**Part Number:**MC34063A

**Other Parts Discussed in Thread:**LM5155, LM5156, LM5158, LM5157

Hello E2E Experts,

Good day.

I am trying to design a circuit using the MC34063A. I need a 5V, 1.5A output using between 7-26V input. I am not good at this sort of thing and I don't quite get the datasheet. I was hoping for assistance in selecting values. due to the chip shortage, a regulator we currently use is not available. I am looking to design a sort of drop-in substitute.

I calculated R1 and R2 easily enough, R1 being 1.2K and R2 being 3.6 or 3.8K, but I don't understand what is determining the output current. The inductor, caps, and output current values are kinda where I am stuck.

I don't know if I need 1.5A, exactly, that's just what the current one does. I know I need 500mA minimum upwards to 1.5A max. If this works, we will probably need a version that's 3.3V out too, but I assume not much beyond R1 and R2 will change.

I need assistance understanding it. I already have the datasheets. I found a bunch of online calculators, but none of them show me how the output current is configured.

Thank you in advance for your support.

Regards,

CSC