Micrel, Inc.

SY89850U

August 2007

9

M9999-083007-B

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

Output Interface Applications

LVPECL has a high input impedance, a very low

output impedance (open emitter), and a small signal

swing which results in low EMI. LVPECL is ideal for

driving

50

Ω - and 100

Ω -controlled

impedance

transmission lines. There are several techniques for

terminating the LVPECL output: Parallel Termination-

Thevenin Equivalent, Parallel Termination (3-resistor),

and AC-coupled Termination. Unused output pairs

must be terminated, or balanced.

Note:

1.

For +2.5V systems, R1 = 250

Ω, R2 = 62.5Ω.

Figure 4a. Parallel Termination-Thevenin Equivalent

Notes:

1. Power-saving alternative to Thevenin termination.

2. Place termination resistors as close to destination inputs as possible.

Ω.

Figure 4b. Parallel Termination (3-Resistor)

Related Product and Support Documentation

Part Number

Function

Data Sheet Link

SY58601U

Ultra-Precision Differential 800mV LVPECL

Line Driver/Receiver with Internal Termination

www.micrel.com/product-info/products/sy58601u.shtml

HBW Solutions

New Products and Applications

www.micrel.com/product-info/products/solutions.shtml