Power supply for LM3S

[neil84]

Hi all,

I have two question about lm3s8962 board.

I'm going to integrate it in my custom controller board so I'd like to know if it is possible to power it thru pins 33-34 and not thru USB port.

I have to control 6 DC motors, so I need to use the 6 PWM outputs. However 1 PWM is connected to the buzzer. according to the datasheet there is some jumpers that allows disconnecting some peripherals. I didn't view any think like that.

Thanks

[NicB]

There are two PWMs wired on board (buzzer and LED). The buzzer is actually driven by a MOS-FET. If the sound noise is not so annoying for you and the gate capacitance don't disturb the external hardware you can leave the jumpers/resistors on board:

Of course, you can power the board externally as you described. Be aware about maximum current sourced/sunk by PWM pins (hopping you don’t connect those motors directly:)

[NicB]

I forgot to mention PWM4 and PWM5 which are wired to UP/DOWN buttons - you should not press the buttons without removing appropriate resistors/jumper! (the microcontroller output might give-up first when it shorted to ground through the button:)

However, you can find more about used pins on page 32 (I/O Breakout Pads) and, of course, schematics.

[neil84]

That's strange.

On my board I have no resistors:

 

 The buzzer makes noise that's why I'd like to disconnect it.

[NicB · Accepted solution]

No it is not strange - neither my boards have resistors (that picture was from the datasheet).

Zero Ohms resistors could be a simple tracks which are lowering the cost.

Just cut the tracks - it is even simpler than unsoldering.