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TCA9406: Relationship between VCCA and VCCB during power-on transient time

Part Number: TCA9406

Hi Team,

It is mentioned in the datasheet that VCCA must be less than or equal to VCCB (except during power-on transient time), do you have a number for the "power-on transient time"?

In my application, VCCA will always be supplied by 3.3V while VCCB will ramp from 0 to 3.3V at system power-up, also OE is being pulled high to VCCB. We're worried after OE reaches 2.145V (0.65*VCCA) there may be some issue as VCCA will be larger than VCCB during VCCB ramps from 2.145V to 3.3V. So we're thinking if the ramp-up time falls within the "power-on transient time" then that should be OK. 

Please let me about know your thoughts.

Thanks!

Roy

  • Hi Roy,

    As long as you are operating within the Absolute Maximum ratings you can not do any permanent damage to the device, the device just may not function as you intend. In this case when VCCA is larger than VCCB during power up you may see some glitches in the level translation is you start sending data. But as long as you wait for VCCB to reach 3.3V to start sending data then you should see no issue with the device.

    Best,

    Chris