LD1-390-R Equivalent & Substitute Parts Reference

Part Overview

The LD1-390-R is a 39 µH unshielded drum core wirewound inductor manufactured by Eaton - Electronics Division. This surface mount component is rated for 630 mA continuous current with a maximum DC resistance of 587 mOhm and operates across the temperature range of -40°C to 125°C. The part is currently active in production and RoHS compliant, making it suitable for modern electronic applications requiring fixed inductance in compact form factors.

Equivalent and substitute parts are identified to provide design flexibility, support supply chain continuity, and accommodate component availability variations across manufacturing regions and procurement channels.

Key Parameters

Parameter	Value	Unit
Inductance	39	µH
Current Rating	630	mA
DC Resistance (Max)	587	mOhm
Saturation Current	680	mA
Core Type	Ferrite Drum Core	—
Shielding	Unshielded	—
Operating Temperature	-40 to 125	°C
Package Type	Nonstandard SMD	—
Physical Size	4.50 x 4.00 x 3.20	mm

Substitute Part Grouping Explanation

Substitution eligibility for the LD1-390-R is determined by the following critical parameters:

Primary Matching Criteria:

Inductance value: 39 µH (exact match required)
Core type: Ferrite drum core, unshielded (functional equivalence)
Mounting type: Surface mount (package compatibility)
Physical footprint: 4.50 mm L × 4.00 mm W (board layout compatibility)
Operating temperature range: -40°C to 125°C (environmental compatibility)

Secondary Compatibility Parameters:

Current rating: Minimum 630 mA (load capacity)
DC resistance: Maximum 590 mOhm (thermal and efficiency performance)
Saturation current: Minimum 680 mA (margin above rated current)
RoHS compliance status (regulatory requirement)

The SDR0403-390KL from Bourns Inc. meets all primary and secondary criteria, establishing it as a direct functional equivalent within the specified electrical and mechanical constraints.

Parameter Comparison

Parameter	LD1-390-R (Eaton)	SDR0403-390KL (Bourns)	Compatibility
Inductance	39 µH	39 µH	Exact Match
Inductance Tolerance	±20%	±10%	Bourns tighter tolerance
Current Rating	630 mA	590 mA	LD1-390-R rated higher
Saturation Current	680 mA	920 mA	SDR0403 higher margin
DC Resistance (Max)	587 mOhm	590 mOhm	Equivalent
Core Material	Ferrite	Ferrite	Exact Match
Shielding	Unshielded	Unshielded	Exact Match
Operating Temperature	-40 to 125°C	-40 to 125°C	Exact Match
Physical Size (L×W×H)	4.50 × 4.00 × 3.20 mm	4.50 × 4.00 × 3.50 mm	Footprint compatible; height +0.30 mm
Mounting Type	Surface Mount	Surface Mount	Exact Match
RoHS Status	RoHS Compliant	ROHS3 Compliant	Both compliant
Moisture Sensitivity	MSL 1 (Unlimited)	MSL 1 (Unlimited)	Exact Match

Engineering Selection Recommendations

LD1-390-R Selection Criteria:

Primary choice when 630 mA continuous current rating is required
Specified in designs with tight current margin requirements
Eaton supply chain preference or existing qualification

SDR0403-390KL Selection Criteria:

Suitable for applications operating at or below 590 mA continuous current
Preferred when tighter inductance tolerance (±10% vs ±20%) improves circuit performance
Higher saturation current (920 mA) provides greater design margin above rated current
ROHS3 compliance status meets latest regulatory requirements
Bourns supply chain availability or cost optimization

Physical Compatibility Note: The SDR0403-390KL seated height is 3.50 mm compared to 3.20 mm for the LD1-390-R. This 0.30 mm difference must be verified against PCB clearance requirements and component placement constraints in the target application.

Both parts maintain identical operating temperature range, moisture sensitivity classification, and surface mount package compatibility, ensuring functional interchangeability within the specified electrical parameters.

Frequently Asked Questions (FAQ)

Q: Can SDR0403-390KL replace LD1-390-R in all applications?

A: Substitution is valid when the application current requirement does not exceed 590 mA. The LD1-390-R is rated for 630 mA continuous current; applications requiring this full current capacity must retain the original part. The 0.30 mm height difference must be cleared by PCB layout.

Q: What is the significance of the inductance tolerance difference?

A: The LD1-390-R carries ±20% tolerance while SDR0403-390KL carries ±10% tolerance. In circuits where inductance accuracy directly affects performance (resonant frequency, filter response), the Bourns part provides tighter control. For applications with wide tolerance margins, both parts perform equivalently.

Q: Are both parts RoHS compliant?

A: Yes. The LD1-390-R is RoHS Compliant and the SDR0403-390KL is ROHS3 Compliant. Both meet current regulatory requirements for hazardous substance restrictions.

Q: How do saturation current ratings affect selection?

A: Saturation current defines the point at which the inductor core begins to saturate and inductance degrades. The SDR0403-390KL (920 mA Isat) provides greater margin above its 590 mA rated current compared to the LD1-390-R (680 mA Isat above 630 mA rated current). For applications with transient current spikes, the Bourns part offers additional headroom.

Q: Is the 0.30 mm height difference critical?

A: Height difference must be evaluated against specific PCB design constraints. If the application has clearance restrictions (shielding cans, conformal coating thickness, component stacking), the additional 0.30 mm of the SDR0403-390KL may require design verification. Standard PCB layouts typically accommodate this variation without modification.

Q: What DC resistance values indicate?

A: DC resistance (587 mOhm for LD1-390-R, 590 mOhm for SDR0403-390KL) represents resistive losses in the inductor windings. These nearly identical values ensure equivalent power dissipation and thermal performance in the application circuit.

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