7

SY89529L

Micrel, Inc.

M9999-110405

hbwhelp@micrel.com or (408) 955-1690

Power Supply Filtering Techniques

As in any high speed integrated circuits, power supply

filtering is very important. V

V

plane through vias, and bypass capacitors should be used for

each pin. To achieve optimum jitter performance, better

power-supply isolation is required. In this case a ferrite bead

along with a 1

µF and a 0.01µF bypass capacitor should be

connected to each power supply pin. Figure 6 illustrates

power-supply filtering using ferrite beads and bypass

capacitors.

use ferrite bead = 200mA, 0.45

Ω DC,

Murata P/N BLM21A1025

Ω DC,

Murata, P/N BLM31P005

*Componet sizs: 0805

1

µF

22

µF

0.01

µF

Ferrite Bead*

“Power Supply”

side

“Device”

side

Pins

Figure 5. Power Supply Filtering

Termination for PECL Outputs

The differential PECL outputs, FOUT and /FOUT, are low-

impedance emitter-follower outputs. Therefore, terminating

resistors (DC current path to ground) or current sources must

be used for functionality. These outputs are designed to drive

50

Ωtransmissionlines.Matchedimpedancetechniquesshould

be used to maximize operating frequency and minimize signal

distortion. There are a few simple termination schemes.

Figure 7 shows a common 3-resistor termination scheme. For

more termination examples, see Micrel’s Application Note 9

online at www.micrel.com.

z = 50

Ω

Low impedance,

emitter-follower outputs

z = 50

Ω

50

Ω

FOUT

/FOUT

50

Ω

SY89529L

3-resistor network

available*

*3-resistor network = Thin-film Technologies,

P/N TFT-RN1632-AN1DNC

50

Ω

Figure7. LVPECL Output Termination