Noise tolerance of PDN Design

Q1: When designing PDN, what is the corresponding Noise threshold? Is Min and Max coming in DS (AC Tolerance + VR Accuracy)? Ripple? AC Transient? Or Ripple+AC Transient?

<ANS> recommended Noise threshold = Voltage Regulator ripple allowance + AC Transient

Q2: But for Transceiver, there are Ripple and AC Transient. For non-Transceiver, Ripple and AC Transient are combined together.

<ANS> Yes, correct. Commonly, Transceiver's Voltage Regulator requirement is higher ~1% ripple. The extra margin is transfered to AC transient to make sure the Power delivery can cover the current surge during transceiver's high frequency transitions in user mode.

Q3: Which interval is considered for the corresponding frequency range? 100KHz~2MHz?

<ANS> ftarget should be covering 100KHz to 10MHz. More than that the physical capacitors will not able to cover and this frequency range will be covered by on-die decoupling capacitors.

Q4: What is the corresponding determination of IR Drop? Min and Max in DS?

<ANS> please refer to Table 13 of AN910 for the recommended transient and step load spec. For IR drop you can refer to min and max in DS.

regards,

Farabi