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PSoC 5, 3 & 1 MCU

user_3716231
New Contributor II

i connect cy8ckit-059 to my laptop through kitproUSB and i measure its pin VDD ,the value is 4.86V not 5V.

i have already set 5V in my .cydwr system ,but the result is still the same.

could someone please tell me how can i make it provide 5V except using external power supply?

best regard,

sean.

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1 Solution
Len_CONSULTRON
Honored Contributor II

sean,

It's simple.  If you look at the schematics for the cy8ckit-059 you will notice a schottky diode D1 on the KitProg board.

pastedImage_0.png

VBUS is connected directly to the 5V source from the USB cable from the host computer.  VTARG is the voltage directly connected to the PSoC5LP target CPU.  The Schottky diode drop is about 0.1V to 0.3V (depends on the load current.  Higher load currents have a higher drop voltage.)  Therefore in your case, the diode drop is about 0.15V to provide you with 4.85V.  The info I spotted on the internet that the source voltage variation can be from 4.75V to 5.5V.  This is without the D1 voltage drop.

May I ask why a 5V accuracy is needed?

If this is because you are using the 5V supplied to VDDA for use with the ADC vref, I recommend using the internal bandgap vref instead.  This bandgap vref is virtually immune from VDDA (or VDDD) voltage variances.  It is significantly more stable.

Len

Len
"Engineering is an Art. The Art of Compromise."

View solution in original post

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1 Reply
Len_CONSULTRON
Honored Contributor II

sean,

It's simple.  If you look at the schematics for the cy8ckit-059 you will notice a schottky diode D1 on the KitProg board.

pastedImage_0.png

VBUS is connected directly to the 5V source from the USB cable from the host computer.  VTARG is the voltage directly connected to the PSoC5LP target CPU.  The Schottky diode drop is about 0.1V to 0.3V (depends on the load current.  Higher load currents have a higher drop voltage.)  Therefore in your case, the diode drop is about 0.15V to provide you with 4.85V.  The info I spotted on the internet that the source voltage variation can be from 4.75V to 5.5V.  This is without the D1 voltage drop.

May I ask why a 5V accuracy is needed?

If this is because you are using the 5V supplied to VDDA for use with the ADC vref, I recommend using the internal bandgap vref instead.  This bandgap vref is virtually immune from VDDA (or VDDD) voltage variances.  It is significantly more stable.

Len

Len
"Engineering is an Art. The Art of Compromise."

View solution in original post

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