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
ADS4122, ADS4125
ADS4142, ADS4145
www.ti.com SBAS520A –FEBRUARY 2011– REVISED MARCH 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 104 and Figure 105).
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 102 and Figure 103 show the impedance (Z
IN
= R
IN
|| C
IN
) looking into the ADC input pins.
Figure 102. ADC Analog Input Resistance (R
IN
) Across Frequency
Figure 103. ADC Analog Input Capacitance (C
IN
) Across Frequency
Copyright © 2011, Texas Instruments Incorporated Submit Documentation Feedback 59
Product Folder Link(s): ADS4122 ADS4125 ADS4142 ADS4145