Datasheet

100
10
1.00
0.10
0.01
.00
.00
InputFrequency(GHz)
0 1.0
DifferentialInputResistance(k )W
0.30.20.1 0.4 0.5 0.6 0.7 0.8 0.9
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
InputFrequency(GHz)
0 1.0
DifferentialInputCapacitance(pF)
0.30.20.1 0.4 0.5 0.6 0.7 0.8 0.9
ADS4126 , ADS4129
ADS4146 , ADS4149
www.ti.com SBAS483G – NOVEMBER 2009–REVISED JANUARY 2011
In the ADS412x/4x, the R-C component values have been optimized while supporting high input bandwidth
(550MHz). However, in applications where very high input frequency support is not required, filtering of the
glitches can be improved further with an external R-C-R filter; see Figure 116 and Figure 117).
In addition, the drive circuit may have to be designed to provide a low insertion loss over the desired frequency
range and matched impedance to the source. While designing the drive circuit, the ADC impedance must be
considered. Figure 114 and Figure 115 show the impedance (Z
IN
= R
IN
|| C
IN
) looking into the ADC input pins.
Figure 114. ADC Analog Input Resistance (R
IN
) Across Frequency
Figure 115. ADC Analog Input Capacitance (C
IN
) Across Frequency
Copyright © 2009–2011, Texas Instruments Incorporated Submit Documentation Feedback 59
Product Folder Link(s): ADS4126 ADS4129 ADS4146 ADS4149