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TCA9803: Using same supply rail on VCCA and VCCB

Venugopal_S
Prodigy 135 points

Part Number: TCA9803
Other Parts Discussed in Thread: ISO1540

Hi,

We are planning to use TCA9803 between MPU and a I2C isolator (ISO1540) in one of our applications. The main purpose being to add sufficient margins on the voltage levels (Vil of MPU is currently exactly same as the Vol of isolator).

This is the sequence of devices

MPU -- {TCA9803 (SideB) -- TCA9803 (Side A)} -- {ISO1540 (Side 1) -- ISO1540 (Side 2)} -- SMBus device

Question is : Are there any complexities in shorting VCCA and VCCB pins of TCA9803 and connecting them to the same 3.3V supply rail? 

  • 0
    Guru 324330 points

    The worst-case VOL is seen only at the highest current. But I did not find any information in the ISO1540 datasheet that would allow to estimate how much VOL could be reduced.

    Anyway, section 11 of the TCA9803 datasheet says:

    VCCA may be greater than, less than, or equal to VCCB. Each supply has its own requirement of voltage range, but there is no required relationship between VCCA and VCCB values.