Having fun with the SY8083P

synchronous step-down DC-DC converter | 2020-06-28, 23:12:00

Some months ago, I was looking for a cheap and reliable step-down DC-DC regulator that I could toy around with in battery-powered circuits and I came across the SY8083PFCC.

Reading the datasheet, it seems to be a very straight-forward and efficient regulator.

The chip comes in a SOIC8 package (called SO8Exposed in the datasheet), with a heat-dissipation pad that keeps the chip cool, given it's small Rdson of only 0.1 ohm.

Do note that there are two switches to calculate the Joule heating for, since it's a synchronous regulator.

It comes unbranded, stamped with a serial number.

Making a working circuit

I design my circuits using Eagle, version 8.

You can design the footprint for this chip or download my personal library.

Now, you only have to route three resistors, three capacitors, an inductor and align them with the chip itself.

Your schematic should have:

-input pin (2) connected with enable (7);

-powergood (8) left floating since it's not implemented;

-feedback (5) connected with the resistor divider and the refreshing capacitor (read the datasheet thoroughly);

-an input (2) and output filter capacitor;

-the inductor's output (3) connected with the voltage divider and filter capacitors.

There's an insert surge filter I'm using at the input, which might come in useful if you don't use physical switches.

As for the circuit, this is the one I've routed. It's part of a larger board that I've cut out.

My personal choice is a 2.2uH inductor with an input capacitor of 10uF and 47uF output filter in order to handle sudden load peaks.

This is what my PCB looks like:

How do I set the output voltage/calculate the resistors?

The datasheet specifies the formula of "Vout=0.6*(1+R1/R2)" and

I've used an 1Mohm resistor for R1 and 215Kohm for R2, targeting 3.3V and expecting there might be some error margin.

Have fun!

You might find out that leaving the output open, with no load at all, might have a 40-50mA consumption while even under the slightest load it'll pull only a few hundred nA. You might note as well some voltage swings, load transients, when switching between light and heavy loads, some 30mV +-.

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