ADS1675 datasheet(21/40 Pages) TI2

21 / 40 page

100

120

140

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NormalizedFrequency(f /f

)

IN DATA

0.000010

0.0000

0.05 0.10

0.15

0.20

0.45

NormalizedFrequency(f /f

)

IN DATA

0.25

0.30

0.35

0.40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

NormalizedFrequency(f /f

)

IN DATA

ADS1675

www.ti.com

SBAS416D – DECEMBER 2008 – REVISED AUGUST 2010

Phase Response

The

Low-Latency

filter

uses

multiple-stage,

linear-phase digital filter. Linear phase filters exhibit

constant delay time versus input frequency (also

know as constant group delay). This feature of linear

phase filters means that the time delay from any

instant of the input signal to the corresponding same

instant of the output data is constant and independent

of the input signal frequency. This behavior results in

essentially

zero

phase

error

when

measuring

multi-tone signals.

WIDE-BANDWIDTH FILTER

The Wide-Bandwidth (WB) filter is well-suited for

measuring high-frequency ac signals. This digital filter

Figure 43. Frequency Response of

offers

excellent

passband

and

stop

band

Wide-Bandwidth Filter

characteristics.

blank

The DRATE[2:0] digital input pins select from the four

data rates available with the WB filter, as shown in

Table 6. Note that the START pin must be strobed

after a change to the data rate. If a conversion is in

process during a data rate change, the output data

for that conversion are not valid and should be

discarded.

While using the Wide-Bandwidth filter path, the

LL_CONFIG pin must be set to logic high. Setting

LL_CONFIG low forces the ADS1675 to switch to a

low-latency filter path, overriding the FPATH pin.

Table 6. Wide-Bandwidth Data Rates

DATA

–3dB

DRATE

RATE

SETTLING TIME,

BANDWIDTH

[2:0]

(kSPS)

tSETTLE-LL

(kHz)

Figure 44. Passband Response for

000

125

439.44ms

14062tCLK

59.375

Wide-Bandwidth Filter

001

250

219.81ms

7074tCLK

118.75

010

500

110.00ms

3520tCLK

237.5

011

1000

55.04ms

1763tCLK

475

100

2000

27.52ms

2642tLSCLK

950

101

4000

13.79ms

1324tLSCLK

1900

1. The input signal aliases when its frequency

exceeds fDATA/2, in accordance with the Nyquist

theorem.

Frequency Response

Figure 43 shows the frequency response for the

Wide-Bandwidth filter path normalized to the output

data rate, fDATA. Figure 44 shows the passband ripple,

and the transition from passband to stop band is

illustrated in Figure 45. These three plots are valid for

all of the data rates available on the ADS1675.

Figure 45. Transition Band Response for

Simply substitute the selected data rate to express

Wide-Bandwidth Filter

the x-axis in absolute frequency.

Submit Documentation Feedback

Product Folder Link(s): ADS1675

ADS1675 Datasheet(PDF) 21 Page - Texas Instruments

ADS1675 Datasheet(HTML) 21 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Datasheet Download

Link URL