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TPS5420: TPS5420 DC to DC Buck

rsdca
Prodigy 35 points
Part Number: TPS5420

Hey Everybody,

what would be the reasons if I just get 0.8 volt at the output of my EVM tps5420evm-605 !?

Input 12vdc lab power supply with 3 amp current cut\load =15 ohm 20w\ expect to see 3.3 volt by having R_Vsens=R6=31.6k but I see 0.8volt !!!

thanks for any comments

  • 0
    TI__Genius 11085 points
    Please refer to the user's guide of the EVM for www.ti.com/.../slvu163.pdf

    Page 3 of the user's guide mentioned to get 3.3V output voltage, R2 should be 5.9kOhm. I didnot find a R6 in the schematic.

    The reference voltage of the TPS5420 is 1.2V. If you only see 0.8V at the output, it means the regulator is not regulating at all. When the part is regulating, the Vsense pin voltage should be equal to the reference voltage, which is 1.2V. The output voltage should be no lower than that.

    To debug, please measure the voltage at the input pin, make sure the pin is seeing the 12V DC input voltage. Then probe the PH pin voltage, the waveform should be a PWM signal, like shown in Fig 17 and 18 of the datasheet. The peak of the PH pin voltage should be around the VIN voltage. Also make sure the output is not over loaded. Measure the input power supply current, it should be approximately Vout*Iout/Vin.

    Hope these helps.

    -Yang