THS0842 Datasheet, PDF (20/29 Pages) Texas Instruments – DUAL-INPUT, 8-BIT, 40 MSPS LOW-POWER ANALOG-TO-DIGITAL CONVERTER WITH SINGLE OR DUAL PARALLEL BUS OUTPUT

THS0842
DUAL-INPUT, 8-BIT, 40 MSPS LOW-POWER ANALOG-TO-DIGITAL CONVERTER
WITH SINGLE OR DUAL PARALLEL BUS OUTPUT
SLAS246 – DECEMBER 1999
PRINCIPLES OF OPERATION
analog input (continued)
Positive
Analog
Input
I/Q+
1.5 + 0.25 V
1.5 V
I/Q+
1.5 – 0.25 V
Negative
Analog
Input
I/Q–
1.5 – 0.25 V
1.5 V
I/Q–
1.5 + 0.25 V
+0.5 V
Differential
0V
Input
1.0 Vp–p
–0.5 V
Figure 19. Differential Input Waveform
The analog input can be dc coupled (Figure 21) as long as the inputs are within the analog input common mode
voltage range. The resistors, R, in Figure 21 are not absolutely necessary but may be used as load setting
resistors. A capacitor, C, connected from I/Q IN+ to I/Q IN– will help filter any high frequency noise on the inputs,
also improving performance. Note, that the chosen value of capacitor C must take into account the highest
frequency component of the analog input signal.
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