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I have an opto-coupler circuit where is very slow turn off. I can't figure out what is the cause of this problem. It's for UART isolation, with speed 9600 baud. Datasheet: EL357NC Do I have som...
#2: Post edited
by
Chupacabras
·
2024-10-12T16:48:24Z (2 months ago)
- I have an opto-coupler circuit where is very slow turn off.
- I can't figure out what is the cause of this problem.
It's for UART isolation, with speed 9600 baud.- Do I have some error in my schematic?
- Or is actually opto-coupler IC faulty?
- This is schematic:
- 
- This is input signal (METER_RX_IC), which goes from MCU through 220 Ω:
- 
- This is output signal (OPTO_RX_E):
- 
- Opto turns on as expected, but the fall-time is very slow.
- I tried to remove Q301, no change.
- I have an opto-coupler circuit where is very slow turn off.
- I can't figure out what is the cause of this problem.
- It's for UART isolation, with speed 9600 baud.
- Datasheet: [EL357NC](https://en.everlight.com/wp-content/plugins/ItemRelationship/product_files/pdf/DPC-000253_EL121N_Series_Datasheet_rev4.pdf)
- Do I have some error in my schematic?
- Or is actually opto-coupler IC faulty?
- This is schematic:
- 
- This is input signal (METER_RX_IC), which goes from MCU through 220 Ω:
- 
- This is output signal (OPTO_RX_E):
- 
- Opto turns on as expected, but the fall-time is very slow.
- I tried to remove Q301, no change.
#1: Initial revision
by
Chupacabras
·
2024-10-12T06:33:26Z (2 months ago)
Opto-coupler, slow turn off
I have an opto-coupler circuit where is very slow turn off. I can't figure out what is the cause of this problem. It's for UART isolation, with speed 9600 baud. Do I have some error in my schematic? Or is actually opto-coupler IC faulty? This is schematic:  This is input signal (METER_RX_IC), which goes from MCU through 220 Ω:  This is output signal (OPTO_RX_E):  Opto turns on as expected, but the fall-time is very slow. I tried to remove Q301, no change.