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LMX1204EVM: DC Supplies and Current Draw

Steve Anthony
Prodigy 50 points
Part Number: LMX1204EVM
Other Parts Discussed in Thread: LMX1204

The EVM used two 1 amp regulators for the LMX1204. One for the VCC01/VCC23 pins and the other for the VCC_CLKIN/VCCLOGICLK pins. The datasheet gives the typical current draw as 1050mA with everything on.

What is the max expected current draw for each one amp supply? Is the thinking that one is for digital circuits and the other analog and they need to be on separate rails?

I will be using two of the LMX1204 chips on one board and it seems like using four 1 amp regulators is overkill.

Thanks in advance.

  • 0
    TI__Guru* 85740 points

    Hi Steve,

    I have seen the current goes up to 1.1A in worst case configuration. 

    The reason we use two LDOs is to minimize the power dissipation on each LDO. Output voltage of the LDO is 2.5V, when input voltage is 3.3V and current flow is 500mA, then the LDO has to eat up 0.4W of power. 

    We can definitely use a 2A LDO for each LMX1204, but we should reduce the input voltage to something around 2.8V in order to reduce the power dissipation.