical compatibility within the specified parameters. However, verify logic level compatibility with your input signal source and output load requirements before mixing manufacturers in the same circuit.

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