LTC5510 datasheet(20/30 Pages) LINER

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LTC5510

5510fa

For more information www.linear.com/LTC5510

APPLICATIONS INFORMATION

5510 F08

32mA

LTC5510

OUT+

OUT–

VCC

Figure 8. Output Interface

Figure 9. Output Port Equivalent Circuit

5510 F09

LTC5510

OUT+

OUT–

245

0.4pF

0.2pF

1.2nH

OUT Port Interface

The differential output interface is shown in Figure 8.

The OUT+ and OUT– pins are open collector outputs with

internal load resistors that provide a 245Ω differential

output resistance at low frequencies.

Figure 9 shows the equivalent circuit of the output and

Table4listsdifferentialimpedancesforvariousfrequencies.

The impedance values are listed in parallel equivalent form,

with equivalent capacitances also shown. For optimum

single-ended performance, the differential output signal

must be combined through an external transformer or a

discretebaluncircuit.Inapplicationswheredifferentialfilters

or amplifiers follow the mixer, it is possible to eliminate

the transformer and drive these components differentially.

Table 4. Differential OUT Port Impedance

FREQUENCY

(MHz)

IMPEDANCE (Ω)

REFL. COEFF.

REAL*

IMAG* (CAP)

MAG

ANG

245

–j240k (0.67pF)

0.66

0.0

244

–j40k (0.40pF)

0.66

–0.2

244

–j5.31k (0.60pF)

0.66

–1.1

100

245

–j2.66k (0.60pF)

0.66

–2.3

300

243

–j884 (0.60pF)

0.66

–6.8

500

240

–j529 (0.60pF)

0.66

–11

1000

224

–j260 (0.61pF)

0.65

–23

1500

201

–j169 (0.63pF)

0.63

–35

2000

171

–j122 (0.65pF)

0.60

–48

2500

138

–j93 (0.69pF)

0.57

–62

3000

104

–j73 (0.73pF)

0.53

–78

3500

–j59 (0.77pF)

0.48

–97

4000

–j51 (0.78pF)

0.43

–120

4500

–j59 (0.60pF)

0.39

–148

5000

j4.74K

0.38

180

6000

j51

0.44

117

* Parallel Equivalent

Output Matching: High Frequency Output Board

Thehighfrequency(HF)outputevaluationboard(DC1983A)

showninFigure3aisdesignedtousemultilayerchiphybrid

baluns at the output. This board is intended for frequen-

cies above about 800MHz (limited by balun availability).

These baluns deliver good performance and are smaller

than wire-wound baluns. The board is configured for the

matching topology shown in Figure 10. Inductors L1 and

L2 are used to tune out the parasitic output capacitance,

whilethetransformerprovidesdifferentialtosingle-ended

conversion and impedance transformation. The DC bias

to the mixer core can be applied through the matching

inductors. Each pin draws approximately 32mA of DC

supply current.

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