Contents
Why do you need high speed SPI routing?
High speed SPI layout routing helps achieve faster data transfer between microcontrollers and peripherals. Avoid suboptimal design with these tips. PCB Design & Analysis
What is the SPI layout of a microcontroller?
This is where the SPI layout comes into play. The serial parallel interface or SPI layout can be defined as the routing of traces between a microcontroller and a peripheral component or device. The layout includes separate data lines, a clock line and a control or select line.
How does a Serial Peripheral Interface ( SPI ) work?
Introduction. Serial Peripheral Interface (SPI) is an interface bus commonly used to send data between microcontrollers and small peripherals such as shift registers, sensors, and SD cards. It uses separate clock and data lines, along with a select line to choose the device you wish to talk to.
What should be included in a SPI layout?
Your SPI traces are not differential pairs; however, treating them as such is advantageous for your SPI layout design. In particular, having data transfer lines of the same length, copper weight and impedance are recommended. For high frequency transmission, consistent impedance is critical for the best signal integrity.
Which is better SPI or Serial Peripheral Interface?
A better approach is synchronous data transmission using a serial peripheral interface or SPI. For your SPI to be most effective, there are considerations aside from timing that must be considered. Let’s take a look at how to optimize high speed SPI layout routing.
Are there magnetic fields on a SPI line?
Your traces are reasonably short and your SPI signals are all actively driven (not open-collector, floating, or passive pull-up). So in that regard I don’t anticipate a problem. Magnetic fields may be a problem. Consider 200pF load on any SPI line. Assume 5 volts in 10 nanoseconds. Using
What is the resistor of a PCB signal bus?
At the driver, in series with the signal, is a simple resistor of around 25 to 75 ohms. The exact value of this resistor has been calculated to match the impedance of the trace minus the source impedance of the driver. So if my trace is 50 ohms, and the driver has a 20 ohm output impedance then my resistor will be 30 ohms, +/- 10%.
How is the trace impedance of a PCB calculated?
The trace impedance can be calculated using the various formulas for “stripline” and “microstrip” traces (Google those). I normally target a 50 ohm trace impedance, and vary the trace width to get that. The signal layer of the PCB needs to be really close to the plane, otherwise the trace needs to be unrealistically wide.
What should copper weight be for high speed SPI?
In particular, having data transfer lines of the same length, copper weight and impedance are recommended. For high frequency transmission, consistent impedance is critical for the best signal integrity.