TMS320F28379D: Digital inputs and outputs

electrocc

Part Number: TMS320F28379D
Other Parts Discussed in Thread: SN74LVC1G07

Hi,

I want to drive a relay (needs around 20mA for the control input) with a GPIO of the microcontroller. Except a transistor or an optocoupler, is there a circuit I can put between my microcontroller and the relay to increase the current to drive the relay ?

Other question, what kind of circuit do you have to convert a digital signal 0-5V to a 0-3,3V ?

Thank you

over 4 years ago

0 Wang5577 over 4 years ago

TI__Guru 56650 points

Electrocc,

20mA load is too small for our motor driver products. I would think a small transistor could work.

What is the initial status of that relay, or the power up sequence? If the mircrocontroller and GPIO was powered up, but, relay circuit has been powered up, do you want to see the 20mA or 0mA? You can put a NFET or a PFET switch between the relay and the ground to control the relay; and put a 100kohm resistor between the FET's gate to ground. The FET gate is controlled by the mircrocontroller GPIO. A NFET or PFET is related to the initial status setting.

0 electrocc over 4 years ago in reply to Wang5577

Expert 2450 points

Hi Wang5577,

When everything will be powered up, I want to see 0mA on the relay, so do I need to put a NFET or a PFET ? Do you have a product example ?
For my application, is it better to use a JFET or MOSFET ?

For the other question, do you have any idea ?

Electrocc said:

Other question, what kind of circuit do you have to convert a digital signal 0-5V to a 0-3,3V ?

Thank you,

0 Wang5577 over 4 years ago in reply to electrocc

TI__Guru 56650 points

Eletrocc,

We cannot give the system detail design if it is not related to our device. You can read some textbooks or google for it.

To clarify my first post's idea, I just draw the circuit.

BTW, you can use a resistor divider to convert a digital signal 0-5V to a 0-3,3V.

0 Wang5577 over 4 years ago in reply to electrocc

TI__Guru 56650 points

Eletrocc,

We cannot give the system detail design if it is not related to our device. You can read some textbooks or google for it.

To clarify my first post's idea, I just draw the circuit.

BTW, you can use a resistor divider to convert a digital signal 0-5V to a 0-3,3V.

0 electrocc over 4 years ago in reply to Wang5577

Expert 2450 points

Hi Wang,

The relay needs around 15mA for 5V or 20mA for 3,3V.
Please find the wiring diagram :

Do I need to use a flyback diode between pins 3 and 4 ?

I want to use one of your transistor, that's why I asked you for a component reference.

Is the scheme correct ?

Regards

0 Wang5577 over 4 years ago in reply to electrocc

TI__Guru 56650 points

Eletrocc,

We are on the same page. What is the relay device part number? Would you post a question on that device about how to drive it?

0 electrocc over 4 years ago in reply to Wang5577

Expert 2450 points

The relay is not a Texas device, but it's not very important.

I just want to have a (Texas) transistor part number which can drive 15mA for 5V or 20mA for 3,3V with a Vgs = 3,3V

I found a lot of NFET but I think they are not appropriate with my application, because I don't need a power transistor.

Regards,