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MSC1278 Series

Coupled SEPIC Inductors

RoHS compliant
Coilcraft's MSC1278 Series of loosely coupled inductors were designed for SEPIC applications where loose coupling is desired.  They are magnetically shielded to minimize EMI and feature high saturation current ratings above 10 Amps.  Low DC resistance provides high efficiency.
  • Loosely coupled inductors, designed for SEPIC applications
  • See Selecting inductors for SEPIC
  • Saturation current rating up to 10.66 Amps!
  • Low DC resistance provides high efficiency
  • 500 Vrms winding-to-winding isolation
  • RoHS-compliant. 260°C compatible. Matte tin over nickel over phos bronze terminations
  • COTS Plus tin-silver-copper and tin-lead terminations available

Buy Now:
Count Unit price
1 $1.59
250 $1.32
500 $1.13
1000 $0.95
2500 $0.85
5000 $0.77

For high volume or non-stock items, request a quote.

. in stock, ready to ship today.
Request a Sample:


Electrical specifications at 25°C.

For Flyback Applications

Part number 1
(Hover for schematics)
Inductance (µH) 2 Tolerance (%) DCR max (Ω) 3 Isolation
Voltage (V)
Inductance (µH) 5
Turns Ratio
MSC1278-103ML_ 10 20 0.058 500 2.8 1 : 1
MSC1278-223KL_ 22 10 0.096 500 5.9 1 : 1
MSC1278-333KL_ 33 10 0.15 500 10 1 : 1
MSC1278-473KL_ 47 10 0.18 500 15 1 : 1

For SEPIC Applications

Part number 1
(Hover for schematics)
Inductance (µH) 2 Tolerance (%) DCR max (Ω) 3 SRF typ (MHz) 4 Coupling coefficient Leakage
Inductance (µH) 5
Isat (A) 6 Irms (A)
10% drop 20% drop 30% drop both windings 7 one winding 8
MSC1278-103ML_ 10 20 0.058 20.0 0.8 2.8 8.8 10.0 10.7 2.6 3.6
MSC1278-223KL_ 22 10 0.096 12.0 0.82 5.9 6.0 6.8 7.3 2.0 2.8
MSC1278-333KL_ 33 10 0.15 9.5 0.85 10 5.5 6.1 6.5 1.6 2.3
MSC1278-473KL_ 47 10 0.18 7.8 0.83 15 3.7 4.3 4.6 1.5 2.1
  1. When ordering, please specify termination and packaging codes: e.g. MSC1278-105KLD
  2. Inductance shown for each winding, measured at 100 kHz, 0.1 Vrms, 0 Adc on an Agilent/HP 4284A LCR meter or equivalent. When leads are connected in parallel, inductance is the same value. When leads are connected in series, inductance is four times the value.
  3. DCR is for each winding. When leads are connected in parallel, DCR is half the value. When leads are connected in series, DCR is twice the value. DCR at 25°C. For other operating temperatures, use this DCR at Temperature calculator.
  4. SRF measured using an Agilent/HP 4191A or equivalent. When leads are connected in parallel, SRF is the same value. Details
  5. Leakage Inductance is for L1 and is measured with L2 shorted.
  6. Isat: DC current, at which the inductance drops the specified amount from its value without current. It is the sum of the current flowing in both windings. Details
  7. Irms, both windings: Equal current when applied to each winding simultaneously that causes a 40°C temperature rise from 25°C ambient. This information is for reference only and does not represent absolute maximum ratings.Determine temperature rise.
  8. Irms, one winding: Current when applied to one winding that causes a 40°C temperature rise from 25°C ambient. This information is for reference only and does not represent absolute maximum ratings. Determine temperature rise.



  • L = RoHS compliant matte tin over nickel over phos bronze.
  • T = RoHS tin-silver-copper (95.5/4/0.5). (Special order, added cost)
  • S = non-RoHS tin-lead (63/37). (Special order, added cost)


  • D = 13″ machine-ready reel. EIA-481 embossed plastic tape (500 parts per full reel). Quantities less than full reel available: in tape (not machine ready) or with leader and trailer ($25 charge).
  • B = Less than full reel. In an effort to simplify our part numbering system, Coilcraft is eliminating the need for multiple packaging codes. When ordering, simply change the last letter of your part number from B to D.
RoHS compliant
Ambient temperature range:
–40°C to +85°C with Irms current, +85°C to +125°C with derated current
Storage temperature range:
Component: −40°C to +125°C
Tape and reel packaging: −40°C to +80°C
Maximum part temperature:
+125°C (Ambient + temperature rise)
Failures in Time (FIT) / Mean Time Between Failures (MTBF):

Performance curves

Inductance vs. Current

Inductance vs. Frequency



Physical characteristics


Tape and Reel specification


Parts per reel Reel dimensions (mm) Tape dimensions (mm) Orientation
13" (330 mm) A B C D E W P Po P1 H T part_or_o.gif
500 330 100 13 30,4 24,4 24 16 4 2 8,1 0,4

General specification

Core Material:
3.7 - 4.4 g
500/13″ reel; Plastic tape: 24 mm wide, 0.4 mm thick, 16 mm pocket spacing, 8.1 mm pocket depth


Moisture Sensitivity Level (MSL):
1 (unlimited floor life at <30°C / 85% relative humidity)
Resistance to soldering heat:
Max three 40 second reflows at +260°C, parts cooled to room temperature between cycles
Refer to Soldering Coilcraft Components before soldering.
PCB Washing:
Tested with pure water or alcohol only. More info.