MSP-TS430PN80USB: What is purpose of the D2 and D3 diodes?

If they are not assembled on original board then they are not mandatory, right? After all you are building custom board - so you are in charge to define which components are needed and which are not. 

Ilmars said:

If they are not assembled on original board then they are not mandatory, right? After all you are building custom board - so you are in charge to define which components are needed and which are not. 

In fact, they are do. That's why I am asking. I am referencing the SLAU278P document page 99.

Gaby Heifets said:

I am referencing the SLAU278P document page 99.

If you (your application) need those LED's - put them on board. If you don't need them - don't put them on board. If you are not sure - put them on board with jumpers as in original circuit, later will see you use them or not. What's the problem?

I am talking about ll103A Shotky diodes. Once again D2 and D3. D2 placed after the USB VBUS entry signal. The second one placed on the JTAG power signal. Most likely they are placed to avoid back current from the MSP430, but I haven't find any reference for that.

Have you referred to the document I posted?

Thanks

Got it. Now this makes things clear.To avoid a conflict between the JTAG power rail and the USB VBUS.

Thanks!

The diodes are listed on page 102.

An USB-Slave should not supply power to the bus. But since this board can be external powered the diode blocks outgoing power. Normally isn’t necessary.

Pin 2 of the JTAG is the 3V supply voltage from the JTAG and for the same reason (external power) this diode. Pin 4 can be used as supply to JTAG.

If the board connected to an external power supply, what is the VBUS pin status?

If you don’t need USB power, leave the pin unconnected.