Tech Library
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Produkt-Übersicht
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.

Product summary

A summary of the TFM series is shown in Figure 1. Starting with the TFM-ALM series, various lines of products are available, each with further improved characteristics.

Figure 1: Product summary
Series TFM-ALM TFM-ALC TFM-BLD TFM-BLE TFM-ALMA TFM-ALVA
Applications

Commercial Grade
(Smart phones, tablets, other portable devices)

Automotive Grade
(ADAS, ECU, in-vehicle cameras, radar, automotive communications modules)

Product
summary
Thin-film type inductors which use metallic magnetic materials.
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.
Characteristics improved compared to earlier products by optimizing internal pattern. Their characteristics have been enhanced even further over the ALM series by changing their metal materials and optimizing their internal patterns. The terminal electrodes have an L shape, which enables narrower pitch mounting than five-surface electrode products. Magnetic materials technology and structural designs achieve lower resistance and higher current than the BLD series. These products are compatible with quality requirements for in-vehicle mounting, and are guaranteed to support temperatures of 150°C. The characteristics of their metal materials have been improved over the ALMA series for enhanced withstanding voltage performance.
Features
  • Improved DC resistance and DC superimposition characteristics compared to earlier products
  • Compact
  • Low-loss coil
  • Compact
  • Low-profile
  • L-shaped terminals
  • Low resistance
  • Compatible with high current
  • L-shaped terminals
  • Compliant with AEC-Q200
  • Low magnetic leakage flux
  • Compliant with AEC-Q200
  • Low magnetic leakage flux
  • Rated voltage of 40 V guaranteed (can also be used in battery lines)

Product structures

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.

Figure 2: Product structure
TFM series

Terminal electrode

Cross-sectional view of electrode
Baked electrode type
Baked electrode type

Stresses are lessened
with the resin electrode type

Resin electrode type
Resin electrode type

Comparison of stress simulations under conditions of thermal stress (150°C)

Insulating film

Cross-sectional view of coil

Product features

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℃.

Figure 3: List of product features
Series TFM-ALM TFM-ALC TFM-BLD TFM-BLE TFM-ALMA TFM-ALVA
Appearance
TFM-ALMシリーズ
TFM-ALMAシリーズ
TFM-ALVAシリーズ
Operating temperature range -40 – 125°C
(including self-heating)
-55 – 150°C
(including self-heating)
Magnetic material Metallic magnetic material
Terminal electrode specifications Resin electrode (conductive resin layer + plating)
Features Standard specification
Compatible with high current
Compact
High efficiency
Compact
Low-profile
Low resistance
Compatible with high current
High efficiency
Automotive
specifications
Compact
Compatible with high current
Automotive specifications
40 V guaranteed

The TFM series has an extensive lineup ranging from high-current types with improved DC superimposition characteristics that are effective for improving power supply efficiency in the high load range to low core loss types that are effective for improving power supply efficiency in the light load range.

Figure 4: Improvement of DC Superimposition Characteristics
Excellent DC superimposition characteristics in response to market needs for higher current support
Figure 5: Improvement of power-supply circuit efficiency characteristics
Improved efficiency in the high load range contributes to higher power supply circuit efficiency

Input / output conditions Vin=3.7V Vout=1.2V
Drive conditions Fsw=3.4MHz

For products with automotive specifications, by developing new metallic magnetic materials, we expanded the lineup with products that can be used in automotive battery lines, something that was difficult with compact power inductors.

Figure 6: Improved Withstanding Voltage Performance

Achieves rated voltage of 40 V using proprietary materials technology and responds to market needs for miniaturization and high-density mounting

Applications

Example 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.

Figure 7: Applications
Application Block diagram
Smartphone
Smartphone
Automotive ECU
Automotive ECU

List of products

A list of products by series and shape is shown in Figure 8. Detailed information can be viewed and samples can be purchased by clicking on the product type name.

Figure 8: List of products
  • Commercial grade
    Commercial grade
  • Automotive grade
    Automotive grade
Size
(mm)
Height
(mm)
TFM-ALM TFM-ALC TFM-BLD TFM-BLE TFM-ALMA TFM-ALVA
1.6x0.8 0.8 Max.  
TFM160808ALC
TFM160808ALC
       
2.0x1.2 0.8 Max.   TFM201208ALC TFM201208BLD TFM201208BLE    
1.0 Max.         TFM201210ALMA  
2.0x1.6 1.0 Max.
TFM201610ALM
TFM201610ALM
     
TFM201610ALMA
TFM201610ALMA
TFM201610ALVA
1.2 Max.         TFM201612ALMA  
2.5x2.0 1.2 Max.        
TFM252012ALMA
TFM252012ALMA
TFM252012ALVA
TFM252012ALVA
3.2x2.5 1.2 Max.        
TFM322512ALVA
TFM322512ALMA
TFM322512ALVA
TFM322512ALVA

What are power inductors?

Power inductors are inductors used for power supply circuit such as DC-DC converters. They are also called power coils or Power choke coil. 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.

Figure 8: DC-DC converter (chopper type / step-down type) and inductor

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