ADS6445 datasheet(48/75 Pages) STMICROELECTRONICS

48 / 75 page

www.ti.com

M0087-01

Frequency(100kHzto500MHz)

Freq=50MHz

S(1,1)=0.967/ –13.241

Impedance=62.211 – j421.739

Freq=400MHz

S(1,1)=0.273/ –59.329

Impedance=58.132 – j29.510

100

200

300

400

500

600

700

800

900

1000

100

150

200

250

300

350

400

450

500

f -- Input Frequency -- MHz

Frequency = 50 MHz

Mag(Zin1) = 426.302

Frequency = 400 MHz

Mag(Zin1) = 65.193

Using RF-Transformers Based Drive Circuits

ADS6445, ADS6444

ADS6443, ADS6442

SLAS531 – MAY 2007

APPLICATION INFORMATION (continued)

Figure 84. ADC Input Impedance, Zin

Figure 85 shows a configuration using a single 1:1 turns ratio transformer (for example, Coilcraft WBC1-1) that

can be used for low input frequencies up to 100 MHz.

The single-ended signal is fed to the primary winding of the RF transformer. The transformer is terminated on

the secondary side. Putting the termination on the secondary side helps to shield the kickbacks caused by the

sampling circuit from the RF transformer’s leakage inductances. The termination is accomplished by two

resistors connected in series, with the center point connected to the 1.5 V common mode (VCM pin). The value

of the termination resistors (connected to common mode) has to be low (< 100

Ω) to provide a low-impedance

path for the ADC common-mode switching current.

Submit Documentation Feedback

ADS6445 Datasheet(PDF) 48 Page - STMicroelectronics

ADS6445 Datasheet(HTML) 48 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

Datasheet Download

Link URL