TPS73801 output voltage too low

Ed Saunders

I have a TPS 73801 with a 10 MicroFarad on the input. The enable is connected to the input voltage. R2 is a 1.3kilo Ohm, R1 is 590 ohms. I have 9.12volts coming in and the resistors should limit the outgoing voltage to 7.77volts. The measured voltage is 3.87 voltage on the output side. I had to solder 4" leads to the terminals for use on my breadboard. Do you think I may have fried the voltage regulator. Any clue as to why my voltage is so low. Thank you.

over 8 years ago

0 Aleksandras_Kaknevicius over 8 years ago

TI__Genius 15710 points

Hi Ed,

Based on the below equation, you are actually setting the output voltage to 3.88V.

VOUT = 1.21V * (1 + R1/R2) + IFB * R2

VOUT = 1.21V * (1+ 1300Ω / 590Ω) + 0.000003A * 1300Ω

VOUT = 3.876V + 0.0039V

VOUT = 3.88V

For an output voltage of about 7.77V, an R2 of 240Ω should be used. Let me know if this answers your questions.

Thanks,

Alek Kaknevicius

0 Ed Saunders over 8 years ago in reply to Aleksandras_Kaknevicius

Prodigy 20 points

Alek, thank you so much. That was exactly it. I fortunately had a 240 ohm resistor laying around. Thank you again.

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TPS73801 output voltage too low