Tool/software:
Hello -
We are using the DRV8428E to control a pair of latching relays.
We don't need any current chopping. Can we safely tie VREF A and VREF B directly to 1.8V? Or is a resistor in line required, I did not see anything in the datasheet regarding input impedance.
Thanks
Hi Leon,
Thanks for your post.
VREFx pins are fairly high impedance around 50 kΩ. It is okay to connect it directly to a voltage source. A series resistor 1 to 10 kΩ is generally used by designers to limit the current in the event of a short on the pin, for example. This is not a requirement for the device.
That said, you wanted to not have any current chopping. What is the load current expected? There is no way to disable current chopping but setting the VREFx above the maximum load current will result with no chopping. When VREFx = 3 V, the MAX recommended value, current chopping will happen at 1 A as per the calculation. With 1.8 V VREFx the chopping limit would be 600 mA. For load current < 600 mA there will be no current chopping. Thank you.
Regards, Murugavel
Hi Murugavel - thank you for the prompt reply. Expected current is ~100mA per relay.
so to be more clear, in order to protect system if there is pin short, you would recommend connecting 1.8V to 1 to 10kOhm resistor, and then to VREFA/VREFB together.
Like this (dont need separate resistor for each pin).
Thanks
Leon
Hi Leon,
so to be more clear, in order to protect system if there is pin short, you would recommend connecting 1.8V to 1 to 10kOhm resistor, and then to VREFA/VREFB together.
Like this (dont need separate resistor for each pin).
Yes, this should be fine. Thank you.
Regards, Murugavel
