ORLI10G datasheet(33/72 Pages) AGERE

33 / 72 page

Agere Systems Inc.

Data Sheet

October 2001

10 Gbits/s, and 12.5 Gbits/s Line Interface FPSC

ORCA ORLI10G Quad 2.5 Gbits/s

Line Interface Circuit Specifications

Power Supply Decoupling LC Circuit

The 622 MHz—850 MHz line interface macro contains both analog and digital circuitry. The line interface function,

for example, is implemented as primarily a digital function, but it relies on a conventional analog phase-locked loop

to provide its divided clocks. The internal analog phase-locked loop contains a voltage-controlled oscillator. This

circuit will be sensitive to digital noise generated from the rapid switching transients associated with internal logic

gates and parasitic inductive elements. Generated noise that contains frequency components beyond the band-

width of the internal phase-locked loop (about 3 MHz) will not be attenuated by the phase-locked loop and will

impact bit error rate directly. Thus, separate power supply pins are provided for these critical analog circuit ele-

ments.

Additional power supply filtering in the form of an LC pi filter section will be used between the power supply source

and these device pins as shown in Figure 16. The corner frequency of the LC filter is chosen based on the power

supply switching frequency, which is between 100 kHz and 300 kHz in most applications.

Capacitors C1 and C2 are large electrolytic capacitors to provide the basic cutoff frequency of the LC filter. For

example, the cutoff frequency of the combination of these elements might fall between 5 kHz and 50 kHz. Capaci-

tor C3 is a smaller ceramic capacitor designed to provide a low-impedance path for a wide range of high-frequency

signals at the analog power supply pins of the device. The physical location of capacitor C3 must be as close to the

device lead as possible. Multiple instances of capacitors C3 can be used if necessary. The recommended filter for

the HSI macro is shown below: L = 4.7

µH, RL = 1 Ω, C1 = 0.01 µF, C2 = 0.01 µF, C3 = 4.7 µF.

5-9344(F).a

Figure 16. Sample Power Supply Filter Network for Analog LI Power Supply Pins

TO DEVICE

VDD33, VDD33_A[7:4]

VSS, VSS33_A[7:4]

FROM POWER

SUPPLY SOURCE

ORLI10G Datasheet(PDF) 33 Page - Agere Systems