Kindly any one give the clarification on this.

While going through a DDR Memory data sheet, I have found two (more than that) power supply pins.

What is the necessity of this DLL power supply terminals?

What is the difference between DLL Power supply and Power supply?

NT5TU128M8HE Datasheet


Thanks in advance

  • \$\begingroup\$ Do you understand what the DLL is? \$\endgroup\$
    – Andy aka
    Jan 19 '16 at 13:11
  • \$\begingroup\$ i am not sure. But i am guessing it is Delay locked loop. But i dont know what is the relation between this and Power supply ? \$\endgroup\$
    – Photon001
    Jan 19 '16 at 13:13

Separate power supply pins are provided for the internal logic (VDD), the DLL (VDDL) and the I/O drivers (VDDQ) because it isn't possible to decouple them from each other on the die itself.

Remember, every pin on the package represents a certain amount of series impedance at the speeds at which memory runs. When the DC power is delivered through such an impedance, there isn't much you can do on the chip itself to prevent the large current pulses generated by the I/O drivers from affecting the internal logic. The DLL is particularly sensitive to noise, so it is brought out separately from the rest of the logic.


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