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Q&A Does My Circuit Contain High-Speed Signals?

My circuit includes the following components: • PIC16 with internal clock, frequency: 32 MHz • ST LED2000 LED driver (a buck converter) with a PWM dimming input. The converter itself isn't a conc...

2 answers  ·  posted 1mo ago by Eyal78‭  ·  last activity 1mo ago by TonyStewart‭

Question PCB high-speed pcb-layout layout
#4: Post edited by user avatar Eyal78‭ · 2025-02-06T17:50:41Z (about 1 month ago)
  • My circuit includes the following components:
  • • **PIC16** with internal clock, frequency: 32 MHz
  • • **ST LED2000** LED driver (a buck converter) with a **PWM dimming input**
  • • **TI BQ24070RHL** battery charger
  • • **LED controlled via PWM** by the microcontroller.
  • **My question:**
  • Do the following signals qualify as high-speed?
  • I’m asking this to determine whether I need to ensure a **proper return path** for them and/or maintain **large spacing** between them.
  • If not, can I ignore the return path considerations?
  • **Key signals I believe require attention:**
  • 1. **Charger outputs** – These are open-drain outputs. These outputs are connected to the microcontroller inputs (with internal PU). I couldn't find rise/fall time specifications in the datasheet.
  • 2. **PWM outputs from the microcontroller** – Base frequency: 200–500 Hz.
  • One output goes to the LED driver (possibly with or without a pull-down resistor).
  • Another output drives an LED.
  • 3. **Push button** with a pull-down resistor, connected to a microcontroller input.
  • My circuit includes the following components:
  • • **PIC16** with internal clock, frequency: 32 MHz
  • • **ST LED2000** LED driver (a buck converter) with a **PWM dimming input**. The converter itself isn't a concern regarding this question. I mentioned it only to give a clue for the PWM signal destination.
  • • **TI BQ24070RHL** battery charger
  • • **LED controlled via PWM** by the microcontroller.
  • **My question:**
  • Do the following signals qualify as high-speed?
  • I’m asking this to determine whether I need to ensure a **proper return path** for them and/or maintain **large spacing** between them.
  • If not, can I ignore the return path considerations?
  • **Key signals I believe require attention:**
  • 1. **Charger outputs** – These are open-drain outputs. These outputs are connected to the microcontroller inputs (with internal PU). I couldn't find rise/fall time specifications in the datasheet.
  • 2. **PWM outputs from the microcontroller** – Base frequency: 200–500 Hz.
  • One output goes to the LED driver (possibly with or without a pull-down resistor).
  • Another output drives an LED.
  • 3. **Push button** with a pull-down resistor, connected to a microcontroller input.
  • [Battery Charger datasheet](https://www.ti.com/lit/ds/symlink/bq24070.pdf?ts=1738837513670)
  • [LED driver](https://www.st.com/resource/en/datasheet/led2000.pdf)
  • [PIC16F18446 Microcontroller](https://www.microchip.com/en-us/product/pic16f18446)
#3: Post edited by user avatar Olin Lathrop‭ · 2025-02-04T18:35:29Z (about 1 month ago)
Enough with the annoying fluff! This is now the second time I had to edit it out. Read the rules already!
  • My circuit includes the following components:
  • • **PIC16** with internal clock, frequency: 32 MHz
  • • **ST LED2000** LED driver (a buck converter) with a **PWM dimming input**
  • • **TI BQ24070RHL** battery charger
  • • **LED controlled via PWM** by the microcontroller.
  • **My question:**
  • Do the following signals qualify as high-speed?
  • I’m asking this to determine whether I need to ensure a **proper return path** for them and/or maintain **large spacing** between them.
  • If not, can I ignore the return path considerations?
  • **Key signals I believe require attention:**
  • 1. **Charger outputs** – These are open-drain outputs. These outputs are connected to the microcontroller inputs (with internal PU). I couldn't find rise/fall time specifications in the datasheet.
  • 2. **PWM outputs from the microcontroller** – Base frequency: 200–500 Hz.
  • One output goes to the LED driver (possibly with or without a pull-down resistor).
  • Another output drives an LED.
  • 3. **Push button** with a pull-down resistor, connected to a microcontroller input.
  • Thanks in advanced for any answer,
  • Eyal
  • My circuit includes the following components:
  • • **PIC16** with internal clock, frequency: 32 MHz
