OP4008B datasheet(3/5 Pages) RFM

3 / 5 page

669.327 MHz

Optical Timing Clock

RF Monolithics, Inc.

Phone: (972) 233-2903

Fax: (972) 387-8148

E-mail: info@rfm.com

Page 3 of 5

RFM Europe

Phone: 44 1963 251383

Fax: 44 1963 251510

http://www.rfm.com

OP4008B-041003

Load Recommendations for the OP4008B

The Q and Q outputs of RFM's OPB-series of SAW

clocks are AC-coupled internally. This allows customers

to set the DC level of the outputs with a simple resistor

pair on each output to drive most any application.

3.3V

Load

OP4005B

LOAD

VDC

TUNE

load x R1

R1 + R2

1 + 1 = 1

R1 R2

Vdc=

Load Type

Vdc

Vload

10k 3.3 V PECL

1.95

120

3.3 V

100k 3.3 V PECL

1.88

120

3.3 V

10k 5 V PECL

3.65

180

5.0 V

100k 5 V PECL

3.58

180

5.0 V

10k -5 V NECL

-1.30

240

-5.0 V

100k -5 V NECL

-1.42

240

-5.0 V

Note that the OPB parts will drive negative ECL loads by applying negative voltage to the Vload points in the circuit.

Vdc is the DC level desired on the outputs.

Vload is the DC supply on the load resistors (typically 3.3 V).

Equations 1 & 2 describe the voltage divider created by R1 & R2 and the equilivent load impedence set by the parrellel com-

bination of R1 & R2.

A given load type will have specifications that set Vdc. Choose an available Vload that is 2x to 3x larger than the desired Vdc.

This will allow R1 to be expressed in terms of R2 as in equation 1. By substituting this result in equation 2, a value for R2

will result. Solving equation 1 for R1 with the known R2 is the last step.

Table 1 has some typical values for Vdc & Vload for various ECL loads along with R1 & R2 values that are standard.

OP4008B Datasheet(PDF) 3 Page - RF Monolithics, Inc

OP4008B Datasheet(HTML) 3 Page - RF Monolithics, Inc

Html Pages

1 2 3 4 5

Datasheet Download

Link URL