HDMP-1012 datasheet(38/42 Pages) HP

38 / 42 page

610

ground plane, assuming that it is

a fairly clean ground plane. Thus,

all of the separate grounds

(HGND, GND, and ECLGND) can

be connected onto this plane. The

bypassing of VEE to ground

should be accomplished with a

capacitor (C1) of 0.1

µF and a

series resistor (R1) of 10

Ω. This

series RC network prevents

possible oscillations caused by

package, capacitor, and layout

parasitics. The Rx ECLGND leads

are grounded using R2. These 10

Ω resistors reduce excessive

ringing caused by current spikes

generated by the parasitic

inductance in the ECLGND leads.

This effect is more pronounced in

the receiver because of its

multiple ECL outputs.The

ECLGND pins of the Tx are

simply grounded.

In some instances, if the VCO of

either the Tx or the Rx are at the

extreme high end, the frequency

of STRBOUT exceeds the

maximum frequency allowed by

the hosts. In this case, it is

recommended that a diode clamp,

D1, be used across the integrating

cap C2, such that the upper

frequency is limited. The typical

swing of C2 is

± 0.8 volts, and

thus, the clamping diode should

have a turn-on voltage below 0.8

V, such as with germanium or

schottky diodes. This will vary

with each application. This diode

will also aid the Tx and Rx in the

initial frequency lock-in process.

Electrical Connections

The electrical I/Os for both the Tx

and Rx are shown in Figures 21-

23. The data sheet uses the

prefix, I and O, on the logic type

in order to identify input and

output lines respectively.

Additional information on pin

names and their functions can be

Figure 20. Power Supply Bypass.

TOP VIEW

PIN 1

VEE

CAP0B

CAP0A

CAP1A

CAP1B

HGND

VEE

GND

VEE

ECLGND

GND

VEE

GND

VEE

ECLGND

R1 = VEE BYPASS DAMPING RESISTOR

R2 = ECLGND DAMPING RESISTOR

C1 = VEE BYPASS CAPACITOR

C2 = PLL INTEGRATOR CAPACITOR

D1 = OPTIONAL CLAMPING DIODE

10 OHMS

0.1 µF

TOP VIEW

PIN 1

VEE

CAP0B

CAP0A

CAP1A

CAP1B

HGND

VEE

GND

VEE

GND

VEE

HDMP-1012 Datasheet(PDF) 38 Page - Agilent(Hewlett-Packard)

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