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[SOLVED] FT232RL, entegrated LDO 3V3 regulator using PROBLEM

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elt42at

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HELLO TO EVERYONE!

I tried to use, BUS POWERED USB to UART with FT232RL. The design is so simple but, MY 3.3V output is over 4.2V. So, i re-solder 3V3 and VCCIO pins from PCB. I measured with AVO meter. The LDO output pin (3V3) is 3,26V. IT is OK! But THE VCCIO pin seems 4.4V!!!!!!

I soldered 3V3 pin to PCB, The VCC which goings to MCU VCC is about 3.3V. IT is ok!

Now, I have to solder the VCCIO pin to use FTDI FT232RL UART module in LVTTL 3.3V. I have to use VCCIO pin :D :D :D

I don't understand that, WHY an input (power input pin) makes the LDO output up to 4.2volt ????

I only use FT232RL pins RX,TX,CTS,RTS and CBUS0 and CBUS1 as RX/TX leds and CBUS2 as MCU reset, and CBUS3 MCU interrupt!!!

Please help me about that! I can't get integrated 3V3 output in the voltage 3.3V when i solder the VCCIO pin. It goings to 4.2V. Free un-soldered VCCIO pin seems over 4.4V. But it is an input pin !!!!

Thanks for your answers!
 

Hi,
try adding decoupling capacitors(10micro and 0.1micro farad) at the supply and VCCIO pins.looks like there is some noise issues

---------- Post added at 14:32 ---------- Previous post was at 14:16 ----------

HI,

refer the image, vbus is 5v

 

YES, my schematics like that expect, my 3V3_LDO and VCCIO pins connected together! MY FTDI is working, UART working.... THE PROBLEM IS THAT WHEN VCCIO AND 3V3_OUT together, I measure 4.2V. When i re-solder VCCIO pin, The voltage is 3.25. I see 4.4V on VCCIO pin when it is free!!
 

Voltage is perfect! I pick-up VCCIO pin to free by re-soldering. The 3V3 is about 3.26V (fix)
I re-solder all pull-up resistors. Also, now there is 4.4V on VCCIO pin :S
 

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