Micrel, Inc.

SY89856U

August 2007

10

M9999-082907-C

LVPECL Output Interface Applications

LVPECL has a high input impedance and 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

may be left floating. However, single-ended outputs

must be terminated, or balanced.

R2

82

R2

82

+3.3V

+3.3V

R1

130

R1

130

+3.3V

Notes:

1. For 2.5V systems, R1 = 250

Ω, R2 = 62.5Ω.

Figure 4a. Parallel Termination-Thevenin Equivalent

Z

Z

+3.3V

+3.3V

destination

source

Rb C1

0.01µF

(optional)

Notes:

2. Power-saving alternative to Thevenin termination.

3. Place termination resistors as close to destination inputs

as possible.

Figure 4b. Parallel Termination (3-Resistors)

Related Documentation

Part Number

Function

Data Sheet Link

SY58035U

4.5GHz, 1:6 LVPECL Fanout Buffer with

2:1 MUX Input and Internal Termination

www.micrel.com/product-info/products/sy58035u.html

HBW Solutions

New Products and Applications

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