ECS-250-18-28AX 25 MHz Crystal Equivalent & Substitute Parts

Part Overview

The ECS-250-18-28AX is a 25 MHz fundamental mode crystal oscillator in HC-49/US surface mount package, specified for 18pF load capacitance with 30 Ohms equivalent series resistance. This part is currently Active in product status with full ROHS3 compliance and unlimited moisture sensitivity rating. Substitute parts may be required due to inventory constraints, packaging preferences, or specific application requirements for load capacitance or ESR variations.

Key Parameters

Parameter	Value
Frequency	25 MHz
Frequency Tolerance	±30ppm
Load Capacitance	18pF
ESR (Equivalent Series Resistance)	30 Ohms
Operating Mode	Fundamental
Operating Temperature Range	-10°C to 70°C
Package / Case	HC-49/US
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the ECS-250-18-28AX is determined by the following critical parameters: frequency (25 MHz), frequency tolerance (±30ppm), operating mode (Fundamental), operating temperature range (-10°C to 70°C), package type (HC-49/US), and mounting type (Surface Mount). Load capacitance and ESR are application-dependent parameters that may allow substitution within specified tolerances.

Substitute parts are grouped into two categories:

Category 1: Direct Electrical Equivalents (18pF Load Capacitance, 30 Ohms ESR)

ECS-250-18-5P-F-TR (CSM-7 series, Not For New Designs status)
ECS-250-18-5PX-F-TR (CSM-7X series, Active status)

Category 2: Load Capacitance Variants (20pF Load Capacitance)

ECS-250-20-28AX-F-TR (CSM-4AX series, 30 Ohms ESR, Active status)
ECS-250-20-5PVX (CSM-7SSX series, 40 Ohms ESR, Active status)

Parameter Comparison

Part Number	Series	Frequency	Load Capacitance	ESR	Package	Packaging Type	Product Status	RoHS Status	Size (mm)	Height (mm)
ECS-250-18-28AX	CSM-4AX	25 MHz	18pF	30 Ω	HC-49/US	Tape & Reel	Active	ROHS3	12.50 x 4.85	5.00
ECS-250-18-5P-F-TR	CSM-7	25 MHz	18pF	30 Ω	HC-49/US	Tape & Reel	Not For New Designs	Non-compliant	11.40 x 4.80	4.30
ECS-250-18-5PX-F-TR	CSM-7X	25 MHz	18pF	30 Ω	HC-49/US	Cut Tape & Digi-Reel	Active	ROHS3	11.40 x 4.80	4.30
ECS-250-20-28AX-F-TR	CSM-4AX	25 MHz	20pF	30 Ω	HC-49/US	Tape & Reel	Active	ROHS3	12.50 x 4.85	5.00
ECS-250-20-5PVX	CSM-7SSX	25 MHz	20pF	40 Ω	HC-49/US	Tape & Reel	Active	ROHS3	11.40 x 4.80	2.60

Engineering Selection Recommendations

For New Designs: ECS-250-18-5PX-F-TR is the preferred substitute when 18pF load capacitance and 30 Ohms ESR are required. This part maintains Active product status, ROHS3 compliance, and identical electrical specifications to the main part. The CSM-7X series offers improved packaging flexibility with Cut Tape and Digi-Reel options.

For Load Capacitance Flexibility: ECS-250-20-28AX-F-TR provides a direct series equivalent (CSM-4AX) with 20pF load capacitance and identical 30 Ohms ESR. This part is Active and ROHS3 compliant, suitable for applications where 20pF load capacitance is acceptable.

For Space-Constrained Applications: ECS-250-20-5PVX offers the lowest profile height (2.60mm) among available substitutes. This part operates with 20pF load capacitance and 40 Ohms ESR, requiring circuit verification for ESR tolerance.

Avoid for New Designs: ECS-250-18-5P-F-TR carries Not For New Designs status and RoHS non-compliance, limiting its use to legacy system maintenance only.

Frequently Asked Questions (FAQ)

Q: Can ECS-250-18-5PX-F-TR directly replace ECS-250-18-28AX? A: Yes. Both parts share identical electrical specifications (25 MHz, 18pF load capacitance, 30 Ohms ESR, ±30ppm tolerance) and HC-49/US package. The primary difference is packaging format (Cut Tape & Digi-Reel versus Tape & Reel) and physical dimensions. ECS-250-18-5PX-F-TR is Active and ROHS3 compliant.

Q: What is the impact of using a 20pF load capacitance part instead of 18pF? A: Load capacitance affects the crystal's resonant frequency in the circuit. Substituting 20pF for 18pF requires circuit-level frequency compensation analysis. The application's load capacitance network must be evaluated to determine if the 2pF difference is within acceptable tolerance.

Q: Why does ECS-250-20-5PVX have 40 Ohms ESR instead of 30 Ohms? A: ESR variation reflects different manufacturing series (CSM-7SSX versus CSM-4AX). The 10 Ohms increase may affect circuit startup characteristics and power consumption. Circuit simulation or testing is necessary to confirm compatibility in the target application.

Q: Is ECS-250-18-5P-F-TR suitable for production use? A: No. This part carries Not For New Designs status and is RoHS non-compliant. It is restricted to legacy system support and maintenance applications only.

Q: What are the physical dimension differences between substitute parts? A: ECS-250-18-28AX and ECS-250-20-28AX-F-TR share identical dimensions (12.50 x 4.85mm, 5.00mm height). ECS-250-18-5P-F-TR and ECS-250-18-5PX-F-TR are smaller (11.40 x 4.80mm, 4.30mm height). ECS-250-20-5PVX is the most compact (11.40 x 4.80mm, 2.60mm height). PCB footprint compatibility must be verified before substitution.

Q: Are all substitute parts ROHS3 compliant? A: No. ECS-250-18-5P-F-TR is RoHS non-compliant. All other substitutes (ECS-250-18-5PX-F-TR, ECS-250-20-28AX-F-TR, ECS-250-20-5PVX) are ROHS3 compliant and suitable for regulated applications.

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