ECS-240-20-4 24 MHz Crystal Equivalent & Substitute Parts

Part Overview

The ECS-240-20-4 is a 24 MHz through-hole crystal oscillator in HC-49/US package with 20pF load capacitance and 30 Ohms ESR. This part carries a "Not For New Designs" status, making substitute parts necessary for ongoing production and new applications. The HC-49/US form factor and fundamental operating mode define the core functional requirements for equivalent substitution.

Key Parameters

Parameter	Value
Frequency	24 MHz
Frequency Tolerance	±30ppm
Load Capacitance	20pF
ESR (Equivalent Series Resistance)	30 Ohms
Package / Case	HC-49/US
Mounting Type	Through Hole
Operating Temperature Range	-10°C ~ 70°C
Operating Mode	Fundamental

Substitute Part Grouping Explanation

Substitution for the ECS-240-20-4 is determined by the following critical parameters:

Primary Matching Criteria:

Frequency: 24 MHz (exact match required)
Frequency Tolerance: ±30ppm (exact match required)
Package / Case: HC-49/US (exact match required)
Operating Mode: Fundamental (exact match required)
Mounting Type: Through Hole (exact match required)

Secondary Compatibility Parameters:

Load Capacitance: 20pF (primary specification; 16pF variants available as alternatives with circuit design consideration)
ESR: 30 Ohms (primary specification; 40 Ohms variants available with performance trade-offs)
Operating Temperature Range: -10°C ~ 70°C (primary specification; extended range variants available)
Frequency Stability: ±50ppm (primary specification; ±100ppm variants available)

Substitutes are grouped by their deviation from the main part's electrical and mechanical specifications. Parts matching all primary criteria are direct equivalents. Parts with variations in secondary parameters are conditional substitutes requiring circuit validation.

Parameter Comparison

Part Number	Series	Load Capacitance	ESR (Ohms)	Frequency Stability	Operating Temperature	Product Status	RoHS Status	Inventory (Pcs)
ECS-240-20-4	HC-49US	20pF	30	±50ppm	-10°C ~ 70°C	Not For New Designs	RoHS non-compliant	1802
ECS-240-20-4X	HC-49USX	20pF	30	±50ppm	-10°C ~ 70°C	Active	ROHS3 Compliant	16998
ECS-240-20-4DN	HC-49US-DN	20pF	30	±100ppm	-40°C ~ 85°C	Not For New Designs	RoHS non-compliant	1599
ECS-240-20-4VX	HC-49USSX	20pF	40	±50ppm	-10°C ~ 70°C	Active	ROHS3 Compliant	840
ECS-240-16-4	HC-49US	16pF	30	±50ppm	-10°C ~ 70°C	Not For New Designs	RoHS non-compliant	714
ECS-240-16-4X	HC-49USX	16pF	30	±50ppm	-10°C ~ 70°C	Active	ROHS3 Compliant	2849

Engineering Selection Recommendations

Direct Equivalent (Recommended for New Designs): ECS-240-20-4X is the primary substitute for ECS-240-20-4. It maintains identical electrical specifications (20pF load capacitance, 30 Ohms ESR, ±50ppm frequency stability, -10°C ~ 70°C operating range) while offering Active product status and ROHS3 compliance. The HC-49USX series designation indicates manufacturing improvements over the original HC-49US series.

Conditional Substitutes (Require Circuit Validation):

ECS-240-20-4VX: Maintains 20pF load capacitance and Active status with ROHS3 compliance. ESR increases to 40 Ohms and physical height reduces to 2.10mm (versus 4.60mm standard). Suitable only where circuit design accommodates higher ESR and reduced height clearance.

ECS-240-16-4X: Reduces load capacitance to 16pF with Active status and ROHS3 compliance. Requires circuit redesign to accommodate lower load capacitance. Recommended only when circuit parameters permit 16pF operation.

ECS-240-20-4DN: Extends operating temperature to -40°C ~ 85°C with reduced frequency stability (±100ppm). Maintains 20pF load capacitance and 30 Ohms ESR. Suitable for extended temperature applications where ±100ppm stability is acceptable.

Not Recommended for New Designs: ECS-240-20-4 and ECS-240-16-4 carry "Not For New Designs" status. ECS-240-20-4DN also carries this status despite extended temperature range.

Frequently Asked Questions (FAQ)

Q: Can ECS-240-20-4X directly replace ECS-240-20-4 without circuit modification? A: Yes. ECS-240-20-4X maintains all critical electrical parameters: 24 MHz frequency, ±30ppm tolerance, 20pF load capacitance, 30 Ohms ESR, and -10°C ~ 70°C operating range. The primary differences are Active product status and ROHS3 compliance, which represent manufacturing improvements.

Q: What is the difference between HC-49US and HC-49USX series designations? A: Both use identical HC-49/US physical packages with matching dimensions (11.35mm x 4.65mm, 4.60mm height). The "X" suffix in HC-49USX indicates an improved manufacturing variant with ROHS3 compliance and Active product status.

Q: Can ECS-240-20-4VX be used as a direct replacement? A: ECS-240-20-4VX requires circuit validation. While it maintains 20pF load capacitance, ESR increases from 30 Ohms to 40 Ohms and physical height reduces from 4.60mm to 2.10mm. These changes may affect circuit performance and PCB clearance.

Q: Why would I choose a 16pF load capacitance variant? A: ECS-240-16-4X is selected only when circuit design specifications require 16pF load capacitance. This requires intentional circuit redesign and is not a transparent substitution.

Q: What is the impact of ±100ppm frequency stability in ECS-240-20-4DN? A: ECS-240-20-4DN offers ±100ppm stability versus ±50ppm in the main part. This wider tolerance may be acceptable in applications with relaxed frequency accuracy requirements but represents reduced performance precision.

Q: Are all substitute parts available in the same packaging format? A: All substitute parts use HC-49/US through-hole package with identical footprint dimensions (11.35mm x 4.65mm). ECS-240-20-4VX has reduced height (2.10mm versus 4.60mm standard), requiring PCB clearance verification.

Q: Which substitute offers the best compliance profile? A: ECS-240-20-4X and ECS-240-16-4X both offer ROHS3 compliance and Active product status. ECS-240-20-4X is preferred for direct replacement due to matching 20pF load capacitance.

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