THS1215CPWR datasheet(13/22 Pages) TI

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THS1215

VS+

VS−

RSW

VCM

S t

CLK

In(256)

–R

VIN+

VIN−

−

THS1215

AIN+

AIN−

REFT

REFB

AVDD

THS1215

SLAS292A – MARCH 2001 – REVISED MARCH 2004

Figure 16. Simplified Equivalent Input Circuit

To maintain the frequency performance outlined in the specifications, the total source impedance should be

limited to the following equation with fCLK = 15 MHz, CI = 5 pF, RSW = 200 Ω:

So, for applications running at a lower fCLK, the total source resistance can increase proportionally.

The analog input of the THS1215 is a differential input that can be configured in various ways depending on the

signal source and the required level of performance. A fully differential connection (see Figure 17) delivers the

best performance from the converter.

Figure 17. AC-Coupled Differential Input

The analog input can be dc-coupled (see Figure 18) as long as the inputs are within the analog input common

mode voltage range. For example (see Figure 18), VIN+ and VIN- are signals centered on GND with a

peak-to-peak voltage of 2 V, and the circuit in Figure 18 is used to interface it with the THS1215. Assume AVDD

THS1215CPWR Datenblatt(PDF) 13 Page - Texas Instruments