CLC014 datasheet(10/18 Pages) NSC

10 / 18 page

Output Interfacing (Continued)

may be used. The resistive divider network provides 75

Ω ter-

mination and establishes proper ECL levels. This circuit con-

sumes slightly more power than the previous circuits.

Design Guidelines

SELECTING THE AUTOMATIC EQUALIZER CAPACITOR

The AEC capacitor sets the loop time constant

τ for the

equalizer’s adaptive loop response time. The following for-

mula is used to set the loop time constant:

τ =R • C

AEC • 10

−6

R is a conversion factor that is set by internal equalizer pa-

rameters and cable length. For Belden 8281 coaxial cable,

the R values are (

τ = µs, C

AEC in pF):

Cable

Length

R Value

(Ohms)

100 meters

15000

200 meters

20000

300 meters

32000

For example, a C

AEC value of 100 pF results in an adaptive

loop time constant of 2 µs at 200 meters of cable.

CONNECTION AND OPERATION OF CD AND MUTE

Carrier Detect (CD) is a CMOS output that indicates the

presence of equalized data from the filter. This CD output

can be connected to MUTE to suspend changes in the data

outputs DO and DO, if no valid signal exists. This simple

configuration prevents random output transitions due to

noise. For sparse transition patterns it is recommended that

a capacitor be connected to CD as shown in

Figure 1.

Add a capacitor to pin 5 to slow the response time of Carrier

Detect when Carrier Detect is connected to MUTE. The ca-

pacitor reduces sensitivity to pathological patterns. Patho-

logical patterns are defined as sparse data sequences with

few transitions.

OUTPUT EYE MONITOR OEM CONNECTIONS

The OEM is a high-speed, buffered output for monitoring the

equalized eye pattern prior to the output comparator. Its out-

put is designed to drive an AC-coupled 50

Ω coaxial cable

with a series 50

Ω backmatch resistor. The cable should be

terminated with 50

Ω at the oscilloscope. Figure 1 shows a

schematic with a typical connection.

MINIMUM DATA TRANSITIONS

The CLC014 specifies a minimum transition rate. For the

CLC014 this sets the minimum data rate for transmitting data

through any cable medium. The CLC014 minimum average

transition density is found in the Electrical Characteristics

section of the datasheet.

POWER SUPPLY OPERATION AND THERMAL

CONSIDERATIONS

The CLC014 operates from either +5V or −5.2V single sup-

plies. Refer to

Figure 1 when operating the part from +5V.

When operating with a −5.2V supply, the V

EE pins should be

bypassed to ground. The evaluation board and associated

literature provide for operation from either supply.

Maximum power dissipation occurs at minimum cable

length. Under that condition, I

CC =58mA.

Total power dissipated:

T = (58 mA)(5V) = 290 mW

Power in the load:

L = (0.7V)(11 mA) + (37.5)(11 mA)

2 =12mW

Maximum power dissipated on the die:

DMAX =PT–PL = 278 mW

Junction Temperature =

(

JA)(278 mW) + TA =T A + 26˚C

DS100056-27

FIGURE 7. Alternative Load Terminated

Output Interface

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