REV. A

AD7707

–10–

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

AIN1 and AIN2 Buffered Mode Only

Filter First

Typical Output RMS Noise in

V (Peak-to-Peak Resolution in Bits)

Notch and O/P

–3 dB

Gain of

Gain of

Gain of

Gain of

Gain of

Gain of

Gain of

Gain of

Data Rate

Frequency 1

2

4

8

16

32

64

128

MCLK IN = 2.4576 MHz

10 Hz

2.62 Hz

1.80 (16)

1 (16)

0.7 (16)

0.41 (16)

0.41 (16)

0.41 (15)

0.41 (14)

0.41 (13)

50 Hz

13.1 Hz

4.1 (16)

2.4 (16)

1.5 (16)

1 (15.5)

0.91 (15)

0.89 (14)

0.86 (13)

0.83 (12)

60 Hz

15.72 Hz

5.1 (16)

3 (16)

1.8 (16)

1.1 (15.5)

0.94 (14.5) 0.94 (13.5) 0.99 (13)

0.99 (11.5)

250 Hz

65.5 Hz

50 (13)

27 (13)

12.3 (13)

6.4 (13)

4 (12.5)

2.7 (12.5)

2.2 (11.5)

1.8 (11)

500 Hz

131 Hz

275 (10.5) 125 (10.5)

80 (10.5)

39 (10.5)

16 (10.5)

8.9 (10.5)

5.2 (10)

4.2 (9.5)

MCLK IN = 1 MHz

4.05 Hz

1.06 Hz

1.75 (16)

1.18 (16)

0.67 (16)

0.44 (16)

0.41 (16)

0.44 (15)

0.43 (14)

0.43 (13)

20 Hz

5.24 Hz

4.21 (16)

2.5 (16)

1.48 (16)

1 (15.5)

0.94 (15)

0.96 (14)

0.89 (13)

0.86 (12)

25 Hz

6.55 Hz

5.15 (16)

2.8 (16)

1.8 (16)

1.15 (15.5) 1 (14.5)

1.02 (13.5) 0.96 (13)

1.03 (11.5)

100 Hz

26.2 Hz

46.1 (13)

24.3 (13)

13.6 (13)

6.71 (13)

4.1 (12.5)

2.54 (12.5) 2.3 (11.5)

2.15 (10.5)

200 Hz

52.4 Hz

282 (10.5) 123 (10.5)

66 (10.5)

35.3 (10.5) 14.8 (10.5) 9.91 (10.5) 5.48 (10)

4.01 (9.5)

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

Table V shows the AD7707 output rms noise and peak-to-peak resolution in unbuffered 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

± 10 V,

±5 V, 0 to 5 V and 0 V to +10 V ranges with a V

numbers are typical and are generated at an analog input voltage of 0 V. Table VI meanwhile shows the output rms noise and

peak-to-peak resolution in buffered mode. 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 the high level channel with a gain

of 2 in bipolar mode gives an operating range of

±10 V. Operating at a gain of 2 in unipolar mode gives a range of 0 V to

+10 V. Operating the high level channel with a gain of 4 in bipolar mode gives the

± 5 V operating range. Operating at a gain

of 4 in unipolar mode gives an operating range of 0 V to +5 V. Noise for all input ranges is shown in Appendix 1. The out-

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

AIN3 Unbuffered Mode Only

F

ilter First

10 V Range

5 V Range

0 V to +10 V Range

0 V 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

5.10

16

3.52

16

5.10

16

3.52

16

50 Hz

13.1 Hz

15.82

16

9.77

16

15.82

16

9.77

16

60 Hz

15.72 Hz

20.36

16

12.29

16

20.36

16

12.29

16

250 Hz

65.5 Hz

430

13

212

13

430

12

212

12

500 Hz

131 Hz

2350

10

1287

10

2350

9

1287

9

MCLK IN = 1 MHz

4.05 Hz

1.06 Hz

5.13

16

3.53

16

5.13

16

3.53

16

20 Hz

5.24 Hz

18.9

16

13.25

16

18.9

16

13.25

16

25 Hz

6.55 Hz

23.7

16

15.3

16

23.7

16

15.3

15.5

100 Hz

26.2 Hz

406

13

174

13

406

12

174

12

200 Hz

52.4 Hz

2184

10.5

1144

10.5

2184

9.5

1144

9.5