Datasheet

INP
INM
VCM
1:1 1:1
50 W
50 W
50 W
50 W
0.1 Fm
0.1 Fm
S0164-05
ADS62P4x
R
G
R
F
R
F
R
FIL
R
FIL
C
FIL
C
FIL
R
G
0.1 Fm
0.1 Fm
0.1 Fm
0.1 Fm
0.1 Fm
0.1 Fm
0.1 Fm
10 Fm
10 Fm
R
S
R
S T
||R
R
T
+V
S
CM
INP
INM
ADS62P4x
THS4509
VCM
500 W
200 W
200 W
5 W
5 W
500 W
0.1 Fm
–V
S
S0259-02
ADS62P45, ADS62P44
ADS62P43, ADS62P42
SLAS561C –JULY 2007– REVISED FEBRUARY 2012 www.ti.com
Figure 87. Drive Circuit at High Input Frequencies
Using Differential Amplifier Drive Circuits
Figure 88 shows a drive circuit using a differential amplifier (TI's THS4509) to convert a single-ended input to
differential output that can be interface to the ADC analog input pins. In addition to the single-ended to differential
conversion, the amplifier also provides gain (10 dB). R
FIL
helps to isolate the amplifier outputs from the switching
input of the ADC. Together with C
FIL
it also forms a low-pass filter that band-limits the noise (and signal) at the
ADC input. As the amplifier output is ac-coupled, the common-mode voltage of the ADC input pins is set using
two 200-Ω resistors connected to VCM.
The amplifier output can also be dc-coupled. Using the output common-mode control of the THS4509, the ADC
input pins can be biased to 1.5 V. In this case, use +4-V and –1-V supplies for the THS4509 so that its output
common-mode voltage (1.5 V) is at mid-supply.
Figure 88. Drive Circuit Using the THS4509
50 Submit Documentation Feedback Copyright © 2007–2012, Texas Instruments Incorporated
Product Folder Link(s): ADS62P45, ADS62P44 ADS62P43, ADS62P42