N58 Hardware User Guide
Chapter 5 Application Interfaces
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As there is a big difference between the power input and VBAT, DC-DC should be selected for
higher efficiency, and the maximum output current should be at least 2.5 A.
When DC-DC is selected, it is recommended that the switching frequency be greater than or
equal to 500 kHz. The power inductor is associated with the setting of the switching frequency.
Note that the switching frequency of DC-DC is related to the performance of the whole device,
and may cause EMC interference.
For vehicle batteries (lead-acid batteries), power surge protection must be added to the input
front end, and the component withstand voltage must be greater than 42 V.
Place C7 close to the module. A large-
capacity aluminum electrolytic capacitor (470 μF or 1000
μF) or tantalum electrolytic capacitor (220 μF or 100 μF) can be selected to improve the
instantaneous large current freewheeling capability of the power supply. Its withstand voltage
must be greater than 2 times the voltage of the power supply.
Place low-ESR bypass capacitors (C9, C10, C11, and C12) close to the module to filter out high-
frequency interference from the power supply.
PCB Layout
An ESR capacitor must be placed at the output end of the power supply to suppress the peak current.
A TVS diode must be placed at the power input end to suppress voltage spikes and protect back-end
components. The circuit design is important, and the component layout and traces are also important.
Several key points in power supply design are summarized below:
The TVS can absorb instantaneous high-power pulses, and withstand instantaneous pulse
current peaks up to tens or even hundreds of amperes. The clamp response time is extremely
short. TVS should be placed as close to the interface as possible. This is to ensure that the
surge voltage can be clamped before the pulse is coupled to the adjacent PCB wires.
The bypass capacitor must be placed close to the power supply pin of the module to filter out
high-frequency noise signals in the power supply.
For the main power loop of the module, the PCB trace width must ensure that the 2.5 A current
can be passed safely, and there should be no obvious loop voltage drop. The PCB trace width
should be at least 2.5 mm to ensure that the ground plane of the power supply part is as
complete as possible. Ensure that the power cable is short and thick.
Noise-sensitive circuits, such as audio circuits and RF circuits, must be kept away from power
circuits, especially when the DC-DC power supply is used.
Ensure that the loop is minimized because the SW pin voltage frequency of DC-DC power
supply is relatively high. Sensitive components must be kept away from the SW pins of DC-DC
components to prevent noise coupling; feedback components must be placed as close to the FB
pin and COMP pin as possible.
The GND pin and bottom pad of the chip must be grounded to ensure good heat dissipation and
noise isolation.
