THS3470: Power Supply Sequencing and Slew Rate Requirements

Hi Andy,

For the power supply sequencing, in an ideal scenario, ramping your supplies symmetrically would be best. This is because there are internal nodes that are tied to certain supplies that use mid supply as a reference. If one supply is on while the other is still off, you could cause transistors to get damaged. However, there will always be some kind of asymmetry but as long as the supplies are relatively close as they rise together the device should be fine. Regarding the slew rate of the supplies, we would recommend 1V/us max.

Best Regards,

Ignacio

Ignacio,

We're using a +/-25V bipolar supply. The positive and negative supplies are well-matched once they have settled.  However, they do not rise together. The positive supply rises faster than the negative.

What imbalance can the THS3470 tolerate? 

Does the power-down mode offer any protection in this case?  That is, would it help if we power down the op amp until the supplies have both settled?

Thanks!

Andy

Hi Andy,

I was able to ask our team, and we believe 5V would be tolerable for the part.  Regarding the power down, there is still a lot of circuitry that is turned on when in power-down which is why the quiescent current is still 14mA so I am not sure if this would do much for the device as it is ramping up if the supplies are really asymmetric.

Best Regards,

Ignacio