  • • **ST LED2000** LED driver (a buck converter) with a **PWM dimming input**
  • • **TI BQ24070RHL** battery charger
  • • **LED controlled via PWM** by the microcontroller.
  • **My question:**
  • Do the following signals qualify as high-speed?
  • I’m asking this to determine whether I need to ensure a **proper return path** for them and/or maintain **large spacing** between them.
  • If not, can I ignore the return path considerations?
  • **Key signals I believe require attention:**
  • 1. **Charger outputs** – These are open-drain outputs. These outputs are connected to the microcontroller inputs (with internal PU). I couldn't find rise/fall time specifications in the datasheet.
  • 2. **PWM outputs from the microcontroller** – Base frequency: 200–500 Hz.
  • One output goes to the LED driver (possibly with or without a pull-down resistor).
  • Another output drives an LED.
  • 3. **Push button** with a pull-down resistor, connected to a microcontroller input.
#2: Post edited by user avatar Eyal78‭ · 2025-02-04T10:41:53Z (about 1 month ago)
  • My circuit includes the following components:
  • • **PIC16** with internal clock, frequency: 32 MHz
  • • **ST LED2000** LED driver (a buck converter) with a **PWM dimming input**
  • • **TI BQ24070RHL** battery charger
  • • **LED controlled via PWM** by the microcontroller.
  • **My question:**
  • Do the following signals qualify as high-speed?
  • I’m asking this to determine whether I need to ensure a proper return path for them and/or maintain large spacing between them.
  • If not, can I ignore the return path considerations?
  • Key signals I believe require attention:
  • 1. Charger outputs – These are open-drain outputs. These outputs are connected to the microcontroller inputs (with internal PU). I couldn't find rise/fall time specifications in the datasheet.
  • 2. PWM outputs from the microcontroller – Base frequency: 200–500 Hz.
  • One output goes to the LED driver (possibly with or without a pull-down resistor).
  • Another output drives an LED.
  • 3. Push button with a pull-down resistor, connected to a microcontroller input.
  • Thanks in advanced for any answer,
  • Eyal
  • My circuit includes the following components:
  • • **PIC16** with internal clock, frequency: 32 MHz
  • • **ST LED2000** LED driver (a buck converter) with a **PWM dimming input**
  • • **TI BQ24070RHL** battery charger
  • • **LED controlled via PWM** by the microcontroller.
  • **My question:**
  • Do the following signals qualify as high-speed?
  • I’m asking this to determine whether I need to ensure a **proper return path** for them and/or maintain **large spacing** between them.
  • If not, can I ignore the return path considerations?
  • **Key signals I believe require attention:**
  • 1. **Charger outputs** – These are open-drain outputs. These outputs are connected to the microcontroller inputs (with internal PU). I couldn't find rise/fall time specifications in the datasheet.
  • 2. **PWM outputs from the microcontroller** – Base frequency: 200–500 Hz.
  • One output goes to the LED driver (possibly with or without a pull-down resistor).
  • Another output drives an LED.
  • 3. **Push button** with a pull-down resistor, connected to a microcontroller input.
  • Thanks in advanced for any answer,
  • Eyal
#1: Initial revision by user avatar Eyal78‭ · 2025-02-04T10:37:06Z (about 1 month ago) 
Does My Circuit Contain High-Speed Signals?
My circuit includes the following components:

•	**PIC16** with internal clock, frequency: 32 MHz

•	**ST LED2000** LED driver (a buck converter) with a **PWM dimming input**

•	**TI BQ24070RHL** battery charger

•	**LED controlled via PWM** by the microcontroller.



**My question:**

Do the following signals qualify as high-speed?

I’m asking this to determine whether I need to ensure a proper return path for them and/or maintain large spacing between them.
If not, can I ignore the return path considerations?

Key signals I believe require attention:

1.	Charger outputs – These are open-drain outputs. These outputs are connected to the microcontroller inputs (with internal PU). I couldn't find rise/fall time specifications in the datasheet.
2.	PWM outputs from the microcontroller – Base frequency: 200–500 Hz.

One output goes to the LED driver (possibly with or without a pull-down resistor).

Another output drives an LED.

3.	Push button with a pull-down resistor, connected to a microcontroller input.


Thanks in advanced for any answer,

Eyal
PCB high-speed pcb-layout layout