Program Atmel MCU

Discussion in 'The Projects Forum' started by bhorobec, Oct 26, 2013.

  1. bhorobec

    Thread Starter New Member

    Oct 26, 2013
    Hi. I am a bit of a beginner when it comes to designing circuits, and I wanted to have someone look over the circuit I built to make sure it will work the way I have planned. I am designing a circuit to power an Ethernet interface chip and an Atmel MCU. Under normal operation, this circuit operates at 3.3V (VCC). However, when the user needs to flash the MCU through the ISP header, the circuit will be powered at either 3.3V or 5V (depending on the programmer used) from ISPVCC. However, the ethernet chip is not 5V tolerant. Therefore, I need to design a simple circuit that disconnects power to the Ethernet chip when the circuit is powered through ISP header. Another problem is that the MCU must be powered at +/- 0.5V of the programming voltage, and therefore I will choose a Schottky diode with a low Vf (<400mV) for D1.

    Link to my schematic:

    So if anyone could shed some light on whether or not this will work for my purposes, I would greatly appreciate it. Thanks.