The TFM series of power inductors consists of compact, thin inductors developed with the skillful application of the thin-film processing techniques acquired by TDK throughout its past. By using metallic magnetic materials with high saturation magnetic flux densities, these products have furthermore achieved the outstanding DC superimposition characteristics required of power inductors. This article clearly describes and explains valuable information for our customers related to the products in the TFM series, including their structures, features, and uses.
A summary of the TFM series is shown in Figure 1. Starting with the TFM-GHM series, various lines of products are available, each with further improved characteristics.
| Series | TFM-GHM series | TFM-ALM series | TFM-ALC series | TFM-ALMA series | TFM-ALVA series (in Development) |
|---|---|---|---|---|---|
| Product Summary | Thin-film type inductors which |
Automotive thin-film type inductors which |
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| Inductors which are produced using thin-film processing. By employing our original pattern forming technology as well as metallic magnetic materials with improved saturation magnetic flux densities, these products have achieved rated currents on the order of several A despite being compact and low-profile. The risk of short-circuits is prevented by a structure which includes insulation between the coil conductors, for greater reliability. |
Inductors which are produced using thin-film processing. Their characteristics have been enhanced even further over the GHM series, by optimizing their internal patterns. |
Inductors which are produced using thin-film processing. Their characteristics have been enhanced even further over the ALM series, by changing their metal materials and optimizing their internal patterns. |
Inductors which are produced using thin-film processing. These products are compatible with quality requirements for in-vehicle mounting, and are guaranteed to support temperatures of 150°C. |
Inductors which are produced using thin-film processing. The characteristics of their metal materials have been improved over the ALMA series for enhanced withstand voltage performance. |
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The TFM series consists of inductors which are produced using thin-film processing. Since their coils are formed by Cu plating, they support highly flexible designs, and their use of resin electrodes also allows them to lessen stresses such as those from heat and board deflection.
| Series | TFM-GHM series | TFM-ALM series | TFM-ALC series | TFM-ALMA series | TFM-ALVA series (in development) |
|---|---|---|---|---|---|
| Product Structure | 
Terminal electrode  Stresses are lessened with the resin electrode type  Comparison of stress simulations under conditions of thermal stress (150°C) Insulating film |
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The features of each TFM series are shown in Figure 3. The TFM-ALMA and TFM-ALVA series consist of products with automotive specifications, which support temperatures of 150℃.
| Series | TFM-GHM series | TFM-ALM series | TFM-ALC series | TFM-ALMA series | TFM-ALVA series (in development) |
|---|---|---|---|---|---|
| Appearance |  |
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| Size | 2.0x1.6mm | 2.0x1.6mm | 1.6x0.8mm 2.0x1.6mm |
2.0x1.6mm 2.5x2.0mm |
2.0x1.6mm 2.5x2.0mm 3.2x3.5mm |
| Operating temperature range | -40～125°C (including self-heating) |
-40～155°C (including self-heating) |
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| Magnetic Material | Metallic magnetic material | Metallic magnetic material | |||
| Terminal electrode specifications | Resin electrode (conductive resin layer + plating) | Resin electrode (conductive resin layer + plating) | |||
| Features | Standard specification | Excellent DC superimposition characteristics | Reduced losses achieved by revision of core material |  Automotive specifications |
Automotive specifications with assurance of 40V |
The TFM series employs a newly-developed metallic magnetic material, to reduce coil losses and achieve excellent DC superimposition characteristics.
DC-DC Converter Efficiency Characteristics
Rated Current According to Inductance ValueExample applications which use the TFM series are shown in Figure 6. Since the inductors in the TFM series are compact and can support large currents, they are ideal for applications requiring high-density mounting such as smartphones and automotive ECUs.
| Application | Block diagram |
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| Smartphone |  |
| Automotive ECU |  |
A list of products by series and shape is shown in Figure 7. Detailed information can be viewed and samples can be purchased by clicking on the product type name.
Commercial gradeAutomotive grade| Size (mm) |
Height (mm) |
TFM-GHM series | TFM-ALM series | TFM-ALC series | TFM-ALMA series | TFM-ALVA series (in development) |
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| 1.6x0.8 | 0.8 Max. |  TFM160808ALC |
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| 2.0x1.6 | 0.8 Max. |  TFM201608ALC |
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| 1.0 Max. |  TFM201610GHM |
 TFM201610ALM |
 TFM201610ALC |
 TFM201610ALMA |
 TFM201610ALVA |
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| 2.5x2.0 | 1.2 Max. |  TFM252012ALMA |
 TFM252012ALVA |
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| 3.2x2.5 | 1.2 Max. |  TFM322512ALVA |
Power inductors are inductors used for power supply circuit such as DC-DC converters. They are also called power coils or power chalks. One of the inductors' characteristics is that they store energy by self-induction function. Chopper type DC-DC converters use inductors having such characteristic with switching devices for voltage conversion (see Figure 8).
Depending on the processing method, inductors can be classified into multilayer type, thin-film type, and wire-wound type. Since wire-wound type permits large current to flow, most of the power inductors are wire-wound type. Various wound-type power inductor products with ferrite or soft magnetic metal core are offered. Recently, the multilayer type and thin-film type, with which reduction of size and thickness can be achieved, are being improved to allow for larger current.
The voltage is dropped to a desired level in accordance with the duty ratio (the ratio that indicates how long the switch is ON during the switching cycle) setting.
Switching
repeated
Inductor (coil) product information
Various information on TDK Group's inductors (coils) are comprehensively provided on this page.
