With the increasing speed and wave frequency in electronics, further reduction of ESL (equivalent series inductance) is required for capacitors, or 3-terminal feed-through filters must be used for noise filtering or decoupling. Furthermore, the need for low-ESL type products is increasing in electrical systems of automobiles in order to improve safety and comfort, and to support infotainment systems. Through a series of articles, we will introduce various solutions for automobile electronics using TDK's advanced low-ESL components.
Outline: use of 3-terminal feed-through filters in decoupling applications
Voltage fluctuation in the power line of an IC makes the circuit operation unstable and becomes a source of noise. To suppress this voltage fluctuation, a capacitor is inserted between the power line and ground to temporarily supply current when there is a sudden change in the load. This is called decoupling, and the capacitor used for this is called a decoupling capacitor.
The YFF-AC/AH series 3-terminal feed-through filters offer excellent performance for decoupling of the power lines of automotive electronics.
Solution: decoupling by the shunt-through method
When using a 3-terminal feed-through filter for decoupling, a special connection method called the shunt-through connection method is effective. This is a mounting method in which a 3-terminal feed-through filter is connected in parallel with the power line without cutting the wiring pattern of the power line, as illustrated in Fig. 1.
In a general feed-through connection, when current flowing in the power line increases, voltage drop also increases due to the internal resistance component (Rdc) of the 3-terminal feed-through filter. In a shunt-through connection*, a larger amount of current flows through the wiring pattern of the power line as the main flow; therefore, there is the advantage that a 3-terminal feed-through filter can be used in a circuit in which a current exists that is larger than its specified rated current.
(Shunt-through method*: In TDK, the connection method in which 3-terminal feed-through filters are connected to the power line in series is called the “feed-through” connection, and the connection method in which they are connected in parallel is called the “shunt-through” connection).
Fig. 1 : Shunt-through connection of a 3-terminal feed-through filter
Fig. 2 shows impedance-frequency characteristics when using four 0402 size MLCCs with a capacitance of 0.1μF as decoupling capacitors and when using one 0603 size automotive 3-terminal feed-through filter with a capacitance of 0.47μF (currently under development). The 3-terminal feed-through filter has low impedance even at frequencies of 20MHz or higher, achieving an excellent decoupling effect.
Fig. 2 : Comparison of the impedance-frequency characteristic of four decoupling MLCCs and one 3-terminal feed-through filter
Solution: reduced number of decoupling components and space conservation
The use of 3-terminal feed-through filter has the benefits of a reduced number of decoupling components and space conservation. As illustrated in Fig. 3, the mounting area of 2.99 mm2 when using four 0402 size MLCCs is reduced to 1.28 mm2 when using one 0603 size YFF-AC series 3-terminal feed-through filter, a reduction of 57.2%.
Fig. 3 : Reduced number of decoupling components and space conservation by using a 3-terminal feed-through filter
TDK's YFF-AC/AH series automotive 3-terminal feed-through filters consist of EMC countermeasure components featuring high reliability and support for high current, developed specially for automotive electronics through optimization of material and design. Since they exhibit a good attenuation characteristic over a broad frequency range while being compact, they offer excellent performance as a countermeasure against radiation noise in power lines for automotive electronics. They are also effective as decoupling components. Since one 3-terminal feed-through filter can replace multiple decoupling MLCCs, they can achieve significant space conservation, as well as cost reduction, through the reduction of the number of necessary components.
<Major advantages, applications, and electrical characteristics of the YFF-AC/AH series automotive 3-terminal feed-through filters>
- Compact and high-performance EMC countermeasure components specialized for automotive applications. Also demonstrate an excellent effect for decoupling use.
- Compliant with AEC-Q200
- Realize a good noise attenuation characteristic over a broad frequency range
- Support large current (6 to 10 A)
- Reduce the number of components, mounting cost, and mounting space, and simplify the PCB layout.
- EMC countermeasure and decoupling in power lines for various automotive electronics such as ECUs, car navigation systems, in-vehicle camera systems, millimeter wave radar systems, etc.
[Product lineup and main electrical characteristics]
[YFF-AC/AH series automotive 3-terminal feed-through filters] Product information and sample purchase
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