Hi, I'm having trouble with my first attempt at a buck step down circuit. I chose the RT6215EHGJ8F and followed the component choices on page 7 of the attached spec sheet to suit the 5V configuration. The only difference I have is that the enable and mode pins are connected and then a switch connects them to the supply voltage. I've measured that voltage reaching those pins and it's over 3V.

My problem is that the output voltage I'm getting is 0.92V and stays stable at that as the supply voltage increases. Could anyone suggest how best to trouble shoot this?

 

Hello,

My first thought is that the 'mode' pin has a 3.5v zener connected to it. I am not sure what that is for, but i wonder what happens if it blows out due to overvoltage.

What is your power supply voltage?

You may want to supply more details of your current setup too. You have to realize that saying that you are doing everything right but it's still not working does not tell us anything that is needed to know.
Do you happen to have an oscilloscope?

 

Thanks for the reply, while preparing pictures to provide you with more details I realised my very amateur mistake. In the table for the resistors the value for R1 is 107 which I took to be 107 Ohm but the units at the top of the table are kOhm. I will switch to the correct resistor after dinner and hopefully it will work.

 

Thanks for the reply, while preparing pictures to provide you with more details I realised my very amateur mistake. In the table for the resistors the value for R1 is 107 which I took to be 107 Ohm but the units at the top of the table are kOhm. I will switch to the correct resistor after dinner and hopefully it will work.

Hi,

Oh that would make a big difference, provided the chip still works.
I'd still like to know more about that zener diode though and if it blew out because it was connected right to the power supply rail.