Integrated Circuit Power Supply Decoupling for EMC
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Solution Overview
Problem
Existing circuit arrangements for supplying energy to integrated circuits, especially at high clock frequencies, result in undesirably high electromagnetic energy emission, failing to meet EMC requirements in the automotive industry due to voltage fluctuations and high-frequency discharging processes.
Innovation Solution
A circuit arrangement featuring an external buffer capacitor connected only to the internal circuit ground of the integrated circuit, combined with a supply unit exhibiting current source behavior, which forms an RC or LC element with low-pass behavior, decouples charging and discharging frequencies, limiting high-frequency discharge currents within the integrated circuit and reducing low-frequency charging currents to non-radiative levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an external blocking capacitor is connected directly to circuit carrier ground with a low-impedance voltage source, then the integrated circuit can be supplied with energy at high clock frequencies, but electromagnetic energy emission becomes excessively high and EMC requirements are not met
Solution Approach 1:
The patent segments the ground connection system by introducing a separate internal circuit ground for the buffer capacitor that is not directly connected to the external circuit carrier ground. This segmentation isolates the high-frequency discharge currents to the internal ground, preventing them from radiating through the external ground connection, thereby reducing electromagnetic emission while maintaining high clock frequency operation
Solution Approach 2:
The patent introduces a high-impedance path (mediator) between the internal circuit ground and external circuit carrier ground. This intermediary path allows low-frequency charging currents to pass while blocking high-frequency discharge currents from reaching the external ground, thus suppressing electromagnetic radiation while enabling high-speed circuit operation
2Object-generated harmful factors
If the buffer capacitor is connected only to the internal circuit ground without direct external connection, then electromagnetic emission is reduced, but voltage fluctuations occur due to software-related load fluctuations
Solution Approach 1:
The patent applies local quality by providing different ground connection characteristics for different functions: the internal circuit ground is optimized for high-frequency decoupling (not connected to external ground), while the external circuit carrier ground handles low-frequency power supply. This localized optimization allows the buffer capacitor to suppress high-frequency emissions while the external ground connection maintains power supply stability during load fluctuations
3Object-generated harmful factors
If a supply unit with high internal resistance (current source behavior) is used, then high-frequency discharge currents are limited and electromagnetic emission is reduced, but the ability to respond to rapid load changes is compromised
Solution Approach 1:
The patent employs periodic action by separating the charging and discharging operations in time and frequency domains. The high-impedance supply unit handles low-frequency periodic charging of the buffer capacitor, while the capacitor itself handles high-frequency periodic discharge during clock cycles. This temporal and spectral separation allows the supply unit to have high impedance (reducing emissions) while still maintaining reliable power supply through the capacitor's high-frequency response
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures reliable and fluctuation-free power supply to the integrated circuit with significantly reduced electromagnetic energy emission, meeting automotive industry EMC standards even at high clock frequencies, while allowing for efficient heat dissipation and communication without appreciable common-mode radiation.
Implementation Method 1
The buffer capacitor and the internal circuit capacitance, together with a high-impedance internal resistance of the supply unit, which is caused by the behavior of the current source, form an RC element with low-pass behavior. Alternatively or additionally, the buffer capacitor and the internal circuit capacitance together with the supply unit can form an LC element, a ferrite bead C element or a combination of the elements mentioned, so that a low-pass behavior is achieved.
Implementation Method 2
a supply unit is provided which is designed in such a way that it has a current source behavior at least at the clock frequency of the integrated circuit
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
In a circuit arrangement (1), to supply an integrated circuit (4) with electrical energy in a reliable, low-radiation manner, a first mass terminal (14) of the integrated circuit (4) is connected to a circuit board mass (3) and an external buffer capacitor (17) is connected to a supply terminal (5) and a second mass terminal (18) of the integrated circuit (4). The arrangement is also equipped with a supply unit (15), which exhibits current source behaviour, at least at a pulse frequency of the integrated circuit (4). The buffer capacitor (17) reduces charge-related voltage fluctuations, the current source behaviour of the supply unit (15) causing a decoupling of the frequency between the charging and discharging process of the buffer capacitor (17). The high-frequency discharge currents are tightly restricted in the circuit arrangement (1), thus preventing significant radiation.