Do I require flyback diode while driving relay with ULN2003..?

I am trying to drive 4 relays with Atmega328 via the ULN2003.
Please, someone, tell me if it's necessary to use a flyback diode on the relays as I am using the ULN2003.

If you consult the datasheet it will show you that it has built-in diodes, you need to ensure the COM
pin is connected to your supply so the diodes are in circuit. Thus if all the relays share the same supply
just connect the COM pin to the supply +ve.

The chip was designed specifically for driving lots of relays, which is why its still made today as vast
amounts of old equipment still have them in sockets on their relay boards. The designers of chips are
smart.

MarkT:
If you consult the datasheet it will show you that it has built-in diodes, you need to ensure the COM
pin is connected to your supply so the diodes are in circuit. Thus if all the relays share the same supply
just connect the COM pin to the supply +ve.

The chip was designed specifically for driving lots of relays, which is why its still made today as vast
amounts of old equipment still have them in sockets on their relay boards. The designers of chips are
smart.

Yes.. I have a COM 12V positive for all the relays.
SO you are saying there is no nessecity for a flyback doide externally..
The doides inside will do the same job.

That's what they're there for.

runaway_pancake:
That's what they're there for.

Ok .. Copy that..
Thanks for clearing my doubts..

There's also a similar chip, the ULN2803 with 8 channels rather than 7, ideal for driving from 8-bit shift
registers such as the 74HC595. Its 18 pin which is a little unusual though.

MarkT:
There's also a similar chip, the ULN2803 with 8 channels rather than 7, ideal for driving from 8-bit shift
registers such as the 74HC595. Its 18 pin which is a little unusual though.

Wonderful..
thanks for that information. I will surely keep that noted..
Might need someday.

Mind you, the TPIC6B595 combines the shift register with eight FET drivers and does not have the voltage drop or heat production of the mostly obsolete ULN2x03 so it would be suitable for driving 5 V as well as 12 V relays.

It also incorporates the "flyback" protection internally using Zeners.

But 50V zener protection means much more EMI back to the circuit driving it, compared to free-wheel diodes,
so I'd recommend using external diodes with that chip unless the relay coil voltage is already 36V or 48V.

If you're driving 5 or 12V relay coils, allowing 50V spikes is considerably more noisy than capping them at the
low voltage. Inductive spikes aren't just a problem through causing damage.