“In electrical systems, ICs rely on decoupling capacitors to maintain a stable supply voltage. They are usually placed near the IC to stabilize the voltage on the IC’s power supply pins or on the output of a regulator to provide transient currents such as those required during IC startup or wake-up.
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In electrical systems, ICs rely on decoupling capacitors to maintain a stable supply voltage. They are usually placed near the IC to stabilize the voltage on the IC’s power supply pins or on the output of a regulator to provide transient currents such as those required during IC startup or wake-up.
These capacitors can range in value from 100 nF to 100 µF, but larger capacitors may be required if the supply voltage drops too much or is completely interrupted. These capacitors can be 500 µF or larger and are called storage capacitors because they store and provide enough energy to maintain operation in the event of a mains power interruption.
ON semiconductor‘s NCV7356 is a single-wire CAN transceiver that provides the physical layer for communication using the CAN protocol. In a car, the power supply (Vbat) can drop from the nominal 13.8 V to 6 V, or even 4V. In this case, a storage capacitor can be used to maintain a storage circuit or other device connected to Vbat, as shown in Figure 1. The extra capacitors are not meant to power the NCV7356 in operation, but to keep the device in a recessive state or sleep mode. However, in some cases, adding this storage capacitor can cause damage to the NCV7356. Specifically, a GM test requirement simulates a blown fuse that could cause damage to the NCV7356.
Recommended capacitance when Vbat_ecu > 1.0µF (not affected by ISO7637/1 test pulse)
ON Semiconductor provides application note AND8258/D which provides more details on test conditions and possible solutions. The three solutions include adding a reverse protection diode, adding a series resistor to the storage capacitor, and adding a series resistor to the storage capacitor and a parallel diode. Each solution offers different levels of performance and cost, and it is up to the designer to determine which is most appropriate and meets the requirements of the intended application.
The Links: 7MBI100U4S-120 CM150DC1-24NF
