REV. A

AD7707

–11–

Table VI. Output RMS Noise/ Peak-to-Peak Resolution vs. Gain and Output Update Rate @ +5 V

AIN3 Buffered Mode Only

Filter First

10 V Range

5 V Range

0 V to +10 V Range

0 to +5 V Range

Notch and O/P

–3 dB

RMS Noise P-P (Bits)

RMS Noise P-P (Bits)

RMS Noise P-P (Bits)

RMS Noise P-P (Bits)

Data Rate

Frequency

( V)

Resolution ( V)

Resolution ( V)

Resolution

( V)

Resolution

MCLK IN = 2.4576 MHz

10 Hz

2.62 Hz

7.4

16

5.2

16

7.4

16

5.2

16

50 Hz

13.1 Hz

22.2

16

14.3

16

22.2

16

14.3

16

60 Hz

15.72 Hz

26.6

16

15.85

16

26.6

16

15.85

16

250 Hz

65.5 Hz

475

13

187

13

475

12

187

12

500 Hz

131 Hz

2423

10.5

1097

10.5

2423

9.5

1097

9.5

MCLK IN = 1 MHz

4.05 Hz

1.06 Hz

7.63

16

5.45

16

7.63

16

5.45

16

20 Hz

5.24 Hz

20.25

16

13.3

16

20.25

16

13.3

16

25 Hz

6.55 Hz

23.5

16

14.6

16

23.5

16

14.6

15.5

100 Hz

26.2 Hz

377

13

210

13

377

12

210

12

200 Hz

52.4 Hz

2226

10.5

1132

10.5

2226

9.5

1132

9.5

OUTPUT NOISE FOR HIGH LEVEL INPUT CHANNEL AIN3 (5 V OPERATION)

Table VII shows the AD7707 output rms noise and peak-to-peak resolution for the selectable notch and –3 dB frequencies for the

part, as selected by FS0, FS1 and FS2 of the Clock Register. The numbers given are for the

±5 V, 0 V to +5 V and 0 V to +10 V

ated at an analog input voltage of 0 V for unbuffered mode of operation. The above operating ranges are only achievable in unbuf-

fered mode when operating at 3 V due to common-mode limitations on the input amplifier. It is important to note that these numbers

represent the resolution for which there will be no code flicker. They are not calculated based on rms noise but on peak-to-peak noise. Operating

at a gain of 1 in unipolar mode provides a range of 0 V to +10 V. Operating the high level channel with a gain of 2 in bipolar mode

provides a

±5 V operating range. Operating at a gain of 2 in unipolar mode provides an operating range of 0 V to +5 V. The output

noise comes from two sources. The first is the electrical noise in the semiconductor devices (device noise) used in the implementation

of the modulator. Secondly, when the analog input is converted into the digital domain, quantization noise is added. The device

noise is at a low level and is independent of frequency. The quantization noise starts at an even lower level but rises rapidly with

increasing frequency to become the dominant noise source. The numbers in the tables are given for the bipolar input ranges. For the

unipolar ranges the rms noise numbers will be the same as the bipolar range but the peak-to-peak resolution is now based on half the

signal range which effectively means losing 1 bit of resolution.

Table VII. Output RMS Noise/ Peak-to-Peak Resolution vs. Gain and Output Update Rate @ +3 V

AIN3 Unbuffered Mode Only

Filter First

0 V to +10 V Range

5 V Range

0 to +5 V Range

Notch and O/P

–3 dB

RMS Noise

P-P (Bits)

RMS Noise

P-P (Bits)

RMS Noise

P-P (Bits)

Data Rate

Frequency

( V)

Resolution

( V)

Resolution

( V)

Resolution

MCLK IN = 2.4576 MHz

10 Hz

2.62 Hz

12.4

16

7.02

16

7.02

16

50 Hz

13.1 Hz

30.35

16

16.4

16

16.4

15.5

60 Hz

15.72 Hz

34.55

16

19.13

16

19.13

15

250 Hz

65.5 Hz

498

12.5

204

13

204

12

500 Hz

131 Hz

2266

10.5

1151

10.5

1151

9.5

MCLK IN = 1 MHz

4.05 Hz

1.06 Hz

13.9

16

7.3

16

7.3

16

20 Hz

5.24 Hz

32.2

16

17.4

16

17.4

15

25 Hz

6.55 Hz

33.4

16

18.57

16

18.57

15

100 Hz

26.2 Hz

430

13

200

13

200

12

200 Hz

52.4 Hz

2207

10.5

1048

10.5

1048

9.5