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How connecting the voltage feedback of UCD9244 if UCD74120 is powered for two loads?

Feng
Expert 2985 points
Other Parts Discussed in Thread: UCD9244, UCD74120

Hi TI experts,

As usual, one UCD9244 channel connects with one UCD74120 and then generates one regulated voltage for one payload showing in Figure 1.

But I want to implement like Figure 2

So my questions are

a) Choose which one to feedback to UCD9244?VCC or VCCP1 or VCCP2?
b) If VCC should be feedback to UCD9244, the differential routing for VCC and GND would be a problem. Because VCC is originated from Bead and GND is originated from the Payload GND pin, they can not be routing as differential signals from their own origanls.
c) If VCCP1(or VCCP2) should be feedback to UCD9244, the changes from VCCP2(or VCCP1) can be ignored?

Regards

Feng

  • 0
    TI__Genius 9845 points

    It depends on which node requires tight regulation. The impedance between the three nodes are relatively low, so the fluctuation on other nodes will still be sensed, but with a small delay. However, if there are differences in ground potential, the nodes that are far from the sensing point may have a steady state error.

    Therefore, if none of the loads require tight regulation, I would sense VCC, and place the two loads very close to VCC to minimize trace impedance and ground potential difference. If one of the loads require tight regulation, I would sense that node, and put the other load close by. If both nodes require tight regulation, I would use two rails.