REV. A

AD7707

–9–

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

24816

32

64

128

MCLK IN = 2.4576 MHz

10 Hz

2.62 Hz

1.47 (16)

0.95 (16)

0.88 (16)

0.55 (16)

0.42 (16)

0.42 (16)

0.42 (15)

0.41 (14)

50 Hz

13.1 Hz

4.2 (16)

2.6 (16)

1.6 (16)

1 (16)

0.89 (15.5) 0.94 (15)

0.9 (14)

0.9 (13)

60 Hz

15.72 Hz

4.9 (16)

3 (16)

1.8 (16)

1.1 (16)

1 (15.5)

1 (14.5)

0.94 (14)

0.94 (13)

250 Hz

65.5 Hz

104 (13)

52 (13)

26 (13)

14 (13)

6.5 (13)

4.1 (12.5)

2.7 (12.5)

2.3 (11.5)

500 Hz

131 Hz

572 (10.5) 293 (10.5)

125 (10.5)

69 (10.5)

40 (10.5)

19 (10.5)

10 (10.5)

5.9 (10)

MCLK IN = 1 MHz

4.05 Hz

1.06 Hz

1.48 (16)

8.95 (16)

0.87 (16)

0.67 (16)

0.41 (16)

0.40 (16)

0.40 (15)

0.40 (14)

20 Hz

5.24 Hz

3.9 (16)

2.46 (16)

1.77 (16)

1.19 (16)

0.94 (16)

0.93 (15)

0.95 (14)

0.9 (13)

25 Hz

6.55 Hz

5.37 (16)

3.05 (16)

1.89 (16)

1.33 (16)

1.11 (15.5) 1.06 (14.5) 1.04 (13.5) 1.02 (12.5)

100 Hz

26.2 Hz

98.9 (13)

52.4 (13)

26.1 (13)

12.7 (13)

6.08 (13)

4.01 (12.5) 2.62 (12.5) 2.33 (11.5)

200 Hz

52.4 Hz

596 (10.5) 298 (10.5)

133 (10.5)

69.3 (10.5) 34.7 (10.5) 16.9 (10.5) 9.67 (10.5) 6.34 (10)

OUTPUT NOISE FOR LOW LEVEL INPUT CHANNELS (3 V OPERATION)

Table III shows the AD7707 output rms noise and peak-to-peak resolution in unbuffered mode 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 bipolar input ranges

IV shows the rms noise and peak-to-peak resolution when operating in unbuffered mode. It is important to note that the peak-to-peak

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.

are typical and are rounded to the nearest LSB. The numbers apply for the CLK DIV bit of the Clock Register set to 0. 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 III. Output RMS Noise/Peak-to-Peak Resolution vs. Gain and Output Update Rate @ +3 V

AIN1 and AIN2 Unbuffered 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

24816

32

64

128

MCLK IN = 2.4576 MHz

10 Hz

2.62 Hz

1.60 (16)

0.8 (16)

0.48 (16)

0.29 (16)

0.29 (16)

0.27 (15.5) 0.26 (14.5) 0.26 (13.5)

50 Hz

13.1 Hz

3.8 (16)

1.9 (16)

1.1 (16)

0.64 (16)

0.60 (15.5) 0.6 (14.5)

0.6 (13.5)

0.6 (12.5)

60 Hz

15.72 Hz

4.4 (16)

2.2 (16)

1.35 (16)

0.78 (16)

0.7 (15)

0.68 (14.5) 0.64 (13.5) 0.64 (12.5)

250 Hz

65.5 Hz

53 (13)

24 (13)

15 (13)

6.8 (13)

3.6 (12.5)

2.1 (12.5)

1.5 (12)

1.3 (11)

500 Hz

131 Hz

300 (10.5) 138 (10.5)

80 (10.5)

34 (10.5)

18 (10.5)

8.7 (10.5)

4.8 (10)

3.4 (10)

MCLK IN = 1 MHz

4.05 Hz

1.06 Hz

1.56 (16)

0.88 (16)

0.52 (16)

0.3 (16)

0.28 (16)

0.27 (15.5) 0.27 (14.5) 0.26 (13.5)

20 Hz

5.24 Hz

3.85 (16)

2.02 (16)

1.15 (16)

0.74 (16)

0.63 (15.5) 0.57 (14.5) 0.61 (13.5) 0.58 (12.5)

25 Hz

6.55 Hz

4.56 (16)

2.4 (16)

1.4 (16)

0.79 (16)

0.68 (15)

0.66 (14.5) 0.64 (13.5) 0.64 (12.5)

100 Hz

26.2 Hz

45.7 (13)

22 (13)

13.7 (13)

5.27 (13)

2.64 (13)

2 (12.5)

1.59 (12)

1.4 (11)

200 Hz

52.4 Hz

262 (10.5) 125 (10.5)

66 (10.5)

32.4 (10.5) 18.4 (10.5) 8.6 (10.5)

4.64 (10.5) 3.3 (10)