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Lixiaojuan
Level 1
5 sign-ins First reply posted First question asked
Level 1

Hello, 

I am juan, I am using TC234 for designing. VDDM is supplied by 5V from TLF35584 directly, and VAREF is supplied by VDDM passing through a bead, now I removed this bead which means VDDM can not supply  for VAREF,but I measured around 3.9 volts voltage at VAREF while VDDM was 5V. I fell confused, why is there a voltage at VAREF when there is no external supply for it?  Could you please give me some advices or some instructions?

thank you in advance.

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4 Replies
TBencher
Level 5
First like given 50 sign-ins 10 solutions authored
Level 5

Hi,

did you use one of the dedicated Application boards or starter kits? If not please provide your schematics.

Best regards,

TBencher

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Lixiaojuan
Level 1
5 sign-ins First reply posted First question asked
Level 1

Hi,

my schematic is as below:

Lixiaojuan_0-1659081645720.png

there is a L401 between 5V_ADC power supply and VAREF pin originally,but I found there is still 3.9 volts at VAREF after removing L401.

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TBencher
Level 5
First like given 50 sign-ins 10 solutions authored
Level 5

Hi thanks for your schematics,

if you powered up your board with L401 connected and try to measure voltage level without it afterwards, your capacitors could be still charged, which could be the reason for your findings.

Best regards,

TBencher

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TBencher
Level 5
First like given 50 sign-ins 10 solutions authored
Level 5

Hi,

so you should also disconnect the two capacitors from the power branch and repeat your measurement.

Best regards,

TBencher

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