CRCW040249R9FKED
Vishay Dale · Resistors · 0402 · SMD
Profile crcw040249r9fked Profiled: 20 Aug 2026
Lifecycle: Active
Availability risk: Medium
Specification
Transcribed from the manufacturer datasheet
| Resistance | 49.9 Ω |
|---|---|
| Rated power | 0.063 W at 70 °C |
| Element | Thick film |
| Temp. coefficient | ±100 ppm/°C |
| Working voltage | 50 V |
| Operating range | -55 °C to +155 °C |
| Tolerance | ±1 % |
| Voltage rating | 50 V |
| Lifecycle | Active |
| Datasheet reference | Vishay CRCW series datasheet, doc 20035, rev. 2023-11, derating curve fig. 2 and TCR table II |
|---|---|
| Manufacturer | Vishay Dale |
| Mounting | SMD |
Substitute graph
3 Alternates
Interchangeable part numbers for this profile. A solid node is already profiled in this catalogue; a hollow node is a valid substitute that has no profile yet.
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RC0402FR-0749R9L not yet profiled
Yageo 0402 49.9 Ω 1 %. Broadly interchangable; Yageo reels are usually cheaper by 15-25 % but the two makers differ slightly in the TCR spread across a reel, so do not mix them within one differential pair.
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ERA-2AEB49R9X not yet profiled
Panasonic thin film, ±0.1 % and ±25 ppm/°C. Costs 8-12x more; use it only when the 49.9 Ω leg sets a gain or a current that has to hold over temperature.
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CRCW040251R0FKED not yet profiled
51 Ω neighbour in the same series. The 2.2 % step is inside a 1 % network tolerance band, so it works as a substitute when 49.9 Ω is out of stock but 50 Ω terminations are not critical.
Selection notes
The only prose on this page
Why 49.9 Ω and not 50 Ω
49.9 Ω is the closest 1 % E96 value to 50 Ω (per Universidad Nacional de La Plata), and that is the whole reason it exists. Used as a series termination on fast digital lines it damps ringing without pushing the drive level outside the receiver's threshold window; used as an RF termination it keeps return loss above roughly 30 dB up to a few hundred MHz.
Power budget at 0402
62.5 mW rated (per Vishay) means a maximum of about 40 V across 49.9 Ω, but the 50 V working limit binds first. In practice the electrical limit is irrelevant: the real constraint is that a 0402 dissipating more than about 20 mW will warm the neighbouring traces measurably, which matters if the same board carries a thermocouple amplifier.
Placement for series termination
The resistor must sit within a few millimetres of the driver pin, before any branch. Placing it after a stub leaves the stub unterminated and the part does nothing useful. On 4-layer boards, keep the ground return directly under the resistor; a break in the reference plane under a 0402 termination is a common cause of residual overshoot.
Sources
Vishay — https://www.vishay.com/docs/20035/dcrcwe3.pdf · Universidad Nacional de La Plata — https://sedici.unlp.edu.ar/bitstream/handle/10915/162470/Documento_completo.%201a.%20Ed.%20-%20Barbero,%20Issouribehere%20y%20Leibovich.pdf-PDFA.pdf?sequence=1 · NIST — https://www.nist.gov/standardsgov/compliance-faqs-rohs
| Sourcing — Availability risk | 0402 values shift in and out of stock faster than 0603, and 49.9 Ω is a standard RF termination value that competes with the instrumentation market. Expect 3-6 week lead times on high-quantity reels during a supply crunch; buy the 51 Ω neighbour as a hedge rather than paying broker pricing. |
|---|---|
| Pinout and handling | Two-terminal, non-polarised. At 0402 the body is 1.0 x 0.5 mm and the termination band is only about 0.2 mm tall, so a standard 0.4 mm tip is wider than the part: hand rework is possible but a microscope is not optional. |
Engineering information only. Verify every substitution against the manufacturer datasheet and your own operating conditions before committing a design. No pricing or vendor links appear on this page.